Write about bacteria. Research work on the topic "Bacteria found on the human skin and their effect on the human body

The content of the article

an extensive group of unicellular microorganisms characterized by the absence of a cell nucleus surrounded by a membrane. At the same time, the genetic material of a bacterium (deoxyribonucleic acid, or DNA) occupies a very specific place in the cell - a zone called the nucleoid. Organisms with this cell structure are called prokaryotes (“pre-nuclear”), in contrast to all the others - eukaryotes (“true nuclear”), whose DNA is located in the nucleus surrounded by a shell.

Bacteria, once considered microscopic plants, are now classified as a separate kingdom, Monera, one of five in the current classification system, along with plants, animals, fungi, and protists.

fossil evidence.

Bacteria are probably the oldest known group of organisms. Layered stone structures - stromatolites - dated in some cases to the beginning of the Archeozoic (Archaean), i.e. that arose 3.5 billion years ago, is the result of the vital activity of bacteria, usually photosynthetic, the so-called. blue-green algae. Similar structures (bacterial films impregnated with carbonates) are still formed, mainly off the coast of Australia, the Bahamas, in the California and Persian Gulfs, but they are relatively rare and do not reach large sizes, because herbivorous organisms, such as gastropods, feed on them. Today, stromatolites grow mainly where these animals are absent due to the high salinity of the water or for other reasons, but before the appearance of herbivorous forms in the course of evolution, they could reach enormous sizes, constituting an essential element of oceanic shallow water, comparable to modern coral reefs. Tiny charred spheres have been found in some ancient rocks, which are also thought to be the remains of bacteria. The first nuclear, i.e. eukaryotic, cells evolved from bacteria about 1.4 billion years ago.

Ecology.

There are many bacteria in the soil, at the bottom of lakes and oceans - everywhere where organic matter accumulates. They live in the cold, when the thermometer is slightly above zero, and in hot acid springs with temperatures above 90 ° C. Some bacteria tolerate very high salinity of the environment; in particular, they are the only organisms found in the Dead Sea. In the atmosphere, they are present in water droplets, and their abundance there usually correlates with the dustiness of the air. So, in cities, rainwater contains much more bacteria than in rural areas. There are few of them in the cold air of the highlands and polar regions; nevertheless, they are found even in the lower layer of the stratosphere at an altitude of 8 km.

The digestive tract of animals is densely populated with bacteria (usually harmless). Experiments have shown that they are not necessary for the life of most species, although they can synthesize some vitamins. However, in ruminants (cows, antelopes, sheep) and many termites, they are involved in the digestion of plant foods. In addition, the immune system of an animal raised in sterile conditions does not develop normally due to the lack of stimulation by bacteria. The normal bacterial "flora" of the intestine is also important for the suppression of harmful microorganisms that enter there.

STRUCTURE AND LIFE OF BACTERIA

Bacteria are much smaller than the cells of multicellular plants and animals. Their thickness is usually 0.5–2.0 µm, and their length is 1.0–8.0 µm. Some forms can barely be seen with the resolution of standard light microscopes (about 0.3 µm), but there are also known species with a length of more than 10 µm and a width that also goes beyond these limits, and a number of very thin bacteria can exceed 50 µm in length. A quarter of a million medium-sized representatives of this kingdom will fit on the surface corresponding to the point set with a pencil.

Structure.

According to the peculiarities of morphology, the following groups of bacteria are distinguished: cocci (more or less spherical), bacilli (rods or cylinders with rounded ends), spirilla (rigid spirals) and spirochetes (thin and flexible hair-like forms). Some authors tend to combine the last two groups into one - spirilla.

Prokaryotes differ from eukaryotes mainly in the absence of a well-formed nucleus and the presence, in a typical case, of only one chromosome - a very long circular DNA molecule attached at one point to the cell membrane. Prokaryotes also lack membrane-bound intracellular organelles called mitochondria and chloroplasts. In eukaryotes, mitochondria generate energy during respiration, and photosynthesis occurs in chloroplasts. In prokaryotes, the entire cell (and, first of all, the cell membrane) takes on the function of the mitochondria, and in photosynthetic forms, at the same time, the chloroplast. Like eukaryotes, inside the bacterium are small nucleoprotein structures - ribosomes necessary for protein synthesis, but they are not associated with any membranes. With very few exceptions, bacteria are unable to synthesize sterols, which are important components of eukaryotic cell membranes.

Outside of the cell membrane, most bacteria are lined with a cell wall, somewhat reminiscent of the cellulose wall of plant cells, but consisting of other polymers (they include not only carbohydrates, but also amino acids and substances specific to bacteria). This shell prevents the bacterial cell from bursting when water enters it due to osmosis. On top of the cell wall is often a protective mucosal capsule. Many bacteria are equipped with flagella, with which they actively swim. Bacterial flagella are simpler and somewhat different than similar eukaryotic structures.

Sensory functions and behavior.

Many bacteria have chemical receptors that detect changes in the acidity of the environment and the concentration of various substances, such as sugars, amino acids, oxygen and carbon dioxide. Each substance has its own type of such “taste” receptors, and the loss of one of them as a result of mutation leads to partial “taste blindness”. Many motile bacteria also respond to temperature fluctuations, and photosynthetic species to changes in light. Some bacteria perceive the direction of magnetic field lines, including the Earth's magnetic field, with the help of magnetite particles (magnetic iron ore - Fe 3 O 4) present in their cells. In water, bacteria use this ability to swim along lines of force in search of a favorable environment.

METABOLISM

Partly due to the small size of bacteria, the intensity of their metabolism is much higher than that of eukaryotes. Under the most favorable conditions, some bacteria can double their total mass and abundance approximately every 20 minutes. This is due to the fact that a number of their most important enzyme systems function at a very high speed. So, a rabbit needs a few minutes to synthesize a protein molecule, and bacteria - seconds. However, in the natural environment, for example, in the soil, most bacteria are "on a starvation diet", so if their cells divide, then not every 20 minutes, but every few days.

Nutrition.

Bacteria are autotrophs and heterotrophs. Autotrophs (“self-feeding”) do not need substances produced by other organisms. They use carbon dioxide (CO 2 ) as the main or only source of carbon. Including CO 2 and other inorganic substances, in particular ammonia (NH 3), nitrates (NO - 3) and various sulfur compounds, in complex chemical reactions, they synthesize all the biochemical products they need.

Heterotrophs (“feeding on others”) use as the main source of carbon (some species also need CO 2) organic (carbon-containing) substances synthesized by other organisms, in particular sugars. Oxidized, these compounds supply energy and molecules necessary for the growth and vital activity of cells. In this sense, heterotrophic bacteria, which include the vast majority of prokaryotes, are similar to humans.

main sources of energy.

If for the formation (synthesis) of cellular components mainly light energy (photons) is used, then the process is called photosynthesis, and the species capable of it are called phototrophs. Phototrophic bacteria are divided into photoheterotrophs and photoautotrophs, depending on which compounds - organic or inorganic - serve as their main source of carbon.

Photoautotrophic cyanobacteria (blue-green algae), like green plants, split water molecules (H 2 O) due to light energy. In this case, free oxygen (1/2 O 2) is released and hydrogen (2H +) is formed, which, one might say, turns carbon dioxide (CO 2) into carbohydrates. In green and purple sulfur bacteria, light energy is not used to break down water, but other inorganic molecules, such as hydrogen sulfide (H 2 S). As a result, hydrogen is also produced, reducing carbon dioxide, but oxygen is not released. Such photosynthesis is called anoxygenic.

Photoheterotrophic bacteria, such as purple nonsulfur bacteria, use light energy to produce hydrogen from organic substances, in particular isopropanol, but gaseous H 2 can also serve as its source.

If the main source of energy in the cell is the oxidation of chemicals, bacteria are called chemoheterotrophs or chemoautotrophs, depending on which molecules serve as the main source of carbon - organic or inorganic. In the former, organics provide both energy and carbon. Chemoautotrophs receive energy from the oxidation of inorganic substances, such as hydrogen (to water: 2H 4 + O 2 ® 2H 2 O), iron (Fe 2+ ® Fe 3+) or sulfur (2S + 3O 2 + 2H 2 O ® 2SO 4 2 - + 4H +), and carbon - from CO 2. These organisms are also called chemolithotrophs, thus emphasizing that they “feed” on rocks.

Breath.

Cellular respiration is the process of releasing chemical energy stored in "food" molecules for its further use in vital reactions. Respiration can be aerobic and anaerobic. In the first case, it needs oxygen. It is needed for the work of the so-called. electron transport system: electrons move from one molecule to another (in this case, energy is released) and ultimately attach to oxygen along with hydrogen ions - water is formed.

Anaerobic organisms do not need oxygen, and for some species of this group it is even poisonous. The electrons released during respiration are attached to other inorganic acceptors, such as nitrate, sulfate or carbonate, or (in one of the forms of such respiration - fermentation) to a certain organic molecule, in particular to glucose.

CLASSIFICATION

In most organisms, a species is considered to be a reproductively isolated group of individuals. In a broad sense, this means that representatives of a given species can produce fertile offspring, mating only with their own kind, but not with individuals of other species. Thus, the genes of a particular species, as a rule, do not go beyond its limits. However, in bacteria, genes can be exchanged between individuals not only of different species, but also of different genera, so it is not entirely clear whether it is legitimate to apply here the usual concepts of evolutionary origin and kinship. In connection with this and other difficulties, a generally accepted classification of bacteria does not yet exist. Below is one of its widely used variants.

THE KINGDOM OF MONERA

Type I. Gracilicutes (thin-walled Gram-negative bacteria)

Class 1. Scotobacteria (non-photosynthetic forms, such as myxobacteria)

Class 2. Anoxyphotobacteria (non-oxygen producing photosynthetic forms, such as purple sulfur bacteria)

Class 3. Oxyphotobacteria (oxygen-releasing photosynthetic forms, such as cyanobacteria)

Type II. Firmicutes (thick-walled Gram-positive bacteria)

Class 1. Firmibacteria (hard cell forms, such as clostridia)

Class 2. Thallobacteria (branched forms, such as actinomycetes)

Type III. Tenericutes (gram-negative bacteria without a cell wall)

Class 1. Mollicutes (soft cell forms such as mycoplasmas)

Type IV. Mendosicutes (bacteria with defective cell wall)

Class 1. Archaebacteria (ancient forms, such as methane-producing)

Domains.

Recent biochemical studies have shown that all prokaryotes are clearly divided into two categories: a small group of archaebacteria (Archaebacteria - "ancient bacteria") and all the rest, called eubacteria (Eubacteria - "true bacteria"). It is believed that archaebacteria are more primitive than eubacteria and closer to the common ancestor of prokaryotes and eukaryotes. They differ from other bacteria in several significant ways, including the composition of the ribosomal RNA (pRNA) molecules involved in protein synthesis, the chemical structure of lipids (fat-like substances), and the presence of some other substances in the cell wall instead of the protein-carbohydrate polymer murein.

In the above classification system, archaebacteria are considered to be just one of the types of the same kingdom that includes all eubacteria. However, according to some biologists, the differences between archaebacteria and eubacteria are so profound that it is more correct to consider the archaebacteria in Monera as a separate sub-kingdom. Recently, an even more radical proposal has emerged. Molecular analysis has revealed such significant differences in the structure of genes between these two groups of prokaryotes that some consider their presence within the same kingdom of organisms illogical. In this regard, it was proposed to create a taxonomic category (taxon) of an even higher rank, calling it a domain, and to divide all living things into three domains - Eucarya (eukaryotes), Archaea (archaebacteria) and Bacteria (current eubacteria).

ECOLOGY

The two most important ecological functions of bacteria are nitrogen fixation and mineralization of organic residues.

Nitrogen fixation.

