Types of anaerobic bacteria. What are anaerobic bacteria and anaerobic infections

A BRIEF HISTORY OF MICROBIOLOGY

The study of the history of science makes it possible to trace the processes of its emergence and development, to understand the continuity of ideas, the level state of the art science and prospects for further progress. The course of medical microbiology mainly outlines the history of this branch of microbiology.

The first person, before whose astonished eyes the invisible mysterious world of microscopic creatures was opened, was the Dutch naturalist Anthony Leeuwenhoek (1632-1723). In September 1675, he reported to the Royal Society of London that in rainwater that stood in the air, he managed to find the smallest living animals (viva animalcula), which differed from each other in size and movement. In subsequent letters, he reported that such creatures are found in hay infusions, stool, and plaque. He wrote about living animals of dental plaque. With the greatest amazement, I saw in this material (dental plaque) a lot of the smallest animals moving very briskly. There are more of them in my mouth than there are people in the United Kingdom. Leeuwenhoek published his observations in the form of letters, which were later summarized by him in the book Secrets of Nature, discovered by Antony Leeuwenhoek.

The idea of ​​the presence in nature of invisible living beings appeared among many researchers. Back in the 6th century BC. h. Hippocrates, 16th century A.D. e. Giralamo Frakastro and early XVII centuries, Athanasius Kircher suggested that the cause of infectious diseases are invisible living beings. But none of them had any evidence of this. Leeuwenhoek demonstrated microbes under a microscope, and in 1683 presented drawings of bacteria for the first time.

Leeuwenhoek's discovery attracted everyone's attention. It was the basis for the development of microbiology, the study of the forms of microbes and their distribution in the external environment. This so-called morphological period, which lasted almost two decades, was unproductive, since the optical instruments of that time did not make it possible to distinguish one type of microbe from another, and could not give an idea of ​​the role of microbes in nature.

Constructive metabolism of bacteria.

For micro-organisms to grow and reproduce, their habitat must have nutrient materials and available sources of energy.

Nutrition is the process by which a bacterial cell receives food from environment components necessary for the construction of its biopolymers.

According to the source of C, microorganisms are divided into:

Autotrophs (feeding on its own) or lithotrophs (litho - stone) - microorganisms that are capable of synthesizing complex ones from simple inorganic organic compounds(the only source of carbon is CO2)

Heterotrophs (feeding at the expense of others) or organotrophs - cannot synthesize complex organic compounds from simple inorganic ones, they need the intake of ready-made organic compounds (they extract carbon from glucose, polyhydric alcohols, less often hydrocarbons, amino acids, organic acids). Heterotrophs are divided into:

Saprophytes (rotten, plant) - get ready-made organic compounds from dead nature, decomposing organic waste, animal and human corpses (environmental orderlies)

According to the ability to absorb nitrogen, microorganisms are classified:

Aminoautotrophs - use molecular nitrogen from the air (nitrogen-fixing bacteria) or ammonium salts, nitrates, nitrites (ammonifying bacteria)

Aminoheterotrophs - get nitrogen from organic compounds (amino acids, complex proteins)

Only small molecules of amino acids, glucose, etc. can penetrate into the cytoplasm of cells. Therefore, macromolecules are pre-treated with enzymes that the cell releases into the external environment (exoenzymes). Only then are they available for use.

Nutrient pathways:

Simple diffusion - goes without energy costs, nutrients come from places with a higher concentration to places with a lower concentration

Facilitated diffusion - the transfer of nutrients from places with a higher concentration to places with a lower concentration, but with the participation of carrier molecules (permeases) without energy expenditure, but at a faster rate than with simple diffusion

Active transport - the transfer is carried out with the help of permeases, but with energy costs, while the transfer can be carried out from places with a lower concentration to places with a higher concentration.

Radical transfer - accompanied by translocation chemical groups, resulting in a chemical modification of the transferred substance. Radical transport is similar to active transport.

Phagocytosis and pinocytosis - enveloping solid and liquid nutrients with the cytoplasm of a microbial cell, followed by their digestion.

Metabolism or metabolism consists of the following processes: 1) assimilation (anabolism) - accompanied by an increase in the complexity of compounds (synthesis of substances with energy consumption). 2) dissimilation (catabolism) - splitting of complex compounds into simple ones, which are then used for subsequent synthesis, and part is released into the external environment, while freeing up the energy necessary for the life of the microbial cell.

