Adaptation of microorganisms to environmental conditions. The way bacteria adapt to different temperatures turned out to be predictable. What does it look like

Bacteria are the most ancient group of organisms that currently exist on Earth. The first bacteria probably appeared more than 3.5 billion years ago and for almost a billion years were the only living creatures on our planet. Since these were the first representatives of wildlife, their body had a primitive structure.

Over time, their structure became more complex, but even today bacteria are considered the most primitive unicellular organisms. Interestingly, some bacteria still retain the primitive features of their ancient ancestors. This is observed in bacteria that live in hot sulfur springs and anoxic silts at the bottom of reservoirs.

Most bacteria are colorless. Only a few are colored purple or green. But colonies of many bacteria have bright color, which is due to the release of a colored substance into the environment or pigmentation of cells.

The discoverer of the world of bacteria was Anthony Leeuwenhoek, a Dutch naturalist of the 17th century, who first created a perfect magnifying glass microscope that magnifies objects 160-270 times.

Bacteria are classified as prokaryotes and are separated into a separate kingdom - Bacteria.

body shape

Bacteria are numerous and diverse organisms. They differ in form.

bacterium name	Bacteria shape	Bacteria image
cocci		spherical
Bacillus		rod-shaped
Vibrio		curved comma
Spirillum		Spiral
streptococci		Chain of cocci
Staphylococci		Clusters of cocci
diplococci		Two round bacteria enclosed in one slimy capsule

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, while soil bacteria can move in soil capillaries.

Habitat

Due to the simplicity of organization and unpretentiousness, bacteria are widely distributed in nature. Bacteria are found everywhere: in a drop of even the purest spring water, in grains of soil, in the air, on rocks, in polar snows, desert sands, at the bottom of the ocean, in great depth oil and even in the water of hot springs with a temperature of about 80ºС. They live on plants, fruits, in various animals and in humans in the intestines, oral cavity, on the limbs, on the surface of the body.

Bacteria are the smallest and most numerous living things. Due to their small size, they easily penetrate into any cracks, crevices, pores. Very hardy and adaptable different conditions existence. They tolerate drying, extreme cold, heating up to 90ºС, without losing viability.

There is practically no place on Earth where bacteria would not be found, but in different quantities. The living conditions of bacteria are varied. Some of them need air oxygen, others do not need it and are able to live in an oxygen-free environment.

In the air: bacteria rise to the upper atmosphere up to 30 km. and more.

Especially a lot of them in the soil. One gram of soil can contain hundreds of millions of bacteria.

In water: in the surface water layers of open reservoirs. Beneficial aquatic bacteria mineralize organic residues.

In living organisms: pathogenic bacteria enter the body from the external environment, but only under favorable conditions cause disease. Symbiotic live in the digestive organs, helping to break down and assimilate food, synthesize vitamins.

External structure

The bacterial cell is dressed in a special dense shell - the cell wall, which performs protective and supporting functions, and also gives the bacterium a permanent, characteristic shape. The cell wall of a bacterium resembles the shell of a plant cell. It is permeable: through it, nutrients freely pass into the cell, and metabolic products go out into the environment. Bacteria often develop an additional protective layer of mucus, a capsule, over the cell wall. The thickness of the capsule can be many times greater than the diameter of the cell itself, but it can be very small. The capsule is not an obligatory part of the cell, it is formed depending on the conditions in which the bacteria enter. It keeps bacteria from drying out.

On the surface of some bacteria there are long flagella (one, two or many) or short thin villi. The length of the flagella can be many times greater than the size of the body of the bacterium. Bacteria move with the help of flagella and villi.

Internal structure

Inside the bacterial cell is a dense immobile cytoplasm. It has a layered structure, there are no vacuoles, therefore various proteins(enzymes) and reserve nutrients are located in the very substance of the cytoplasm. Bacterial cells do not have a nucleus. In the central part of their cells, a substance carrying hereditary information is concentrated. Bacteria, - nucleic acid - DNA. But this substance is not framed in the nucleus.