The binding of molecular nitrogen (N 2) with the formation of ammonia (NH 3) is called nitrogen fixation, and the oxidation of the latter to nitrite (NO - 2) and nitrate (NO - 3) is called nitrification. These are vital processes for the biosphere, since plants need nitrogen, but they can only assimilate its bound forms. At present, approximately 90% (about 90 million tons) of the annual amount of such "fixed" nitrogen is provided by bacteria. The rest is produced by chemical plants or occurs during lightning discharges. Nitrogen in the air, which is approx. 80% of the atmosphere, bound mainly by the Gram-negative genus Rhizobium ( Rhizobium) and cyanobacteria. Rhizobium species symbiose with approximately 14,000 species of leguminous plants (family Leguminosae), which include, for example, clover, alfalfa, soybeans and peas. These bacteria live in the so-called. nodules - swellings that form on the roots in their presence. Bacteria receive organic matter (nutrition) from the plant, and in return supply the host with bound nitrogen. For a year, up to 225 kg of nitrogen per hectare is fixed in this way. Non-legume plants, such as alder, also enter into symbiosis with other nitrogen-fixing bacteria.

Cyanobacteria photosynthesize like green plants, releasing oxygen. Many of them are also capable of fixing atmospheric nitrogen, which is then taken up by plants and eventually by animals. These prokaryotes serve as an important source of fixed nitrogen in the soil in general and rice fields in the East in particular, as well as its main supplier for ocean ecosystems.

Mineralization.

This is the name of the decomposition of organic residues to carbon dioxide (CO 2), water (H 2 O) and mineral salts. From a chemical point of view, this process is equivalent to combustion, so it requires a large amount of oxygen. The upper soil layer contains from 100,000 to 1 billion bacteria per 1 g, i.e. about 2 tons per hectare. Usually, all organic residues, once in the ground, are quickly oxidized by bacteria and fungi. More resistant to decomposition is a brownish organic substance called humic acid, which is formed mainly from lignin contained in wood. It accumulates in the soil and improves its properties.

BACTERIA AND INDUSTRY

Considering the variety of chemical reactions catalyzed by bacteria, it is not surprising that they are widely used in production, in some cases since ancient times. Prokaryotes share the glory of such microscopic human helpers with fungi, primarily yeast, which provide most of the processes of alcoholic fermentation, for example, in the manufacture of wine and beer. Now that it has become possible to introduce useful genes into bacteria, causing them to synthesize valuable substances, such as insulin, the industrial use of these living laboratories has received a powerful new impetus.

Food industry.

Currently, bacteria are used by this industry mainly for the production of cheeses, other fermented milk products and vinegar. The main chemical reactions here are the formation of acids. So, when receiving vinegar, bacteria of the genus Acetobacter oxidize the ethyl alcohol contained in cider or other liquids to acetic acid. Similar processes occur during sauerkraut: anaerobic bacteria ferment sugar contained in the leaves of this plant to lactic acid, as well as acetic acid and various alcohols.

Leaching of ores.

Bacteria are used to leach poor ores, i.e. transferring from them into a solution of salts of valuable metals, primarily copper (Cu) and uranium (U). An example is the processing of chalcopyrite, or copper pyrites (CuFeS 2). Heaps of this ore are periodically watered with water containing chemolithotrophic bacteria of the genus Thiobacillus. In the course of their life, they oxidize sulfur (S), forming soluble sulfates of copper and iron: CuFeS 2 + 4O 2 ® CuSO 4 + FeSO 4. Such technologies greatly simplify the production of valuable metals from ores; in principle, they are equivalent to the processes occurring in nature during the weathering of rocks.

Waste recycling.

Bacteria also serve to convert waste, such as sewage, into less dangerous or even useful products. Waste water is one of the acute problems of modern mankind. Their complete mineralization requires huge amounts of oxygen, and in ordinary reservoirs, where it is customary to dump these wastes, it is no longer enough to “neutralize” them. The solution lies in additional aeration of wastewater in special pools (aerotanks): as a result, mineralizing bacteria have enough oxygen to completely decompose organic matter, and drinking water becomes one of the end products of the process in the most favorable cases. The insoluble precipitate remaining along the way can be subjected to anaerobic fermentation. In order for such water treatment plants to take up as little space and money as possible, a good knowledge of bacteriology is necessary.

Other uses.

Other important areas of industrial application of bacteria include, for example, flax lobe, i.e. separation of its spinning fibers from other parts of the plant, as well as the production of antibiotics, in particular streptomycin (bacteria of the genus Streptomyces).

BACTERIA CONTROL IN INDUSTRY

Bacteria are not only beneficial; the fight against their mass reproduction, for example, in food products or in the water systems of pulp and paper mills, has become a whole area of ​​activity.

Food is spoiled by bacteria, fungi, and their own autolysis-causing ("self-digesting") enzymes, unless they are inactivated by heat or other means. Since bacteria are the main cause of spoilage, designing efficient food storage systems requires knowledge of the tolerance limits of these microorganisms.

One of the most common technologies is milk pasteurization, which kills bacteria that cause, for example, tuberculosis and brucellosis. Milk is kept at 61–63°C for 30 minutes or at 72–73°C for only 15 seconds. This does not impair the taste of the product, but inactivates pathogenic bacteria. Wine, beer and fruit juices can also be pasteurized.

The benefits of storing food in the cold have long been known. Low temperatures do not kill bacteria, but they do not allow them to grow and multiply. True, when freezing, for example, to -25 ° C, the number of bacteria decreases after a few months, but a large number of these microorganisms still survive. At temperatures just below zero, bacteria continue to multiply, but very slowly. Their viable cultures can be stored almost indefinitely after lyophilization (freezing-drying) in a medium containing protein, such as blood serum.

Other well-known food preservation methods include drying (drying and smoking), adding large amounts of salt or sugar, which is physiologically equivalent to dehydration, and pickling, i.e. placed in a concentrated acid solution. With an acidity of the medium corresponding to pH 4 and below, the vital activity of bacteria is usually greatly inhibited or stopped.

BACTERIA AND DISEASE

Bacteria were discovered by A. Leeuwenhoek at the end of the 17th century, and for a long time it was believed that they were capable of spontaneous generation in rotting remains. This hindered the understanding of the connection between prokaryotes and the occurrence and spread of diseases, while at the same time preventing the development of adequate therapeutic and preventive measures. L. Pasteur was the first to establish that bacteria come only from other living bacteria and can cause certain diseases. At the end of the 19th century R. Koch and other scientists have significantly improved the methods for identifying these pathogens and described many of their species. To establish that the observed disease is caused by a well-defined bacterium, Koch's postulates are still used (with minor modifications): 1) this pathogen must be present in all patients; 2) it is possible to obtain its pure culture; 3) it should, when inoculated, cause the same disease in a healthy person; 4) it can be detected in a newly ill person. Further progress in this area is associated with the development of immunology, the foundations of which were laid by Pasteur (at first, French scientists did a lot here), and with the discovery of penicillin in 1928 by A. Fleming.

Gram stain.

For the identification of pathogenic bacteria, the staining method developed in 1884 by the Danish bacteriologist H. Gram turned out to be extremely useful. It is based on the resistance of the bacterial cell wall to discoloration after treatment with special dyes. If it does not discolor, the bacterium is called Gram-positive, otherwise Gram-negative. This difference is associated with structural features of the cell wall and some metabolic features of microorganisms. Assigning a pathogenic bacterium to one of these two groups helps doctors prescribe the right antibiotic or other drug. So, the bacteria that cause boils are always gram-positive, and the causative agents of bacillary dysentery are gram-negative.

Types of pathogens.

Bacteria cannot overcome the barrier created by intact skin; they penetrate the body through wounds and thin mucous membranes lining the inside of the oral cavity, digestive tract, respiratory and genitourinary tract, and so on. Therefore, they are transmitted from person to person with contaminated food or drinking water (typhoid fever, brucellosis, cholera, dysentery), with inhaled moisture droplets that get into the air when the patient sneezes, coughs or just talks (diphtheria, pneumonic plague, tuberculosis, streptococcal infections , pneumonia) or by direct contact of the mucous membranes of two people (gonorrhea, syphilis, brucellosis). Once on the mucous membrane, pathogens can affect only it (for example, pathogens of diphtheria in the respiratory tract) or penetrate deeper, like, say, treponema in syphilis.

Symptoms of bacterial infection are often attributed to the action of toxic substances produced by these microorganisms. They are usually divided into two groups. Exotoxins are secreted from the bacterial cell, for example, in diphtheria, tetanus, scarlet fever (cause of a red rash). Interestingly, in many cases, exotoxins are produced only by bacteria that are themselves infected with viruses containing the corresponding genes. Endotoxins are part of the bacterial cell wall and are released only after the death and destruction of the pathogen.

Food poisoning.

anaerobic bacterium Clostridium botulinum, usually found in soil and silt, is the cause of botulism. It produces very heat-resistant spores that can germinate after pasteurization and smoking of foods. In the course of its vital activity, the bacterium forms several closely related toxins, which are among the strongest known poisons. Less than 1/10,000 mg of such a substance can kill a person. This bacterium occasionally infects factory canned food and more often homemade. It is usually impossible to detect its presence in vegetable or meat products by eye. In the United States, several dozen cases of botulism are recorded annually, with a mortality rate of 30-40%. Fortunately, botulinum toxin is a protein, so it can be inactivated by a short boil.

A much more common food poisoning is caused by a toxin produced by certain strains of Staphylococcus aureus ( Staphylococcus aureus). Symptoms - diarrhea and loss of strength; deaths are rare. This toxin is also a protein, but, unfortunately, it is very heat-resistant, so it is difficult to inactivate it by boiling food. If the products are not severely poisoned with it, then in order to prevent the reproduction of staphylococcus, it is recommended to store them before consumption at a temperature either below 4 ° C or above 60 ° C.

Bacteria of the genus Salmonella are also capable of contaminating food, causing harm to health. Strictly speaking, this is not food poisoning, but an intestinal infection (salmonellosis), the symptoms of which usually appear 12–24 hours after the pathogen enters the body. Its mortality rate is quite high.

Staphylococcal poisoning and salmonellosis are mainly associated with the consumption of meat products and salads that have stood at room temperature, especially at picnics and festive feasts.

The body's natural defenses.

In animals, there are several "lines of defense" against pathogens. One of them is formed by white blood cells, phagocytic, i.e. absorbing, bacteria and foreign particles in general, the other is the immune system. Both of them work in conjunction.

The immune system is very complex and exists only in vertebrates. If a foreign protein or high molecular weight carbohydrate penetrates into the blood of an animal, then it becomes an antigen here, i.e. a substance that stimulates the body to produce an "opposing" substance - antibodies. An antibody is a protein that binds, i.e. inactivates its specific antigen, often causing its precipitation (precipitation) and removal from the bloodstream. Each antigen corresponds to a strictly defined antibody.

Bacteria, as a rule, also cause the formation of antibodies that stimulate lysis, i.e. destruction of their cells and make them more accessible for phagocytosis. It is often possible to pre-immunize an individual, increasing their natural resistance to bacterial infection.

In addition to “humoral immunity” provided by antibodies circulating in the blood, there is “cellular” immunity associated with specialized white blood cells, the so-called. T-cells, which kill bacteria through direct contact with them and with the help of toxic substances. T cells are also needed to activate macrophages, another type of white blood cell that also kills bacteria.

Chemotherapy and antibiotics.

At first, very few drugs (chemotherapeutic drugs) were used to fight bacteria. The difficulty was that, although these drugs easily kill germs, often such treatment is harmful to the patient himself. Fortunately, the biochemical similarity between humans and microbes is now known to be incomplete. For example, antibiotics of the penicillin group, synthesized by certain fungi and used by them to fight competing bacteria, disrupt the formation of the bacterial cell wall. Since human cells do not have such a wall, these substances are harmful only to bacteria, although sometimes they cause an allergic reaction in us. In addition, prokaryotic ribosomes, somewhat different from ours (eukaryotic ones), are specifically inactivated by antibiotics such as streptomycin and chloromycetin. Further, some bacteria must provide themselves with one of the vitamins - folic acid, and its synthesis in their cells is suppressed by synthetic sulfa drugs. We ourselves get this vitamin with food, so we do not suffer with such treatment. There are now natural or synthetic drugs against almost all bacterial pathogens.