4 Energy metabolism. However, the vast majority of prokaryotes receive energy through dehydrogenation. Aerobes need free oxygen for this purpose. Obligate (strict) aerobes cannot live and reproduce in the absence of molecular oxygen, since they use it as an electron acceptor. ATP molecules they are formed by oxidative phosphorylation with the participation of cytochrome oxidases, flavin-dependent oxidases and dehydrogenases. In this case, if the final electron acceptor is oxygen, significant amounts of energy are released

Anaerobes receive energy in the absence of oxygen access by accelerated, but not complete splitting nutrients. Obligate anaerobes (tetanus, botulism) cannot tolerate even traces of oxygen. They can form ATP as a result of the oxidation of carbohydrates, proteins and lipids by substrate phosphorylation to pyruvate. In this case, a relatively small amount of energy is released.

There are facultative anaerobes that can grow and multiply both in the presence of atmospheric oxygen and without it. They form ATP by oxidative and substrate phosphorylation.

Aerobic and anaerobic microorganisms.

Different bacteria react differently to the presence or absence of free oxygen. On this basis, they are divided into three groups: aerobes, anaerobes and facultative anaerobes. Strict aerobes, for example, Pseudomonas aeruginosa, can develop only in the presence of free oxygen. Anaerobes, eg. causative agents of gas gangrene, tetanus, Develop without access to free oxygen, the presence of which depresses their vital activity. Finally, facultative anaerobes, for example, causative agents of intestinal infections, develop in both oxygen and anoxic environments. Aerobicity or anaerobicity of bacteria is determined by the way they receive the energy necessary to ensure vital processes. Some bacteria (photosynthetic) are able, like plants, to directly use the energy of sunlight. The rest (chemosynthetic) receive energy during various chemical reactions. There are bacteria (chemoautotrophs) that oxidize inorganic substances(ammonia, sulfur and iron compounds, etc.). But for most bacteria, transformations of organic compounds serve as an energy source: carbohydrates, proteins, fats, etc. Aerobes use biological oxidation reactions involving free oxygen (respiration), as a result of which organic compounds are oxidized to carbon dioxide and water. Anaerobes obtain energy from the breakdown of organic compounds without the participation of free oxygen. This process is called fermentation. During fermentation, in addition to carbon dioxide, various compounds are formed, for example, alcohols, lactic, butyric and other acids, acetone.

6 morphology and classification of bacteria! Bacteria (from lat. bacteria - stick) are single-celled organisms lacking chlorophyll. By biological properties- prokaryotes. Sizes from 0.1 to 0.15 micrometers to 16-28 microns. The size and shape of bacteria are inconsistent and change with the influence of the environment.

By appearance Bacteria are divided into 4 forms: spherical (cocci), rod-shaped (bacteria, bacilli and clostridia), convoluted (vibrios, spirilla, spirochetes) and filamentous (chlamydobacteria).

1. Cocci (from lat. coccus - grain) - a spherical microorganism, it can be spherical, elliptical, bean-shaped and lanceolate. According to the location, nature of division and biological properties, cocci are divided into micrococci, diplococci, streptococci, tetracocci, sarcina, staphylococci.

Micrococci are characterized by a single, paired or random arrangement of cells. They are saprophytes, inhabitants of water, air.

Diplococci (from lat. diplodocus - double) divide in one plane and form cocci, connected in two individuals. Diplococci include meningococci - the causative agents of epidemic meningitis and gonococci - the causative agents of gonorrhea and blennorrhea.

Streptococci (from lat. streptococcus - twisted), dividing in the same plane, are arranged in chains of various lengths. There are streptococci that are pathogenic for humans and cause various diseases.

Tetracocci (from lat. tetra - four), located in 4, are divided in two mutually perpendicular planes.

Rarely found as pathogens in humans.

Sardines (from Latin saris - I bind) are coccal forms that divide in three mutually perpendicular planes and look like bales of 8-16 or more cells. Often found in the air. There are no pathogenic forms.

Staphylococci (from lat. staphylococcus) - clustered cocci, dividing in different planes; arranged in irregular clusters.

Some species cause disease in humans and animals.

Bacteria appeared over 3.5 billion years ago and were the first living organisms on our planet. It is thanks to aerobic and anaerobic species of bacteria that life originated on Earth.

Today they are one of the most species-diverse and widespread group of prokaryotic (non-nuclear) organisms. Different respiration made it possible to subdivide them into aerobic and anaerobic, and nutrition - into heterotrophic and autotrophic prokaryotes.