Healthcare.

The fight against pathogens at the level of the individual patient is only one aspect of the application of medical bacteriology. It is equally important to study the development of bacterial populations outside the patient's body, their ecology, biology and epidemiology, i.e. distribution and population dynamics. It is known, for example, that the causative agent of plague Yersinia pestis lives in the body of rodents that serve as a “natural reservoir” of this infection, and fleas are its carriers between animals. If sewage flows into a reservoir, pathogens of a number of intestinal infections remain viable there for a certain period of time, depending on various conditions. Thus, the alkaline reservoirs of India, where the pH of the environment changes depending on the season, is a very favorable environment for the survival of cholera vibrio ( Vibrio cholerae) ().

Information of this kind is essential for health workers involved in identifying disease outbreaks, interrupting transmission routes, implementing immunization programs and other preventive activities.

STUDY OF BACTERIA

Many bacteria are easy to grow in the so-called. culture medium, which may include meat broth, partially digested protein, salts, dextrose, whole blood, its serum and other components. The concentration of bacteria in such conditions usually reaches about a billion per cubic centimeter, resulting in a cloudy environment.

To study bacteria, it is necessary to be able to obtain their pure cultures, or clones, which are the offspring of a single cell. This is necessary, for example, to determine which type of bacteria infected the patient and to which antibiotic this type is sensitive. Microbiological samples, such as swabs taken from the throat or wounds, samples of blood, water or other materials, are highly diluted and applied to the surface of a semi-solid medium: rounded colonies develop from individual cells on it. The solidifying agent for the culture medium is usually agar, a polysaccharide derived from certain seaweeds and almost indigestible by any type of bacteria. Agar media are used in the form of "jambs", i.e. inclined surfaces formed in test tubes standing at a large angle when the molten culture medium solidifies, or in the form of thin layers in glass Petri dishes - flat round vessels closed with a lid of the same shape, but slightly larger in diameter. Usually, after a day, the bacterial cell has time to multiply so much that it forms a colony that is easily visible to the naked eye. It can be transferred to another environment for further study. All culture media must be sterile before the bacteria are grown, and measures must be taken afterwards to prevent the settlement of undesirable microorganisms on them.

To examine the bacteria grown in this way, a thin wire loop is calcined on a flame, first touching it with a colony or smear, and then with a drop of water deposited on a glass slide. Evenly distributing the taken material in this water, the glass is dried and quickly passed over the burner flame two or three times (the side with the bacteria should be turned up): as a result, the microorganisms, without being damaged, are firmly attached to the substrate. A dye is dripped onto the surface of the preparation, then the glass is washed in water and dried again. The sample can now be viewed under the microscope.

Pure cultures of bacteria are identified mainly by their biochemical characteristics, i.e. determine whether they form gas or acids from certain sugars, whether they are able to digest protein (liquefy gelatin), whether they need oxygen for growth, etc. They also check whether they are stained with specific dyes. Sensitivity to certain drugs, such as antibiotics, can be determined by placing small discs of filter paper soaked with these substances on a surface inoculated with bacteria. If any chemical compound kills bacteria, a zone free from them is formed around the corresponding disk.



Bacterial infections are considered one of the most dangerous - humanity has been fighting pathogenic microorganisms for more than one century. However, not all bacteria are unambiguous enemies for humans. Many species are vital - they ensure proper digestion and even help the immune system defend itself against other microorganisms. MedAboutMe will tell you how to distinguish between bad and good bacteria, what to do if they are found in the analysis, and how to properly treat the diseases they cause.

Bacteria and man

It is believed that bacteria appeared on Earth more than 3.5 billion years ago. It was they who became active participants in creating suitable conditions for life on the planet, and throughout their existence they have been actively involved in important processes. For example, it is thanks to bacteria that the decay of the organic remains of animals and plants occurs. They also created fertile soil on Earth.

And since bacteria live literally everywhere, the human body is no exception. On the skin, mucous membranes, in the gastrointestinal tract, nasopharynx, urogenital tract, there are many microorganisms that interact with humans in different ways.

In the womb, the placenta protects the fetus from the penetration of bacteria, the population of the body occurs in the first days of life:

• The first bacteria the child receives, passing through the birth canal of the mother.
• Microorganisms enter the gastrointestinal tract through breastfeeding. Here, among more than 700 species, lactobacilli and bifidobacteria predominate (the benefits are described in the table of bacteria at the end of the article).
• The oral cavity is inhabited by staphylococci, streptococci and other microbes, which the child also receives with food and in contact with objects.
• On the skin, the microflora is formed from bacteria that predominate in the people around the child.

The role of bacteria for a person is invaluable, if already in the first months the microflora does not form normally, the child will lag behind in development and often get sick. After all, without symbiosis with bacteria, the body cannot function.

Beneficial and harmful bacteria

Everyone is well aware of the concept of dysbacteriosis - a condition in which the natural microflora in the human body is disturbed. Dysbacteriosis is a serious factor in lowering the immune defense, the development of various inflammations, disruption of the digestive tract and other things. The absence of beneficial bacteria contributes to the reproduction of pathogenic organisms, and fungal infections often develop against the background of dysbacteriosis.

At the same time, many pathogenic microbes live in the environment, which can cause serious illness. The most dangerous are those types of bacteria that in the process of life are capable of producing toxins (exotoxins). It is these substances that are today considered one of the most powerful poisons. Such microorganisms cause dangerous infections:

• Botulism.
• Gas gangrene.
• diphtheria.
• Tetanus.

In addition, the disease can be provoked by bacteria that live in the human body under normal conditions, and when the immune system is weakened, they begin to become more active. The most popular pathogens of this kind are staphylococci and streptococci.

Bacteria life

Bacteria are full-fledged living organisms with a size of 0.5-5 microns, which are able to actively multiply in a suitable environment. Some of them need oxygen, others do not. There are motile and non-motile types of bacteria.

Bacteria cell

Most bacteria living on Earth are single-celled organisms. Mandatory components of any microbe:

• Nucleoid (nucleus-like region containing DNA).
• Ribosomes (carry out the synthesis of proteins).
• Cytoplasmic membrane (separates the cell from the external environment, maintains homeostasis).

Also, some bacterial cells have a thick cell wall, which additionally protects them from damage. Such organisms are more resistant to drugs and antigens that the human immune system produces.

There are bacteria with flagella (mototrichia, lophotrichia, peritrichia), due to which microorganisms are able to move. However, scientists have also recorded another type of movement characteristic of microbes - the sliding of bacteria. Moreover, recent studies show that it is inherent in those species that were previously considered immobile. For example, scientists from the University of Nottingham and Sheffield have shown that methicillin-resistant Staphylococcus aureus (one of the main representatives of the class of superbugs) is able to move without the help of flagella and villi. And this, in turn, significantly affects the understanding of the mechanisms of the spread of a dangerous infection.

Bacterial cells can be of the following forms:

• Round (cocci, from other Greek κόκκος - "grain").
• Rod-shaped (bacilli, clostridia).
• Sinuous (spirochetes, spirilla, vibrios).

Many microorganisms are able to stick together in colonies, so more often scientists and doctors isolate bacteria not by the structure of the element, but by the type of compounds:

• Diplococci are cocci connected in pairs.
• Streptococci are cocci that form chains.
• Staphylococci are cocci that form clusters.
• Streptobacteria are rod-shaped microorganisms connected in a chain.

Reproduction of bacteria

The vast majority of bacteria reproduce by division. The rate of spread of the colony depends on the external conditions and the type of microorganism itself. So, on average, one bacterium is able to divide every 20 minutes - it forms 72 generations of offspring per day. For 1-3 days, the number of descendants of one microorganism can reach several million. In this case, the reproduction of bacteria may not be so fast. For example, the process of division of Mycobacterium tuberculosis takes 14 hours.

If the bacteria enter a favorable environment and have no competitors, the population grows very quickly. Otherwise, its number is regulated by other microorganisms. That is why the human microflora is an essential factor in its protection against various infections.

bacterial spores

One of the features of rod-shaped bacteria is their ability to sporulate. These microorganisms are called bacilli, and they include such pathogenic bacteria:

• The genus Clostridium (cause gas gangrene, botulism, often cause complications during childbirth and after abortion).
• The genus Bacillus (cause anthrax, a number of food poisonings).

Bacterial spores are, in fact, a conserved cell of a microorganism that can survive for a long time without damage, and is practically not subject to various influences. In particular, spores are heat-resistant, not damaged by chemicals. Often the only possible effect is ultraviolet rays, under which the dried bacteria can die.

Bacterial spores form when the microorganism is exposed to unfavorable conditions. It takes approximately 18-20 hours to form inside the cell. At this time, the bacterium loses water, decreases in size, becomes lighter, and a dense shell forms under the outer membrane. In this form, the microorganism can freeze for hundreds of years.

When the spore of a bacterium is exposed to suitable conditions, it begins to germinate into a viable bacterium. The process takes about 4-6 hours.

Types of bacteria

According to the influence of bacteria on humans, they can be divided into three types:

• Pathogenic.
• Conditionally pathogenic.
• Non-pathogenic.

Beneficial bacteria

Non-pathogenic bacteria - those that never lead to disease, even if their numbers are large enough. Among the most famous species, lactic acid bacteria can be distinguished, which are actively used by humans in the food industry - for making cheeses, sour-milk products, dough and much more.

Another important species is bifidobacteria, which are the basis of the intestinal flora. In breastfed infants, they make up to 90% of all species living in the gastrointestinal tract. These bacteria for humans perform the following functions:

• Provide physiological protection of the intestine from the penetration of pathogenic organisms.
• They produce organic acids that prevent the reproduction of pathogenic microbes.
• They help to synthesize vitamins (K, group B), as well as proteins.
• Enhance the absorption of vitamin D.

The role of bacteria of this species is difficult to overestimate, because without them normal digestion is impossible, and hence the absorption of nutrients.

Opportunistic bacteria

As part of a healthy microflora, there are bacteria that are classified as opportunistic pathogens. These microorganisms can exist for years on the skin, in the nasopharynx or intestines of a person and not cause infections. However, under any favorable conditions (weakened immunity, microflora disturbances), their colony grows and becomes a real threat.

A classic example of an opportunistic bacterium is Staphylococcus aureus, a microbe that can cause over 100 different diseases, from boils on the skin to deadly blood poisoning (sepsis). At the same time, this bacterium is found in most people in various analyzes, but it still does not cause illness.

Among other representatives of the species of opportunistic microbes:

• Streptococci.
• Escherichia coli.
• Helicobacter pylori (capable of causing ulcers and gastritis, but lives in 90% of people as part of a healthy microflora).

Getting rid of these types of bacteria does not make sense, since they are widespread in the environment. The only adequate way to prevent infections is to strengthen the immune system and protect the body from dysbacteriosis.

Pathogenic bacteria behave differently - their presence in the body always means the development of an infection. Even a small colony can cause harm. Most of these microorganisms secrete two types of toxins:

• Endotoxins are poisons that are formed when cells are destroyed.
• Exotoxins are poisons that bacteria produce during their life. The most dangerous substances for humans that can lead to fatal intoxication.

The treatment of such infections is aimed not only at the destruction of pathogenic bacteria, but also at the removal of the poisoning caused by them. Moreover, in the case of infection with microbes such as tetanus bacillus, it is the introduction of toxoid that is the basis of therapy.

Other known pathogenic bacteria include:

• Salmonella.
• Pseudomonas aeruginosa.
• Gonococcus.
• Pale treponema.
• Shigella.
• Tuberculosis bacillus (Koch's stick).

Classes of bacteria

Today there are many classifications of bacteria. Scientists divide them according to the type of structure, ability to move and other features. However, the Gram classification and the type of breathing remain the most important.

Anaerobic and aerobic bacteria

Among the diversity of bacteria, two large classes are distinguished:

• Anaerobic - those that can do without oxygen.
• Aerobic - those that need oxygen to live.

A feature of anaerobic bacteria is their ability to live in environments where other microorganisms do not survive. The most dangerous in this regard are deep contaminated wounds, in which microbes develop rapidly. The characteristic signs of the growth of the population and life of bacteria in the human body are as follows:

• Progressive tissue necrosis.
• Subcutaneous suppurations.
• Abscesses.
• Internal lesions.

Anaerobes include pathogenic bacteria that cause tetanus, gas gangrene, and toxic lesions of the gastrointestinal tract. Also, the anaerobic class of bacteria includes many opportunistic microbes that live on the skin and in the intestinal tract. They become dangerous if they get into an open wound.

Disease-causing aerobic bacteria include:

• Tuberculosis bacillus.
• Vibrio cholerae.
• Tularemia stick.

The life of bacteria can proceed even with a small amount of oxygen. Such microbes are called facultative aerobic, salmonella and cocci (streptococcus, staphylococcus) are a striking example of the group.

In 1884, Danish physician Hans Gram discovered that different bacteria stained differently when exposed to methylene violet. Some retain color after washing, others lose it. Based on this, the following classes of bacteria were isolated:

• Gram-negative (Gram-) - discoloring.
• Gram-positive (Gram +) - staining.

Staining with aniline dyes is a simple technique that makes it possible to quickly reveal the characteristics of the bacterial membrane wall. For those microbes that do not stain by Gram, it is more powerful and durable, which means that it is more difficult to deal with them. Gram-negative bacteria are primarily more resistant to antibodies produced by the human immune system. This class includes microbes that cause such diseases:

• Syphilis.
• Leptospirosis.
• Chlamydia.
• meningococcal infection.
• Hemophilus infection
• Brucellosis.
• Legionellosis.

The Gram+ class of bacteria includes the following microorganisms:

• Staphylococcus.
• Streptococcus.
• Clostridia (causative agents of botulism and tetanus).
• Listeria.
• Diphtheria stick.

Diagnosis of bacterial infections

Correct and timely diagnosis plays an important role in the treatment of bacterial infections. It is possible to accurately determine the disease only after the analysis, but it can already be suspected by the characteristic symptoms.

Bacteria and viruses: features of bacteria and differences in infections

Most often, a person is faced with acute respiratory diseases. As a rule, cough, rhinitis, fever and sore throat are caused by bacteria and viruses. And although at certain stages of the disease they can manifest themselves in the same way, their therapy will still be radically different.

Bacteria and viruses behave differently in the human body:

• Bacteria are full-fledged living organisms, large enough (up to 5 microns), capable of reproduction in a suitable environment (on mucous membranes, skin, in wounds). Pathogenic microbes secrete poisons that lead to intoxication. The same bacteria can cause infections of different localization. For example, Staphylococcus aureus affects the skin, mucous membranes, and can lead to blood poisoning.
• Viruses are non-cellular infectious agents that can reproduce only inside a living cell, and in the external environment do not manifest themselves as living organisms. At the same time, viruses are always highly specialized and can only infect a specific type of cell. For example, hepatitis viruses can only infect the liver. Viruses are much smaller than bacteria, their size does not exceed 300 nm.

Today, effective drugs have been developed against bacteria -. But these drugs do not act on viruses, moreover, according to the World Health Organization, antibacterial therapy for ARVI worsens the patient's condition.

Symptoms of bacterial infections

Most often, seasonal respiratory infections develop under the influence of bacteria and viruses according to the following scheme:

• The first 4-5 days manifest a viral infection.
• On the 4-5th day, if the rules for the treatment of acute respiratory viral infections were not followed, a bacterial lesion joins.

Symptoms of a bacterial infection in this case will be:

• Deterioration of the patient's condition after improvement.
• High temperature (38°C and above).
• Severe pain in the chest (a sign of the development of pneumonia).
• Discoloration of mucus - greenish, white or yellowish discharge from the nose and in expectorated sputum.
• Rash on the skin.

If it is possible to treat without the involvement of a doctor, since a viral infection resolves itself without complications in 4-7 days, then diseases caused by pathogenic bacteria must be consulted by a therapist or pediatrician.

Other bacterial infections are characterized by the following symptoms:

• General deterioration.
• A pronounced inflammatory process - pain in the affected area, hyperemia, fever.
• Suppuration.

Methods of transmission of bacterial infections

Harmful bacteria enter the human body in many ways. The most common ways of infection:

• Airborne.

Bacteria are found in the exhaled air, sputum of the patient, spread by coughing, sneezing and even talking. This route of transmission is typical for respiratory infections, in particular, whooping cough, diphtheria, scarlet fever.

• Contact household.

Microbes get to a person through dishes, door handles, furniture surfaces, towels, phones, toys and more. Also, live bacteria and bacterial spores can stay in the dust for a long time. This is how tuberculosis, diphtheria, dysentery, diseases caused by aureus and other types of staphylococcus aureus are transmitted.

• Alimentary (fecal-oral).

Bacteria enter the body through contaminated food or water. The transmission route is characteristic of gastrointestinal infections, in particular, typhoid fever, cholera, dysentery.

• Sexual.

Infection occurs during sexual intercourse, this is how STIs are transmitted, including syphilis and gonorrhea.

• Vertical.

The bacterium enters the fetus during pregnancy or childbirth. So the child can become infected with tuberculosis, syphilis, leptospirosis.

Deep wounds are dangerous for the development of infections - it is here that anaerobic bacteria, including tetanus bacillus, actively multiply. People with weakened immune systems are also more likely to contract a bacterial infection.

If you suspect the presence of pathogenic bacteria, the doctor may offer the following diagnostic options:

• Smear on flora.

If a respiratory infection is suspected, it is taken from the mucous membranes of the nose and throat. The analysis is also popular for detecting sexually transmitted infections. In this case, the material is taken from the vagina, visceral canal, urethra.

• Bacteriological culture.

It differs from a smear in that the taken biomaterial is not examined immediately, but is placed in an environment favorable for the reproduction of bacteria. After a few days or weeks, depending on the alleged pathogen, the result is evaluated - if there were harmful bacteria in the biomaterial, they grow into a colony. Bakposev is also good in that during the analysis, not only the pathogen is determined, but also its quantity, as well as the sensitivity of the microbe to antibiotics.

• Blood test.

A bacterial infection can be detected by the presence of antibodies, antigens in the blood and by the leukocyte formula.

Today, biomaterial is often examined by PCR (polymerase chain reaction), in which infection can be detected even with a small number of microbes.

Positive test and bacterial infections

Since many bacteria are opportunistic and at the same time live in the body, on the mucous membranes and skin of the majority of the population, the results of the analysis must be able to correctly interpret. It must be remembered that the mere presence of bacteria in a person is not a sign of a bacterial infection and is not a reason to start treatment. For example, the norm for Staphylococcus aureus is 103–104. With these indicators, no therapy is required. Moreover, since the microflora of each person is individual, even if the values ​​\u200b\u200bare higher, but there will be no symptoms of the disease, the indicators can also be considered normal.

An analysis for different types of bacteria is prescribed if there are signs of infection:

• Feeling unwell.
• Purulent discharge.
• Inflammatory process.
• Greenish, white or yellow mucus from the nose and in the expectorated sputum.

A positive analysis for bacteria in the absence of symptoms is taken for control if microbes are detected in people from risk groups: pregnant women, children, people in the postoperative period, patients with reduced immunity and concomitant diseases. In this case, it is recommended to take several tests to see the growth dynamics of the colony. If the values ​​do not change, then the immune system is able to control the reproduction of bacteria.

Bacteria in the nasopharynx

Bacteria in the nasopharynx can cause respiratory tract infections. In particular, they are the cause of tonsillitis, bacterial tonsillitis and pharyngitis, as well as sinusitis. Running infections can cause a lot of inconvenience, chronic inflammation, persistent rhinitis, headaches and more. Such diseases are especially dangerous because harmful bacteria can descend through the respiratory tract and affect the lungs - causing pneumonia.

bacteria in urine

Ideally, it is urine that should be free from various microorganisms. The presence of bacteria in the urine may indicate an incorrectly passed analysis (in which microbes got into the material from the surface of the skin and mucous membranes), in which case the doctor asks to be examined again. If the result is confirmed, and the indicator exceeds 104 CFU / ml, bacteriuria (bacteria in the urine) indicates such diseases:

• Kidney damage, in particular, pyelonephritis.
• Cystitis.
• Urethritis.
• Inflammatory process in the urinary canal, for example, as a result of blocking it with a calculus. Observed in urolithiasis.
• Prostatitis or prostate adenoma.

In some cases, bacteria in the urine are found in diseases that are not associated with a local infection. A positive analysis can be with diabetes mellitus, as well as a generalized lesion - sepsis.

Normally, the gastrointestinal tract is inhabited by colonies of various bacteria. In particular, there are:

• Bifidobacteria.
• Lactic acid bacteria (lactobacilli).
• Enterococci.
• Clostridia.
• Streptococci.
• Staphylococci.
• Escherichia coli.

The role of the bacteria that make up the normal microflora is to protect the intestines from infections and ensure normal digestion. Therefore, often the biomaterial from the intestine is examined precisely because of the suspicion of dysbacteriosis, and not for the presence of pathogenic microorganisms.

However, some pathogenic bacteria can cause severe diseases, namely when they enter the gastrointestinal tract. Among these diseases:

• Salmonellosis.
• Cholera.
• Botulism.
• Dysentery.

bacteria on the skin

On the skin, as well as on the mucous membranes of the nasopharynx, in the intestines and genital organs, the balance of microflora is normally established. Bacteria live here - more than 100 species, among which epidermal and Staphylococcus aureus, streptococci are often found. With reduced immunity, and especially in children, they can provoke skin lesions, cause suppuration, boils and carbuncles, streptoderma, panaritium and other diseases.

In adolescence, the active reproduction of bacteria leads to acne and acne.

The main danger of microbes on the skin is the possibility of their entry into the bloodstream, wounds and other damage to the epidermis. In this case, harmless microorganisms on the skin can cause serious illness, even cause sepsis.

Diseases caused by bacteria

Bacteria are the cause of infections throughout the body. They affect the respiratory tract, cause inflammatory processes on the skin, cause diseases of the intestines and the genitourinary system.

Diseases of the respiratory tract and lungs

Angina

Angina is an acute lesion of the tonsils. The disease is typical for childhood.

Pathogen:

• Streptococci, rarely staphylococci and other forms of bacteria.

Typical symptoms:

• inflammation of the tonsils with a whitish coating on them, pain when swallowing, hoarseness, high fever, no rhinitis.

Disease risk:

• if a sore throat is not treated well enough, rheumatoid heart disease can become a complication - harmful bacteria spread through the blood and lead to heart valve defects. As a result, heart failure may develop.

Whooping cough is a dangerous infectious disease that mainly affects children. Highly contagious, the bacterium is transmitted by airborne droplets, therefore, without a sufficient level of immunization of the population, epidemics are easily caused.

Pathogen:

• Bordetella pertussis.

Typical symptoms:

• the disease at first proceeds like a common cold, later a characteristic paroxysmal barking cough appears, which may not go away for 2 months, after an attack the child may vomit.

Disease risk:

• Whooping cough is most dangerous for children of the first year of life, as it can cause respiratory arrest and death. Typical complications are pneumonia, bronchitis, false croup. From severe coughing attacks, it is extremely rare for a cerebral hemorrhage or pneumothorax to occur.