Classification division of prokaryotes

The species diversity of these non-nuclear single-celled organisms is enormous: science has described only 10,000 species, and there are supposedly more than a million species of bacteria. Their classification is extremely complex and is carried out based on the commonality of the following features and properties:

• morphological - form, mode of movement, ability to sporulate, and others);
• physiological - breathing with oxygen (aerobic) or an oxygen-free variant ( anaerobic bacteria), by the nature of metabolic products and others;
• biochemical;
• similarity of genetic characteristics.

For example, the morphological classification by appearance subdivides all bacteria as:

• rod-shaped;
• winding;
• spherical.

The physiological classification in relation to oxygen divides all prokaryotes into:

• anaerobic - microorganisms whose respiration does not require the presence of free oxygen;
• aerobic - microorganisms that need oxygen for their life.

Anaerobic prokaryotes

Anaerobic microorganisms fully correspond to their name - the prefix an-denies the meaning of the word, aero is air and b-life. It turns out - airless life, organisms whose breathing does not need free oxygen.

Anoxic microorganisms are divided into two groups:

• facultative anaerobic - able to exist both in an environment containing oxygen, and in its absence;
• obligate microorganisms - dying in the presence of free oxygen in the environment.

The classification of anaerobic bacteria subdivides the obligate group according to the possibility of sporulation into the following:

• spore-forming clostridia - gram-positive bacteria, most of which are mobile, characterized by intensive metabolism and high variability;
• non-clostridial anaerobes are gram-positive and negative bacteria that are part of the human microflora.

Clostridia properties

Spore-forming anaerobic bacteria are found in large numbers in the soil and in the gastrointestinal tract of animals and humans. Among them, more than 10 species are known that are toxic to humans. These bacteria produce highly active exotoxins specific to each species.

Although the infectious agent may be one species anaerobic microorganisms, intoxication by various microbial associations is more characteristic:

• several types of anaerobic bacteria;
• anaerobic and aerobic microorganisms (most often clostridia and staphylococci).

Bacterial culture

It is quite natural in the oxygen environment familiar to us that in order to obtain obligate aerobes, it is necessary to use special equipment and microbiological media. In fact, the cultivation of anoxic microorganisms is reduced to the creation of conditions under which the access of air to the media where the cultivation of prokaryotes is performed is completely blocked.

In the case of microbiological analysis for obligate anaerobes, the methods of sampling and the method of transporting the sample to the laboratory are extremely important. Since obligate microorganisms will immediately die under the influence of air, the sample must be stored either in a sealed syringe or in specialized media designed for such transportation.

Aerophilic microorganisms

Aerobes are called microorganisms whose respiration is impossible without free oxygen in the air, and their cultivation takes place on the surface of nutrient media.

According to the degree of dependence on oxygen, all aerobes are divided into:

• obligate (aerophiles) - able to develop only at a high concentration of oxygen in the air;
• facultative aerobic microorganisms that develop even with a reduced amount of oxygen.

Properties and features of aerobes

Aerobic bacteria live in soil, water and air and are actively involved in the cycle of substances. The respiration of bacteria, which are aerobes, is carried out by direct oxidation of methane (CH 4), hydrogen (H 2), nitrogen (N 2), hydrogen sulfide (H 2 S), iron (Fe).

Obligate aerobic microorganisms that are pathogenic to humans include tubercle bacillus, tularemia pathogens, and vibrio cholerae. All of them require high levels of oxygen to survive. Facultative aerobic bacteria such as salmonella are able to respire with very little oxygen.

Aerobic microorganisms that carry out their respiration in an oxygen atmosphere are able to exist in a very wide range at a partial pressure of 0.1 to 20 atm.

Growing Aerobes

The cultivation of aerobes involves the use of a suitable nutrient medium. Necessary conditions are also the quantitative control of the oxygen atmosphere and the creation of optimal temperatures.

The respiration and growth of aerobes is manifested as the formation of turbidity in liquid media or, in the case of dense media, as the formation of colonies. On average, it takes about 18 to 24 hours to grow aerobes under thermostatic conditions.

General properties for aerobes and anaerobes

1. All these prokaryotes do not have a pronounced nucleus.
2. They reproduce either by budding or division.
3. Carrying out respiration, as a result of the oxidative process, both aerobic and anaerobic organisms decompose huge masses of organic residues.
4. Bacteria are the only living things whose respiration binds molecular nitrogen into an organic compound.
5. Aerobic organisms and anaerobes are capable of respiration over a wide range of temperatures. There is a classification according to which non-nuclear unicellular organisms subdivided into:

• psychrophilic - living conditions in the region of 0 ° C;
• mesophilic - vital temperature from 20 to 40 ° C;
• thermophilic - growth and respiration occurs at 50-75 ° C.

Organisms that are able to obtain energy in the absence of oxygen are called anaerobes. Moreover, the group of anaerobes includes both microorganisms (protozoa and a group of prokaryotes) and macroorganisms, which include some algae, fungi, animals and plants. In our article, we will take a closer look at anaerobic bacteria that are used to clean Wastewater in local treatment facilities. Since aerobic microorganisms can be used along with them in wastewater treatment plants, we will compare these bacteria.

What are anaerobes, we figured it out. Now it is worth understanding what types they are divided into. In microbiology, the following classification table for anaerobes is used:

• Facultative microorganisms. Facultative anaerobic bacteria are called bacteria that can change their metabolic pathway, that is, they are able to change respiration from anaerobic to aerobic and vice versa. It can be argued that they live facultatively.
• Capneistic representatives of the group able to live only in an environment with a low content of oxygen and a high content of carbon dioxide.
• Moderately strict organisms can survive in an environment containing molecular oxygen. However, they are unable to reproduce here. Macroaerophiles can both survive and multiply in an environment with a reduced partial pressure of oxygen.
• Aerotolerant microorganisms differ in that they cannot live facultatively, that is, they are not able to switch from anaerobic respiration to aerobic respiration. However, they differ from the group of facultative anaerobic microorganisms in that they do not die in an environment with molecular oxygen. This group includes most butyric bacteria and some types of lactic acid microorganisms.
• obligate bacteria quickly perish in an environment containing molecular oxygen. They can only live in conditions complete isolation From him. This group includes ciliates, flagellates, some types of bacteria and yeasts.

Effect of oxygen on bacteria

Any environment containing oxygen aggressively affects organic life forms. The thing is that in the process of vital activity of various life forms or due to the influence of certain types of ionizing radiation, active forms oxygen, which are more toxic than the molecular substance.

The main determining factor for the survival of a living organism in an oxygen environment is the presence of an antioxidant functional system that is capable of elimination. Typically, such protective functions are provided by one or several enzymes at once:

• cytochrome;
• catalase;
• superoxide dismutase.

At the same time, some anaerobic bacteria of a facultative species contain only one type of enzyme - cytochrome. Aerobic microorganisms have as many as three cytochromes, so they feel great in an oxygen environment. And obligate anaerobes do not contain cytochrome at all.

However, some anaerobic organisms can act on their environment and create a suitable redox potential for it. For example, certain microorganisms reduce the acidity of the environment from 25 to 1 or 5 before breeding. This allows them to protect themselves with a special barrier. And aerotolerant anaerobic organisms, which release hydrogen peroxide in the course of their life, can increase the acidity of the environment.

Important: to provide additional antioxidant protection, bacteria synthesize or accumulate low molecular weight antioxidants, which include vitamins A, E and C, as well as citric and other types of acids.

How do anaerobes get energy?

1. Some microorganisms obtain energy from the catabolism of various amino acid compounds, such as proteins and peptides, as well as the amino acids themselves. Typically, this process of releasing energy is called putrefaction. And the environment itself, in the energy exchange of which many processes of catabolism of amino acid compounds and amino acids themselves are observed, is called a putrefactive environment.
2. Other anaerobic bacteria are able to break down hexoses (glucose). In this case, different splitting methods can be used:
   • glycolysis. After it, fermentation processes occur in the environment;
   • oxidative pathway;
   • Entner-Doudoroff reactions that take place under the conditions of mannanoic, hexuronic or gluconic acid.

In this case, only anaerobic representatives can use glycolysis. It can be divided into several types of fermentation, depending on the products that are formed after the reaction:

• alcoholic fermentation;
• lactic fermentation;
• type of enterobacteria formic acid;
• butyric fermentation;
• propionic acid reaction;
• processes with the release of molecular oxygen;
• methane fermentation (used in septic tanks).

Features of anaerobes for a septic tank

Anaerobic septic tanks use microorganisms that are able to process wastewater without oxygen. As a rule, in the compartment where the anaerobes are located, the processes of wastewater decay are significantly accelerated. As a result of this process, solid compounds fall to the bottom in the form of sediment. At the same time, the liquid component of the wastewater is qualitatively cleaned from various organic impurities.