Pneumonia

Inflammation of the lungs can be caused by bacteria and viruses, as well as some fungi. Bacterial pneumonia, the most common complication of viral respiratory infections, can develop after the flu. Also, the multiplication of bacteria in the lungs is typical for bedridden patients, the elderly, patients with chronic lung diseases and respiratory disorders, with dehydration.

Pathogen:

• Staphylococci, pneumococci, Pseudomonas aeruginosa and others.

Typical symptoms:

• severe fever (up to 39 ° C and above), cough with copious moist greenish or yellowish sputum, chest pain, shortness of breath, feeling short of breath.

Disease risk:

• depends on the pathogen. With insufficient treatment, respiratory arrest and death are possible.

Tuberculosis

Tuberculosis is one of the most dangerous lung diseases that is difficult to treat. In Russia, tuberculosis has been a socially significant disease since 2004, since the number of infected people is much higher than in developed countries. Back in 2013, up to 54 cases of infection per 100,000 people were recorded.

Pathogen:

• mycobacterium, Koch's bacillus.

Typical symptoms:

• the disease may not manifest itself for a long time, then a cough occurs, a general malaise, a person loses weight, a subfebrile temperature (37-38 ° C) is observed for a month or more, a painful blush. Later, hemoptysis and severe pain appear.

Disease risk:

• features of the bacteria that cause tuberculosis is the development of resistance to antibiotics. Therefore, the infection is difficult to treat and can lead to death or disability. Common complications are heart disease.

Diphtheria is an infectious disease that in 90% of cases affects the upper respiratory tract. Diphtheria is especially dangerous for young children.

Pathogen:

• Corynebacterium diphtheriae (Leffler's bacillus).

Typical symptoms:

• pain when swallowing, hyperemia of the tonsils and specific white films on them, swollen lymph nodes, shortness of breath, high fever, general intoxication of the body.

Disease risk:

• Without timely treatment, diphtheria is fatal. The bacterial cell is capable of producing exotoxin, so the sick person can die from poisoning, in which the heart and nervous system are affected.

Intestinal infections

salmonellosis

Salmonellosis is one of the most common intestinal infections that can occur in different forms. Sometimes bacteria cause severe lesions, but there are times when the disease is mild or no symptoms at all.

Pathogen:

• Salmonella.

Typical symptoms:

• high temperature (up to 38-39 ° C), chills, abdominal pain, vomiting, diarrhea, severe intoxication of the body, in which a person sharply weakens.

Disease risk:

• Depending on the form of the course, in severe infections, bacterial toxins can lead to kidney failure or peritonitis. Children are at risk of dehydration.

Dysentery

Dysentery is an intestinal infection that affects people of all ages. Most often recorded in the summer hot period.

Pathogen:

• 4 types of Shigella bacteria.

Typical symptoms:

• Loose stools of dark green color with impurities of blood and pus, nausea, headaches, loss of appetite.

Disease risk:

• dehydration, which leads to the attachment of various inflammations, as well as intoxication of the body. With proper treatment, good immunity and sufficient fluid intake, the life of Shigella bacteria stops in 7-10 days. Otherwise, a serious complication is possible - intestinal perforation.

Gonorrhea

Gonorrhea is transmitted exclusively through sexual contact, but in rare cases, the infection can be passed from mother to child during childbirth (the baby develops conjunctivitis). The bacteria that causes gonorrhea can grow in the anus or throat, but it most often affects the genitals.

Pathogen:

• Gonococcus.

Typical symptoms:

• possible asymptomatic course of the disease: in men in 20%, in women - more than 50%. In the acute form, there are pains during urination, white-yellow discharge from the penis and vagina, burning and itching.

Disease risk:

• If left untreated, the infection can cause infertility and can also damage the skin, joints, cardiovascular system, liver, and brain.

Syphilis

Syphilis is characterized by slow progression, symptoms appear gradually and do not develop quickly. The characteristic course of the disease is an alternation of exacerbations and remissions. Household infection, many doctors question, in the vast majority of cases, bacteria are transmitted to humans sexually.

Pathogen:

• Pale treponema.

Typical symptoms:

• at the first stage, an ulcer appears on the genitals, which heals on its own in 1-1.5 months, an increase in lymph nodes is observed. After, after 1-3 months, a pale rash appears all over the body, the patient feels weak, the temperature may rise, the symptoms resemble the flu.

Disease risk:

• pathogenic bacteria eventually lead to the development of tertiary syphilis (30% of all infected), which affects the aorta, brain and back, brain, bones and muscles. Perhaps the development of damage to the nervous system - neurosyphilis.

Chlamydia

Chlamydia is a sexually transmitted infection that is often asymptomatic. In addition, pathogenic bacteria are difficult to detect; PCR analysis is prescribed for diagnosis.

Pathogen:

• Chlamydia.

Typical symptoms:

• in the acute form, discharge from the genital organs (usually transparent), pain during urination, blood discharge are observed.

Disease risk:

• in men - inflammation of the epididymis, in women - inflammation of the uterus and appendages, infertility, Reiter's syndrome (inflammation of the urethra).

Meningococcal infection

Meningococcal infection is a group of diseases caused by one pathogen, but occurring in different forms. A person may be an asymptomatic carrier of the bacterium, and in other cases, the microbe causes a generalized infection leading to death.

Pathogen:

• Meningococcus.

Typical symptoms:

• vary with the severity of the disease. The infection can manifest itself as a mild cold, in severe cases, meningococcemia develops, characterized by an acute onset of the disease, the appearance of a red rash (does not disappear with pressure), the temperature rises, confusion is observed.

Disease risk:

• in severe form, tissue necrosis develops, gangrene of the fingers and extremities, and brain damage are possible. With the development of infectious-toxic shock, death quickly occurs.

Tetanus

Tetanus is a dangerous infection that develops in wounds on the skin. The causative agent forms spores of bacteria, in the form of which it is found in the external environment. When it enters the wound, it quickly germinates. Therefore, any serious injury requires the prevention of infection - the introduction of tetanus toxoid.

Pathogen:

• Tetanus stick.

Typical symptoms:

• tetanus affects the central nervous system, at first it is manifested by tonic tension of the jaw muscles (it is difficult for a person to speak, open his mouth), later it spreads to the whole body, the patient arches due to muscle hypertonicity, and at the end respiratory failure develops.

Disease risk:

• the main danger is the toxin that the bacterium secretes, it is he who leads to severe symptoms. As a result of poisoning, tonic tension of all muscles occurs, including the diaphragm and intercostal muscles, as a result of which a person cannot breathe and dies from hypoxia.

Treatment of bacterial diseases

Any bacterial infection needs planned treatment, because bacteria can cause serious damage to the body. Only the doctor chooses the appropriate treatment regimen, which depends not only on the type of disease, but also on the severity of the course.

Antibiotics

Antibiotics are considered the mainstay of treatment for all infections caused by harmful bacteria. Since the discovery of penicillin in the 1920s, many diseases have been moved from fatal to curable. The number of complications after operations has decreased, and, from which every fourth person died, remained a dangerous disease only for people from risk groups.

Modern antibiotics can be divided into two groups:

• Bactericidal - kill pathogenic bacteria.
• Bacteriostatic - slow down the growth, stop the reproduction of bacteria.

The former have a more pronounced effect, however, it is the drugs from the second group that are prescribed more often, since, as a rule, they cause fewer complications.

It is also customary to divide drugs according to the spectrum of action:

• Broad-spectrum antibiotics (penicillins, tetracyclines, macrolides) are used to kill different types of bacteria. They are effective in the case when treatment needs to be started urgently, even before the tests. Penicillins are most commonly prescribed for respiratory bacterial infections.
• Antibiotics that are active against a limited number of bacterial species (often prescribed for tuberculosis and other specific infections).

Any antibiotics must be taken in a course, because if treatment is interrupted, the remaining living bacteria quickly restore the colony.

Problems in the use of antibiotics

Despite the widespread use of antibiotics, doctors today are looking for alternative drugs to treat bacterial infections. This is due to several significant disadvantages of these drugs:

• Development of resistance in bacteria.

Many microorganisms have developed defense mechanisms against drugs, and the use of classical antibiotics is no longer effective. For example, first-generation penicillins, which actively fought against staphylococci and streptococci, are not used today. Staphylococcus aureus has learned to synthesize the enzyme penicillinase, which destroys the antibiotic. Of particular danger are new strains of bacteria that have developed resistance to the latest generation of drugs - the so-called superbugs. The most famous of these is methicillin-resistant Staphylococcus aureus. Also, Pseudomonas aeruginosa and enterococci quickly develop resistance.

• The use of broad-spectrum antibiotics leads to dysbacteriosis.

After such treatment, the balance of microflora is significantly disturbed, complications often develop, the body is weakened not only by the disease, but also by the action of drugs. The use of medicines is limited among certain population groups: pregnant women, children, patients with liver and kidney damage, and other categories.

bacteriophages

An alternative to antibiotics could be bacteriophages, viruses that kill a specific class of bacteria. Among the advantages of such drugs:

• Low likelihood of developing resistance, since bacteriophages are organisms that have lived on Earth for several billion years and continue to infect bacterial cells.
• They do not violate the microflora, since they are specialized medicines - effective only in relation to a specific type of microorganisms.
• Can be used by people at risk.

Preparations containing bacteriophages are already available in pharmacies today. But still, such therapy is losing to antibiotics. Many diseases require immediate treatment, which means that broad-spectrum drugs are needed, while bacteriophages are highly specialized - they can be prescribed only after the pathogen has been identified. In addition, currently known viruses are not able to destroy such a large list of pathogenic bacteria as antibiotics.

Other treatments

WHO does not recommend the use of antibiotics for all types of bacterial infections. In the event that the microbe does not have a high pathogenicity, and the disease proceeds without complications, symptomatic treatment is sufficient - the use of antipyretics, painkillers, vitamin complexes, heavy drinking and other things. Often the immune system itself can suppress the reproduction of a colony of pathogenic microorganisms. However, in this case, the patient must be under the supervision of a doctor who will decide on the appropriateness of a particular method of therapy.

Effective vaccines have been developed for many deadly bacterial infections. Vaccinations are recommended for the following diseases:

• Tuberculosis.
• Haemophilus infection.
• Pneumococcal infection.
• Diphtheria (toxoid is used - a vaccine that helps produce antibodies to the toxin of the bacterium).
• Tetanus (toxoid is used).

Bacteria, nutrition and digestion

The live bacteria in foods alone can restore the gut microflora, help the digestive tract, and get rid of toxins. Others, on the contrary, getting into the digestive tract with food, cause dangerous infections and serious poisoning.

• Pathogenic bacteria often multiply in products with violations of storage rules. And breeding anaerobic bacteria are especially dangerous here, which easily increase their numbers even in goods in sealed packaging and canned food.
• Another way of food contamination is through unwashed hands or equipment (knives, cutting boards, etc.). Therefore, food poisoning is easy to get after street food, which was prepared without observing sanitary standards.
• Insufficient heat treatment or its absence also increases the likelihood of the reproduction of various pathogenic forms of bacteria.

Medicines with live bacteria

Preparations with beneficial live bacteria are often recommended by nutritionists for various disorders of the gastrointestinal tract. They help with bloating, flatulence, heaviness, poor digestion of food, frequent poisoning.

In the event that dysbacteriosis is severe, the doctor may recommend a course of drugs to restore microflora.

• Probiotics are products that contain live beneficial bacteria.

The drug is available in capsules with a shell that protects the colonies of microorganisms and helps to deliver them to the intestines in a living form.

• Prebiotics are carbohydrate preparations that contain nutrients for beneficial bacteria.

Such drugs are prescribed if the intestines are inhabited by bifidus and lactobacilli, but their colonies are not large enough.