During the life of these bacteria, a large number of solid compounds are formed. All of them settle at the bottom of the local treatment plant, so it needs regular cleaning. If cleaning is not carried out in a timely manner, then the efficient and well-coordinated operation of the treatment plant can be completely disrupted and put out of action.

Attention: the sludge obtained after cleaning the septic tank should not be used as fertilizer, as it contains harmful microorganisms that can harm the environment.

Since anaerobic representatives of bacteria produce methane during their life activity, treatment facilities that work with the use of these organisms must be equipped with efficient system ventilation. Otherwise, an unpleasant odor can spoil the surrounding air.

Important: the efficiency of wastewater treatment using anaerobes is only 60-70%.

Disadvantages of using anaerobes in septic tanks

Anaerobic representatives of bacteria, which are part of various biological products for septic tanks, have the following disadvantages:

1. The waste that is generated after the processing of sewage by bacteria is not suitable for fertilizing the soil due to the content of harmful microorganisms in them.
2. Since a large amount of dense sediment is formed during the life of anaerobes, its removal must be carried out regularly. To do this, you will have to call the vacuum cleaners.
3. Wastewater treatment using anaerobic bacteria is not complete, but only a maximum of 70 percent.
4. A sewage treatment plant operating with these bacteria can emit a very unpleasant odor, which is due to the fact that these microorganisms emit methane during their life.

The difference between anaerobes and aerobes

The main difference between aerobes and anaerobes is that the former are able to live and reproduce in conditions with a high oxygen content. Therefore, such septic tanks are necessarily equipped with a compressor and an aerator for pumping air. As a rule, these local wastewater treatment plants do not emit such an unpleasant odor.

In contrast, anaerobic representatives (as the table of microbiology described above shows) do not need oxygen. Moreover, some of their species are able to die with a high content of this substance. Therefore, such septic tanks do not require pumping air. For them, only the removal of the resulting methane is important.

Another difference is the amount of sediment formed. In systems with aerobes, the amount of sludge is much less, so the cleaning of the structure can be carried out much less often. In addition, the septic tank can be cleaned without calling the vacuum trucks. To remove thick sediment from the first chamber, you can take an ordinary net, and to pump out the activated sludge formed in the last chamber, it is enough to use a drainage pump. Moreover, the activated sludge from the treatment plant using aerobes can be used to fertilize the soil.

Aerobic bacteria are microorganisms that need free oxygen for normal life. Unlike all anaerobes, they also participate in the process of generating the energy they need for reproduction. These bacteria do not have a pronounced nucleus. They reproduce by budding or fission and, when oxidized, form various toxic products of incomplete reduction.

Features of aerobes

Not many people know that aerobic bacteria ( in simple terms Aerobes are organisms that can live in soil, air, and water. They are actively involved in the circulation of substances and have several special enzymes that ensure their decomposition (for example, catalase, superoxide dismutase, and others). The respiration of these bacteria is carried out by direct oxidation of methane, hydrogen, nitrogen, hydrogen sulfide, and iron. They are able to exist in a wide range at a partial pressure of 0.1-20 atm.

The cultivation of aerobic gram-negative and gram-positive bacteria implies not only the use of a suitable nutrient medium for them, but also the quantitative control of the oxygen atmosphere and the maintenance of optimal temperatures. For each microorganism of this group, there is both a minimum and a maximum oxygen concentration in the environment surrounding it, which is necessary for its normal reproduction and development. Therefore, both a decrease and an increase in the oxygen content beyond the “maximum” limit leads to the termination of the vital activity of such microbes. All aerobic bacteria die at an oxygen concentration of 40 to 50%.

Types of aerobic bacteria

According to the degree of dependence on free oxygen, all aerobic bacteria are divided into the following types:

1. obligate aerobes- these are "unconditional" or "strict" aerobes that are able to develop only when there is a high concentration of oxygen in the air, since they receive energy from oxidative reactions with his participation. These include:

2. Facultative aerobes- microorganisms that develop even at a very low amount of oxygen. belongs to this group.

Anaerobes are microbes that can grow and multiply in the absence of free oxygen. The toxic effect of oxygen on anaerobes is associated with the suppression of the activity of a number of bacterial. There are facultative anaerobes that can change the anaerobic type of respiration to aerobic, and strict (obligate) anaerobes, which have only anaerobic type of respiration.