Lactic acid bacteria are an extensive group of microorganisms that are able to process glucose with the release of lactic acid. In fact, this means that it is precisely these microbes that are involved in the process of fermenting milk - with their help, all fermented milk products are created. Food does not spoil longer precisely thanks to lactic acid bacteria - the acidic environment that they create prevents the growth of pathogens. They exhibit the same protective functions in the human intestine.

The main products in which lactic acid bacteria are present:

• Yogurt without additives.
• Starter cultures, kefir and other fermented milk drinks.
• acidophilus milk.
• Hard cheeses.
• Sauerkraut.

Tables of the main bacteria

Pathogenic bacteria

Bacteria in the table are presented by the main types of microbes that can cause disease. However, many of them also include non-pathogenic or opportunistic bacteria.

Name	bacteria	Type of breath		Diseases caused by bacteria
Staphylococci		Facultative anaerobes		Staphylococcus aureus provokes most purulent diseases. Including: skin lesions, pneumonia, sepsis. Staphylococcus epidermidis causes purulent complications in the postoperative period, and saprophytic - cystitis and urethritis (bacteria are found in the urine).
streptococci		Facultative anaerobes		Scarlet fever, rheumatism (acute rheumatic fever), tonsillitis, pharyngitis, pneumonia, endocarditis, meningitis, abscess.
Clostridia		anaerobic bacteria		Bacteria can be part of a healthy microflora. At the same time, some species are able to secrete the strongest known poison - exotoxin botulinum toxin. Clostridia are the causative agents of tetanus, gas gangrene, and botulism.
		Aerobes, facultative anaerobes		Certain types of bacteria cause anthrax and intestinal infections. The genus also includes Escherichia coli - a representative of healthy microflora.
Enterococci		Facultative anaerobes		Urinary tract infections, endocarditis, meningitis, sepsis.

Beneficial bacteria

The table of bacteria represents the types of microbes that are vital to humans.

Name	bacteria shape	Type of breath	Benefits for the body
bifidobacteria		Anaerobes	Human bacteria, which are part of the intestinal and vaginal microflora, help normalize digestion (drugs with bifidobacteria are prescribed for diarrhea), assimilate vitamins. The peculiarity of bacteria is that they prevent the reproduction of staphylococci, shigella, candida fungus.
	Cocci, sticks	Aerobes requiring reduced oxygen concentration (microaerophilic bacteria)	A group of bacteria that is united by one characteristic - the ability to cause lactic acid fermentation. Used in the food industry, are part of probiotics.
Streptomycetes	Bacteria can form filaments similar to mushroom mycelium		Microorganisms live in soil and sea water. Bacteria play an important role in pharmacology. Used by humans for the production of antibiotics: streptomycin, erythromycin, tetracycline, vancomycin. In particular, streptomycin has long been the main anti-tuberculosis drug. Also used for the production of antifungal (nystatin) and anticancer (daunorubicin) drugs.

The site provides reference information for informational purposes only. Diagnosis and treatment of diseases should be carried out under the supervision of a specialist. All drugs have contraindications. Expert advice is required!

bacteria surround us everywhere. Many of them are very necessary and useful for a person, and many, on the contrary, cause terrible diseases.
Do you know what forms bacteria come in? And how do they reproduce? And what do they eat? Do you want to know?
.site) will help you find in this article.

Shapes and sizes of bacteria

Most bacteria are unicellular organisms. They differ in a wide variety of forms. Bacteria are given names based on their shape. For example, round-shaped bacteria are called cocci (all known streptococci and staphylococci), rod-shaped bacteria are called bacilli, pseudomonads or clostridia (the famous bacteria of this shape include the famous tuberculosis bacillus or Koch's wand). Bacteria can be shaped like spirals, then their names spirochetes, vibrils or spirilla. Not so often, but there are bacteria in the form of stars, different polygons or other geometric shapes.

Bacteria are not at all large, ranging in size from half to five micrometers. The largest bacterium has a size of seven hundred and fifty micrometers. After the discovery of nanobacteria, it turned out that their size is much smaller than previously imagined by scientists. However, to date, nanobacteria have not been well studied. Some scientists even doubt their existence.

Aggregates and multicellular organisms

Bacteria can attach to each other with the help of mucus, forming cell aggregates. At the same time, each individual bacterium is a self-sufficient organism, the vital activity of which does not depend in any way on relatives glued to it. Sometimes it happens that bacteria stick together in order to carry out some common function. Some bacteria, as a rule, of a filamentous form, can also form multicellular organisms.

How do they move?

There are bacteria that themselves are not able to move, but there are also those that are equipped with special devices for movement. Some bacteria move with the help of flagella, while others can glide. How bacteria glide is not yet fully understood. It is believed that bacteria secrete a special mucus that facilitates sliding. And then there are bacteria that can "dive". In order to descend into the depth of any liquid medium, such a microorganism can change its density. In order for a bacterium to start moving in any direction, it must be irritated.

Nutrition

There are bacteria that can only feed on organic compounds, and there are those that can process inorganics into organics and only then use them for their own needs. Bacteria obtain energy in three ways: using respiration, fermentation or photosynthesis.

reproduction

Regarding the reproduction of bacteria, we can say that it also does not differ in uniformity. There are bacteria that do not divide into sexes and multiply by simple division or budding. Some cyanobacteria have the ability to multiple division, that is, at one time they can produce up to a thousand "newborn" bacteria. There are also bacteria that reproduce sexually. Of course, they all do it in a very primitive way. But at the same time, two bacteria transfer their genetic data to the new cell - this is the main feature of sexual reproduction.

Bacteria, of course, deserve your attention, not only because they cause a lot of diseases. These microorganisms were the first living things to inhabit our planet. The history of bacteria on Earth goes back nearly four billion years! Cyanobacteria are the most ancient of the existing ones today, they appeared three and a half billion years ago.

You can experience the beneficial properties of bacteria thanks to the specialists of Tianshi Corporation, who have developed for you

Municipal state educational institution

Kashirinskaya secondary school named after I. Belousova D.A.

Research work on the topic:

Bacteria found on the human skin and their effect on the human body.

biology teacher Zakharova Ekaterina Alekseevna

Kashirino 2018

Introduction

Chapter 1

Chapter 2. Microflora of human skin

Chapter 3 Research methodology (practical part)

Conclusion

Bibliography

Appendix

Introduction

Bacteria are unicellular organisms consisting of one cell.

Bacteria are found everywhere, inhabiting all habitats. The greatest number of them is found in the soil at a depth of up to 3 km. Bacteria are found in fresh and salt water, on glaciers and in hot springs. There are many of them in the air, in the organisms of animals and plants (both living and dead). The human body is no exception. Moreover, 20% of bacteria are in the oral cavity, 20% - on the skin, 15% - in the throat, 15% - in the genitals, 30% - in the gastrointestinal tract. I was always interested to know if bacteria can be found on human skin and what kind of bacteria live there?

Objective : examine the skin of the hands of boys and girls, find and study the bacteria that live on human skin, compare the results and draw conclusions.

Research tasks:

Detect bacteria on the skin of boys and girls;

To form a general idea of ​​\u200b\u200bbacteria living on the skin;

Reveal their effect on the body;

Specify the causes of the appearance of bacteria and use the resulting

data in the biology lesson in grades 5 and 8;

Explain methods of prevention against bacteria.

Relevance: The chosen topic is relevant, since much attention is currently paid to the study of bacteria and their impact on humans.

Hypothesis: I want to suggest that the amount of bacteria on a person's skin directly depends on what kind of lifestyle he leads and how he observes the rules of personal hygiene.

Chapter 1

The air always contains one or another number of microorganisms. They spread through the air. Airborne spread of pathogenic microbes that cause diseases of plants, animals and humans.

The number of microorganisms in 1 cubic meter of air in different places can reach the following sizes: in a barnyard up to 2 million; in residential premises - 20 thousand; on the streets of cities - 5 thousand; in parks - 200; in sea air - 1-2.

bacteria - this is the kingdom of non-nuclear microorganisms, they do not have a clear nuclear membrane. The bacterial cell is surrounded by a dense shell, thanks to which they retain a constant shape. About ten thousand species of bacteria have been described so far. There are three types of bacteria: pathogenic and non-pathogenic.

Pathogenic bacteria are bacteria that cause disease in humans, animals and plants. Many pathogenic bacteria accumulate in the body in the form of biofilms.

cocci are spherical bacteria. Distributed very widely. Depending on the location of the cells in relation to each other, groups are distinguished: micrococci, streptococci, sarcins, tetracocci, diplococci, staphylococci. Dispute does not form. Most cocci living in soil, water, air are inert under normal conditions. Pathogenic species cause inflammation and purulent diseases.

bacilli - a genus of gram-positive rod-shaped bacteria that form intracellular spores. Most bacilli are saprophytes. Some bacilli cause disease in animals and humans.

Spirilla - a genus of gram-negative bacteria that have the form of spirally twisted rods. Mobile. Dispute does not form. Some are pathogenic. They usually live in salt and fresh waters.

Vibrios - the genus is gram-negative, curved in the form of a comma stick, capable of rapid oscillatory movements (hence the name). They live in water bodies, soil, intestinal contents. Vibrio pathogens cause cholera in humans and vibriosis in animals.

Non-pathogenic bacteria - These are bacteria of the normal microflora of the body that do not cause the development of diseases, but often help the body (lactobacilli, bifidumbacteria, enterococci, E. coli, etc.). For example, individual non-pathogenic bacteria living on the human skin and intestines benefit the animal body, as they are able to displace any infection from the surface area they occupy. Biological products from live non-pathogenic bacteria (eubiotics) are used for the prevention and treatment of dysbacteriosis. However, under certain conditions, some bacteria that are considered non-pathogenic can become pathogenic.

Bacteria sizes

The size of bacteria averages 0.5-5 microns. Escherichia coli, for example, has a size of 0.3-1 by 1-6 microns, Staphylococcus aureus has a diameter of 0.5-1 microns, Bacillus subtilis 0.75 by 2-3 microns. The largest known bacterium is Thiomargarita namibiensis, reaching a size of 750 microns (0.75 mm). The second is Epulopiscium fishelsoni, which has a diameter of 80 microns and a length of up to 700 microns and lives in the digestive tract of the surgical fish Acanthurus nigrofuscus. Achromatium oxaliferum reaches a size of 33 by 100 microns, Beggiatoa alba - 10 by 50 microns. Spirochetes can grow up to 250 microns in length with a thickness of 0.7 microns. At the same time, bacteria are the smallest of the organisms with a cellular structure. Mycoplasma mycoides measures 0.1-0.25 µm, which is the size of large viruses such as tobacco mosaic, vaccinia, or influenza.

Ways of transportation

Among bacteria there are mobile and immobile forms. The mobile ones move by means of wave-like contractions or with the help of flagella (twisted helical threads), which consist of a special flagellin protein. There may be one or more flagella. They are located in some bacteria at one end of the cell, in others - on two or over the entire surface.

But movement is also inherent in many other bacteria that do not have flagella. So, bacteria covered with mucus on the outside are capable of sliding movement.

Some water and soil bacteria without flagella have gas vacuoles in the cytoplasm. There can be 40-60 vacuoles in a cell. Each of them is filled with gas (presumably nitrogen). By regulating the amount of gas in vacuoles, aquatic bacteria can sink into the water column or rise to its surface, and soil bacteria can move in soil capillaries.

Reproduction of bacteria

Most bacteria reproduce by dividing in two, less often by budding, and some (for example, actinomycetes) - with the help of exospores or fragments of mycelium. A known method of multiple division (with the formation of small reproductive cells).

Some bacteria are characterized by a complex development cycle, during which cell morphology may change and dormant forms may form: cysts, spores.

A distinctive feature of bacteria is the ability to multiply rapidly. For example, the doubling time of E. coli (Escherichia coli) cells is 20 minutes. It has been calculated that the progeny of one cell in the case of unlimited growth would exceed the mass of the Earth by 150 times already after 48 hours.

Conclusion: invisible but omnipresent. Simple, but able to take on a variety of forms. Microscopic, but sometimes fatal.

Bacteria are the real invisible masters of the Earth.

Chapter 2. Microflora of human skin

Skin is the outer cover of the human body, protecting the body from a wide range of external influences, participating in respiration. Thermoregulation, metabolic and many other processes.

You cannot even imagine how many microbes live on the skin and in the human body. Basically, they are found on the skin and mucous membranes. The same organisms as in the surrounding air are found on human skin. As a rule, these are sticks, cocci and fungi.

Our skin, due to its constant contact with the external environment, becomes a habitat for a huge number of transient microorganisms. In addition, the skin has its own, permanent and well-studied microflora. Its composition varies in different anatomical zones depending on the oxygen content in the environment surrounding the bacteria (aerobes - anaerobes) and proximity to the mucous membranes (mouth, nose), secretion features and even human clothing. Particularly abundantly populated by microorganisms are those areas of the skin that are protected from the action of light and drying: armpits, interdigital spaces, inguinal folds. The composition of the microflora of the skin and mucous membranes contains: staphylococci, streptococci, enterobacteria, micrococci, etc. For example, Staphylococcus aureus. This bacterium can be picked up anywhere - in hospitals, kindergartens, schools, gyms, shops, and other public places. Microbes streptococci and staphylococci are always on the surface of the human skin. Normally, that is, when the immune system restrains their reproduction, these bacteria are not active and do not irritate the body. However, under the influence of certain conditions, bacteria begin to multiply very quickly. Such a phenomenon can occur if the skin loses its protective properties. For example, mechanical trauma can disrupt the integrity of the skin, and the body remains defenseless against the attack of microbes from the environment.

2.1 The influence of bacteria on the human body

Normally, human skin is inhabited by a huge number of bacteria coexisting peacefully on its surface or in hair follicles.

However, the skin has certain properties that protect it from infection by bacteria. These include a dense and dry keratinized layer, practically impermeable to microorganisms, and a sticky intercellular substance - a complex mixture of lipids that tightly connects the cells of the layer and also protects the skin, clogging the entrance to the hair follicles.

Other factors that stop the penetration of pathogenic microorganisms include the constant renewal of skin cells, the acidic environment, the presence of immunoglobulins in sweat, and various types of skin flora.

Skin infections usually only develop when trauma, overhydration, or inflammatory skin conditions disrupt these protective properties. Organisms that cause skin infections may be part of the permanent skin flora or nearby mucous membranes, or come from external sources such as another person, the environment, or contaminated objects. I will give examples of the negative effect of bacteria on human skin.

Ulcers on the skin are inflammatory elements that form on the skin of a person. With the development and maturation of inflammation, pus is formed. The cause of the formation of abscesses on the skin are specific pathogens that produce pus in the course of their life. Such pathological bacteria include staphylococci and streptococci, which can inhabit the skin and mucous membranes of the oral cavity. Microbes can also be found in soil, water and air. The causative agents of abscesses on the skin have a different structure and look different on a microscope slide.

The skin produces about 500 ml of sweat per day. Sweat itself is odorless, and bacteria are responsible for body odor. Our skin is a microcosm of more than 1000 species of bacteria and about 1 billion individual bacteria.

Healthy skin is characterized by the fact that it is able to fight pathogenic microorganisms that penetrate its surface on its own. This ability of the skin is due to several points, in particular, the chemical composition of the skin. Organic acid compounds that are part of the structure of the skin, sebum and other components of the skin block pathogenic microbes from multiplying. The skin's self-cleansing feature is realized through a combination of organic acids, the ability to renew itself and sunlight acting on the skin. The reasons that provoke the development of ulcers on the skin, the smell of sweat, are numerous and varied. They can be of human origin, that is, develop from the body of the person himself, or they can be due to the negative impact of the environment.

Conclusion: one way or another, due to the impact of these and other factors, the skin loses its ability to resist pathogenic bacteria. Clean skin copes with the attack of harmful microorganisms much more efficiently, while dirty skin has a noticeably reduced immunity. It should be borne in mind that contamination of the skin happens very quickly, in particular if a person is constantly in contact with polluting factors, for example, at the workplace. Even such simple household procedures as the irregular change of bed or underwear can lead to a weakening of the protective function of the skin, to the formation of abscesses, boils and other skin diseases on it.

Chapter 3

The study was conducted on students. Voluntary participation was taken by 6 girls and 6 boys.

The purpose of the study: to study the bacteria on the skin of the hands of boys and girls, as well as to compare the results and draw conclusions.

Equipment: sterile Petri dishes; solid nutrient medium; microscope; slides and coverslips; camera.

Research methodology: the method of transferring bacteria to a Petri dish from the skin of human hands (from the palms and forearms) was applied.

1. Preparation of the nutrient medium. For this we need gelatin and meat broth. Gelatin is a jelly that is used in cooking. Gelatin is made from red and brown algae. It provides an ideal environment for microorganisms.

I mixed the broth with gelatin powder, on fire in a container, brought to a boil, boiled for a minute.

The nutrient medium is considered ready when the powder is completely dissolved, and the liquid itself is transparent.

Let the culture medium cool, then move on to the next steps.

2. Preparation of Petri dishes. These are small flat glass cups. Petri dishes must be sterile, otherwise the results of the bacteria growing experiment will go down the drain. Very carefully poured the nutrient medium into the lower half of the cup with a thin layer, only covering the bottom. Quickly closed the petri dish to prevent airborne bacteria from entering. I let the Petri dishes stand quietly for 30-120 minutes until the nutrient medium cools and hardens (the finished nutrient medium resembles jelly).

3. Planting bacteria in a Petri dish. The gelatin is solid, the Petri dish is at room temperature - everything is ready to continue the experiment! What's next on the plan? That's right, replanting a culture of bacteria in a nutrient medium! All you need is cotton swabs.

Using ordinary cotton buds, I took samples from the tested surfaces. She simply ran the stick where she wanted to take a sample of microflora, then ran the same end of the stick over the surface of the nutrient medium. She transferred what she collected into Petri dishes. Be sure to sign what and where it grows in each particular cup, otherwise I won’t remember later. After a couple of days, I saw interesting and terrible results of my experiment!

5. Place the Petri dishes in a warm and dark place. Let's say for a few days, so that the bacteria can safely grow. The optimum temperature is 20-37 Celsius. I gave the bacteria 7 days to grow.

6. Record your results. A few days later, I noticed that in each Petri dish something of its own was thickly spiked - bacteria, mold, fungi, etc. I wrote down my observations of each cup and drew conclusions about where the most bacteria were.

Indicators	boys	Girls
Amount of children
Absolute number of colonies per forearm
Total colonies	88	34

Results of the study: the number of microorganisms (bacteria) on the skin of the hands of boys is 2.5 times higher than in girls of this age.

In boys and girls, coccal forms of bacteria were found on the palms and on the skin of the forearm. Cocci are spherical bacteria. Their most famous representatives are staphylococci and streptococci. The skin is the natural habitat of staphylococci. Approximately 20% of bacteria live on the skin. Colonies of Staphylococcus aureus were found on the skin of the subjects' hands.

Staphylococci are small round bacteria. Staphylococci feed mainly on decaying food, as well as dying body tissues. A huge number of staphylococci are located on the skin and mucous membranes of a person, but if a person is healthy and his skin and mucous membranes are not damaged, these microbes do not cause any disease. Their aggressive properties appear only in conditions of a weakened organism or if there are damages on the skin or mucous membranes. Streptococci were not found.

Why do boys have more bacteria on their hands? I think that this is due to the fact that in boys the injury to the skin of the hands is higher than in girls, and the slightest damage to the skin is sufficient to open the gates of a staphylococcal infection. Boys also observe hygiene standards worse.

Conclusion: the method of imprints on Petri dishes allows you to visually show and study the bacteria that live on the skin of human hands. The number and nature of bacteria living on human skin depends on the state of the body and factors of the external and internal environment that have a direct impact on the condition of the skin.

Conclusion

The research I have done proves that bacteria can be found on the skin of any person. But the number of bacteria directly depends on what kind of lifestyle a person leads and how he observes the rules of personal hygiene. As Academician V. I. Pokrovsky notes in the Popular Medical Encyclopedia, staphylococci and streptococci living on the surface of the skin of healthy people, under certain conditions, acquire the ability to cause pustular diseases.

It has been established that approximately 80% of infectious diseases are transmitted by contact. The Centers for Disease Control and Prevention provides the following information: 36,000 people die from influenza and influenza-like illnesses every year, so frequent handwashing is our best defense. Washing hands before eating, after going to the toilet and after coming from the street should become mandatory conditions for personal hygiene. The use of hygiene products significantly reduces the number of microorganisms on the surface of human skin. According to literary sources, washing the skin removes up to 1.5 billion microbes from its surface.

Therefore, the observance of the rules of personal hygiene, for each person, should become his conscious need.

Bibliography

Pokrovsky V. I. Popular medical encyclopedia. M.: Soviet Encyclopedia, 1991.

Brekhman I. I. Valeology is the science of health. M.: 1990.

Encyclopedia of home medicine. M.: CJSC Publishing house Tsentrpoligraf: St. Petersburg: Kolita-2, 2002.

Ponomareva I.N., Kornilova O.A. Biology grade 6. M.: Ventana-Graf, 2011.

Frolov M. Yu. Help yourself man. Donetsk: "Donechchina", 2004.

Appendix

Preparation of Petri dishes and culture medium

Planting bacteria in a petri dish

results

The calculation results are presented in the table.

Indicators	boys	Girls
Amount of children
Absolute number of colonies in the palm of your hand
Absolute number of colonies per forearm
Total colonies	88	34

Municipal educational institution "Secondary school No. 6"

Biology essay.

Topic: "Bacteria"

Did the job:

Arseny Sorokin Vladimirovich 8th grade

I Bacteria as living organisms……………………………………………………………….1-2

(Introduction, features structure, behavior and sensory abilities)

II Life processes………………………………………………………………..3-5

(reproduction, nutrition, respiration)

III Additional Information……………………………………………………………………...6

(Main sources of energy, habitat)

IV Interaction of bacteria with other forms of life…………………………………..7-8

(The role of bacteria in nature and human life)

Conclusion………………………………………………………………………………………..9

I Bacteria as living organisms

Introduction

An extensive group of unicellular microorganisms characterized by the absence of an enveloped cell nucleus. At the same time, the genetic material of a bacterium (DNA) occupies a well-defined place in the cell - a zone called the nucleoid. Organisms with this cell structure are called prokaryotes (“pre-nuclear”), in contrast to all the others - eukaryotes (“true nuclear”), whose DNA is located in the nucleus surrounded by a shell.

Bacteria, once considered microscopic plants, are now classified as a separate kingdom, Monera, one of five in the current classification system, along with plants, animals, fungi, and protists.

The structure of bacteria

A bacterial cell is usually 70-80% water. In the dry residue, protein accounts for 50%, cell wall components 10-20%, RNA 10-20%, DNA 3-4% and lipids 10%. At the same time, on average, the amount of carbon is 50%, oxygen 20%, nitrogen 14%, hydrogen 8%, phosphorus 3%, sulfur and potassium 1% each, calcium and magnesium 0.5% each and iron 0.2%.

With few exceptions (mycoplasmas), bacterial cells are surrounded by a cell wall that defines the shape of bacteria and performs mechanical and important physiological functions. Its main component is a complex biopolymer murein (peptidoglycan). Depending on the composition and structure of the cell wall, bacteria behave differently when stained according to the X. K. Gram method, which served as the basis for dividing bacteria into gram-positive, gram-negative, and devoid of a cell wall (for example, mycoplasmas). The former are distinguished by a large (up to 40 times) murein content and a thick wall; in gram-negatives, it is much thinner and is covered on the outside by an outer membrane consisting of proteins, phospholipids and lipopolysaccharides and, apparently, involved in the transport of substances. Many bacteria on the surface have villi (fimbriae, pili) and flagella that ensure their movement. Often the cell walls of bacteria are surrounded by mucous capsules of varying thickness, formed mainly by polysaccharides (sometimes glycoproteins or polypeptides). In a number of bacteria, so-called. S-layers (from the English surface - surface), lining the outer surface of the cell membrane with evenly packed protein structures

correct form.