When cultivating strict anaerobes, chemical methods are used to eliminate oxygen: substances capable of absorbing oxygen (for example, an alkaline solution of pyrogallol, sodium hydrosulfite) are added to the environment surrounding anaerobes, or they are introduced into the composition of substances capable of restoring incoming oxygen (for example, etc.) . It is possible to provide anaerobes by physical methods: mechanically remove from nutrient media before sowing by boiling, followed by filling the surface of the medium with liquid, and also use an anaerostat; inoculate by injection into a tall column of nutrient agar, then pouring it with viscous vaseline oil. The biological way to provide anoxic conditions for anaerobes is the combined, joint sowing of crops and anaerobes.

Pathogenic anaerobes include rods, pathogens (see Clostridia). See also .

Anaerobes are microorganisms that can exist and develop normally without access to free oxygen.

The terms "anaerobes" and "anaerobiosis" (life without access to air; from the Greek negative prefix anaer - air and bios-life) were proposed by L. Pasteur in 1861 to characterize the conditions for the existence of microbes of butyric fermentation discovered by him. Anaerobes have the ability to decompose organic compounds in an oxygen-free environment and thus obtain the necessary energy for their life.

Anaerobes are widely distributed in nature: they live in soil, pond silt, compost heaps, in the depths of wounds, in the intestines of people and animals - wherever decomposition occurs. organic matter without air access.

In relation to oxygen, anaerobes are divided into strict (obligate) anaerobes, which are not able to grow in the presence of oxygen, and conditional (facultative) anaerobes, which can grow and develop both in the presence of oxygen and without it. The first group includes most anaerobes from the genus Clostridium, bacteria of lactic and butyric fermentation; to the second group - cocci, fungi, etc. In addition, there are microorganisms that require a small concentration of oxygen for their development - microaerophiles (Clostridium histolyticum, Clostridium tertium, some representatives of the genus Fusobacterium and Actinomyces).

The genus Clostridium unites about 93 species of rod-shaped gram-positive bacteria that form terminal or subterminal spores (tsvetn. Fig. 1-6). Pathogenic clostridia include Cl. perfringens, Cl. oedema-tiens, Cl. septicum, Cl. histolyticum, Cl. sordellii, which is the causative agent of anaerobic infection (gas gangrene), pulmonary gangrene, gangrenous appendicitis, postpartum and post-abortion complications, anaerobic septicemia, and food poisoning (Cl. perfringens, types A, C, D, F).

Pathogenic anaerobes are also Cl. tetani is the causative agent of tetanus and Cl. botulinum is the causative agent of botulism.

The genus Bacteroides includes 30 species of rod-shaped, non-spore-forming, gram-negative bacteria, most of them are strict anaerobes. Representatives of this genus are found in the intestinal and genitourinary tracts of humans and animals; some species are pathogenic, causing septicemia and abscesses.

Anaerobes of the genus Fusobacterium (small sticks with a thickening at the ends, not forming spores, gram-negative), which are inhabitants of the oral cavity of humans and animals, in association with other bacteria cause necrobacillosis, Vincent's tonsillitis, gangrenous stomatitis. Anaerobic staphylococci of the genus Peptococcus and streptococci of the genus Peptostreptococcus are found in healthy people in the respiratory tract, mouth, vagina, and intestines. Anaerobic cocci cause various purulent diseases: lung abscess, mastitis, myositis, appendicitis, sepsis after childbirth and abortion, peritonitis, etc. Anaerobes from the genus Actinomyces cause actinomycosis in humans and animals.

Some anaerobes also perform useful functions: they contribute to the digestion and absorption of nutrients in the intestines of humans and animals (bacteria of butyric and lactic acid fermentation), participate in the cycle of substances in nature.

Methods for isolating anaerobes are based on creating anaerobic conditions (reducing the partial pressure of oxygen in the medium), for the creation of which the following methods are used: 1) removal of oxygen from the medium by pumping out air or displacement by an indifferent gas; 2) chemical absorption of oxygen using sodium hydrosulfite or pyrogallol; 3) combined mechanical and chemical removal of oxygen; 4) biological absorption of oxygen by obligate aerobic microorganisms seeded on one half of the Petri dish (Fortner method); 5) partial removal of air from the liquid nutrient medium by boiling it, adding reducing substances (glucose, thioglycolate, cysteine, pieces of fresh meat or liver) and filling the medium with vaseline oil; 6) mechanical protection from air oxygen, carried out by seeding anaerobes in a tall column of agar in thin glass tubes according to the Veillon method.

Methods for identifying isolated cultures of anaerobes - see Anaerobic infection (microbiological diagnostics).