The cytoplasmic membrane, which separates the cytoplasm from the cell wall, serves as an osmotic barrier of the cell and regulates the transport of substances. The processes of respiration, nitrogen fixation, chemosynthesis, etc. are carried out in it. Often it forms invaginations - mesosomes. Biosynthesis of the cell wall, sporulation, etc. are also associated with the cytoplasmic membrane and its derivatives. Flagella and genomic DNA are attached to it.

The bacterial cell is organized quite simply. In the cytoplasm of many bacteria there are inclusions represented by various kinds of vesicles (vesicles) formed as a result of invagination of the cytoplasmic membrane. Phototrophic, nitrifying, and methane-oxidizing bacteria are characterized by a developed network of cytoplasmic membranes in the form of undivided vesicles resembling eukaryotic chloroplast grana. In the cells of some water-dwelling bacteria, there are gas vacuoles (aerosomes) that act as density regulators. In many bacteria, inclusions of reserve substances were found - polysaccharides, poly-p-hydroxybutyrate, polyphosphates, sulfur, etc. There are also ribosomes in the cytoplasm (from 5 to 50 thousand). Some bacteria (for example, many cyanobacteria) have carboxysomes - bodies that contain an enzyme involved in CO2 fixation. In the so-called. Parasporal bodies of some spore-forming bacteria contain a toxin that kills insect larvae.

Sensory functions and behavior

Many bacteria have chemical receptors that detect changes in the acidity of the environment and the concentration of various substances, such as sugars, amino acids, oxygen and carbon dioxide. Each substance has its own type of such “taste” receptors, and the loss of one of them as a result of mutation leads to partial “taste blindness”. Many motile bacteria also respond to temperature fluctuations, and photosynthetic species to changes in light. Some bacteria perceive the direction of magnetic field lines, including the Earth's magnetic field, with the help of magnetite particles (magnetic iron ore - Fe3O4) present in their cells. In water, bacteria use this ability to swim along lines of force in search of a favorable environment.

Conditioned reflexes in bacteria are unknown, but they have a certain kind of primitive memory. While swimming, they compare the perceived intensity of the stimulus with its previous value, i.e. determine whether it has become larger or smaller, and, based on this, maintain the direction of movement or change it.

II Life processes

reproduction

Bacteria reproduce asexually: the DNA in their cell is replicated (doubled), the cell divides in two, and each daughter cell receives one copy of the parent's DNA. Bacterial DNA can also be transferred between non-dividing cells. At the same time, their fusion (as in eukaryotes) does not occur, the number of individuals does not increase, and usually only a small part of the genome (the complete set of genes) is transferred to another cell, in contrast to the "real" sexual process, in which the descendant receives a complete set of genes from each parent.

Such DNA transfer can be carried out in three ways. During transformation, the bacterium absorbs DNA from the environment that got there during the destruction of other bacteria or deliberately by the experimenter. The process is called transformation, because in the early stages of its study, the main focus was on the transformation in this way of harmless organisms into virulent ones. Fragments of DNA can also be transferred from bacteria to bacteria by special viruses called bacteriophages. This is called transduction. There is also a process that resembles fertilization and is called conjugation: bacteria are connected to each other by temporary tubular outgrowths (copulatory fimbria), through which DNA passes from the “male” cell to the “female”.

Sometimes bacteria contain very small extra chromosomes - plasmids, which can also be transferred from individual to individual. If at the same time plasmids contain genes that cause resistance to antibiotics, they speak of infectious resistance. It is important from a medical point of view, because it can spread between different species and even genera of bacteria, as a result of which the entire bacterial flora, say the intestines, becomes resistant to the action of certain drugs.

Bacteria nutrition

The peculiarity of the process of nutrition of bacteria is that the supply of nutrients to the cell occurs over the entire surface, which is very large compared to the total size of the bacterium. The second feature is the extraordinary speed of metabolic processes and the third is high adaptation to changing environmental conditions.

A variety of conditions for the existence of microbes determines various types of nutrition. They are determined based on the assimilation of two of the four

essential organogens - carbohydrate and nitrogen. source of hydrogen and

Bacteria are divided into two groups according to their ability to assimilate nitrogen: aminoautotrophs and aminoheterotrophs. Aminoautotrophs use the molecular nitrogen of the air. Bacteria of this group - nitrogen-fixing soil and nodule bacteria - are the only living creatures that assimilate free nitrogen and take an active part in the nitrogen cycle in nature. Aminoheterotrophs obtain nitrogen from organic compounds - complex proteins. Aminoheterotrophs include all pathogenic microorganisms and most saprophytes.

Breath bacteria

The processes of respiration are closely related to the nutrition of bacteria, providing the necessary energy for the implementation of the physiological functions of the cell. The essence of the process of respiration of bacteria lies in the totality of biochemical reactions, during which the formation of ATP takes place, without which the process of metabolism, which proceeds with the expenditure of energy, is impossible. ATP is the universal carrier of chemical energy between the processes that release energy and the reactions that use them. During respiration - the process of biological oxidation of bacteria - the same compounds are consumed as for the construction of individual structural components of the cell, but first of all - sugars, alcohols, organic acids, fats, etc.

Most bacteria use free oxygen in the process of respiration. Such microorganisms are called aerobic. Aerobic type of respiration is characterized by the fact that the oxidation of organic compounds occurs with the participation of atmospheric oxygen with the release of a large number of calories. Molecular oxygen acts as an acceptor

hydrogen formed during the aerobic breakdown of these compounds.

An example is the oxidation of glucose under aerobic conditions, which results in the release of large amounts of energy.

The process of anaerobic respiration of microbes is that bacteria obtain energy from redox reactions, in which the hydrogen acceptor is not oxygen, but inorganic compounds - nitrate or sulfate.

Many bacteria can exist in aerobic and anaerobic conditions. Such microorganisms are called facultative anaerobes. For example, cocci, Escherichia coli and other facultative anaerobes have a complete set of respiratory enzymes that ensure their existence in both oxygen and anoxic environments. Facultative anaerobes have the so-called nitrate respiration, since the nitrate formed during the oxidation of organic compounds is reduced to molecular nitrogen and ammonia.

III Additional information

Energy sources

According to energy sources, phototrophs are distinguished - bacteria for which the source of energy is sunlight, and chemotrophs - bacteria that obtain energy due to the chemical oxidation of substances. However, not all compounds that are necessary for bacteria in biological processes can be synthesized by the cell itself. When compiling nutrient media, it is necessary to add substances called growth factors. These are various vitamins, amino acids (without which protein synthesis is impossible), pyrimidine bases (precursors of nucleic acids), etc. Microorganisms that need one or more growth factors are called auxotrophic, in contrast to prototrophic bacteria that do not need these compounds. and are capable of synthesizing them.

habitats for bacteria

Bacteria live in soil, water, humans and animals. Various groups of bacteria can develop in conditions that are not available to other organisms. The qualitative and quantitative composition of bacteria living in the external environment depends on many conditions: the pH of the environment, temperature, the presence of nutrients, humidity, aeration, and the presence of other microorganisms. The more various organic compounds are contained in the medium, the greater the number of bacteria can be found in it. In unpolluted soils and waters, a relatively small number of saprophytic forms of bacteria, microbacteria, and cocci forms are found. In the water there are various spore-forming and non-spore-forming bacteria and specific aquatic bacteria - aquatic vibrios, filamentous bacteria, etc. Various anaerobic bacteria live in the silt, at the bottom of reservoirs. Among the bacteria living in water and soil, there are nitrogen-fixing, nitrifying, denitrifying cellulose bacteria, etc. Bacteria growing at high salt concentrations and high pressure live in the seas and oceans, and luminous species are found. In polluted waters and soil, in addition to soil and water saprophytes, there are a large number of bacteria that live in humans and animals - enterobacteria, clostridia, etc. An indicator of fecal contamination is usually the presence of Escherichia coli.

IV Interaction of bacteria with other forms of life

The role of bacteria in nature and human life

Bacteria play an important role on Earth. Due to the wide distribution of bacteria and the peculiarity of the metabolic activity of many of their species, they are of exceptionally great importance in the cycle of substances in nature. All organic compounds and a significant part of inorganic ones undergo significant changes with the help of bacteria. This role in nature is of global importance. Appearing on Earth before all organisms (more than 3.5 billion years ago), they created the living shell of the Earth and continue to actively process living and dead organic matter, involving their metabolic products in the circulation of substances. The cycle of substances in nature is the basis for the existence of life on Earth.

The decay of all plant and animal remains and the formation of humus and humus are also produced mainly by bacteria. Bacteria are a powerful biotic factor in nature.

The soil-forming work of bacteria is of great importance. The first soil on our planet was created by bacteria. However, in our time, the condition and quality of the soil depend on the functioning of soil bacteria. Particularly important for soil fertility are the so-called nitrogen-fixing nodule bacteria-symbionts of leguminous plants. They saturate the soil with valuable nitrogen compounds.

Bacteria purify dirty wastewater by breaking down organic matter and converting it into harmless inorganic matter. This property of bacteria is widely used in the operation of wastewater treatment plants.

In many cases, bacteria can be harmful to humans. So, saprotrophic bacteria spoil food products. To protect products from spoilage, they are subjected to special processing. If this is not done, food poisoning may occur.

Among bacteria, there are many disease-causing (pathogenic) species that cause diseases in humans, animals or plants. Typhoid fever is caused by the Salmonella bacterium, and dysentery by the Shigella bacterium. Pathogenic bacteria are carried through the air with droplets of the saliva of a sick person when sneezing, coughing, and even during normal conversation (diphtheria, whooping cough). Some disease-causing bacteria are very resistant to desiccation and persist in the dust for a long time.

(tuberculosis bacillus). Bacteria of the genus Clostridium live in dust and soil.

- causative agents of gas gangrene and tetanus. Some bacterial diseases are transmitted through physical contact with a sick person (venereal disease, leprosy). Often, pathogenic bacteria are transmitted to humans through so-called vectors. For example, flies, crawling through sewage, collect thousands of pathogenic bacteria on their paws, and then leave them on the products consumed by humans.

Diseases can also be associated with the penetration of bacteria into wounds. Soil-contaminated deep wounds harbor bacteria that cause gas gangrene and tetanus. These diseases are very dangerous and often fatal. Superficial wounds and burns are easily infected with staphylococci and streptococci, which cause purulent inflammation.

The activity of some bacteria is used by man in the production of medicines, various organic substances, and new food products. Special types of bacteria produce strong antibiotics (streptomycin, tetracycline, etc.) - substances that kill or inhibit the development of pathogens.

Fermentation has been known to people since time immemorial. For thousands of years they have used lactic acid fermentation in the manufacture of various dairy products, cheeses; alcoholic fermentation - in the manufacture of wine, brewing, sauerkraut, cooking vinegar. At the same time, they did not suspect that fermentation is the result of the vital activity of bacteria.

Conclusion

Bacteria existed before the advent of man and will remain after him. They gave life to everything that surrounds us: plants (creating the soil), animals (having combined into tissues and forming organs in the process of evolution, as well as giving them food), and most importantly, humans. They helped us to live by providing new food products (cheese, wine, cottage cheese), fertilizing the soil with humus during the processing of "garbage", and then giving "tips" to fight the diseases that they also created.

They are our true friends and worst enemies. Many can kill us, while others help us survive. Then a paradox arises, and with it the question: “Who are bacteria to us?”

No one will answer this question unequivocally, and probably there will not be one who will find the answer.