The internal organization of a bacterial cell is complex and has its own specific features. The cytoplasm is separated from the cell wall by the cytoplasmic membrane. In the cytoplasm, the main substance, or matrix, ribosomes and a small number of membrane structures that perform a variety of functions (analogues of mitochondria, endoplasmic reticulum, Golgi apparatus) are distinguished. The cytoplasm of bacterial cells often contains granules of various shapes and sizes. The granules may be composed of compounds that serve as a source of energy and carbon. Droplets of fat are also found in the bacterial cell.

In the central part of the cell, the nuclear substance, DNA, is localized, not separated from the cytoplasm by a membrane. This is an analogue of the nucleus - the nucleoid. Nucleoid does not have a membrane, nucleolus and a set of chromosomes.

Nutrition methods

Bacteria have different ways of feeding. Among them are autotrophs and heterotrophs. Autotrophs are organisms that can independently form organic substances for their nutrition.

Plants need nitrogen, but they themselves cannot absorb nitrogen from the air. Some bacteria combine nitrogen molecules in the air with other molecules, resulting in substances available to plants.

These bacteria settle in the cells of young roots, which leads to the formation of thickenings on the roots, called nodules. Such nodules are formed on the roots of plants of the legume family and some other plants.

The roots provide the bacteria with carbohydrates, and the bacteria give the roots nitrogen-containing substances that can be taken up by the plant. Their relationship is mutually beneficial.

Plant roots secrete many organic substances (sugars, amino acids, and others) that bacteria feed on. Therefore, especially many bacteria settle in the soil layer surrounding the roots. These bacteria convert dead plant residues into substances available to the plant. This layer of soil is called the rhizosphere.

There are several hypotheses about the penetration of nodule bacteria into root tissues:

• through damage to the epidermal and cortical tissue;
• through root hairs;
• only through the young cell membrane;
• due to companion bacteria producing pectinolytic enzymes;
• due to the stimulation of the synthesis of B-indoleacetic acid from tryptophan, which is always present in the root secretions of plants.

The process of introduction of nodule bacteria into the root tissue consists of two phases:

• infection of the root hairs;
• nodule formation process.

In most cases, the invading cell actively multiplies, forms the so-called infection threads, and already in the form of such threads moves into the plant tissues. Nodule bacteria that have emerged from the infection thread continue to multiply in the host tissue.

Filled with rapidly multiplying cells of nodule bacteria, plant cells begin to intensively divide. The connection of a young nodule with the root of a leguminous plant is carried out thanks to vascular-fibrous bundles. During the period of functioning, the nodules are usually dense. By the time of the manifestation of optimal activity, the nodules acquire a pink color (due to the legoglobin pigment). Only those bacteria that contain legoglobin are capable of fixing nitrogen.

Nodule bacteria create tens and hundreds of kilograms of nitrogen fertilizers per hectare of soil.

Metabolism

Bacteria differ from each other in metabolism. For some, it goes with the participation of oxygen, for others - without its participation.

Most bacteria feed on ready-made organic substances. Only a few of them (blue-green, or cyanobacteria) are able to create organic substances from inorganic ones. They played important role in the accumulation of oxygen in the Earth's atmosphere.

Bacteria absorb substances from the outside, tear their molecules apart, assemble their shell from these parts and replenish their contents (this is how they grow), and throw unnecessary molecules out. The shell and membrane of the bacterium allows it to absorb only the right substances.

If the shell and membrane of the bacterium were completely impermeable, no substances would enter the cell. If they were permeable to all substances, the contents of the cell would mix with the medium - the solution in which the bacterium lives. For the survival of bacteria, a shell is needed that allows the necessary substances to pass through, but not those that are not needed.

The bacterium absorbs the nutrients that are near it. What happens next? If it can move independently (by moving the flagellum or pushing the mucus back), then it moves until it finds the necessary substances.

If it cannot move, then it waits until diffusion (the ability of the molecules of one substance to penetrate into the thick of the molecules of another substance) brings the necessary molecules to it.

Bacteria, together with other groups of microorganisms, perform a huge chemical job. By transforming various compounds, they receive the energy and nutrients necessary for their vital activity. Metabolic processes, ways of obtaining energy and the need for materials to build the substances of their body in bacteria are diverse.

Other bacteria satisfy all the needs for carbon necessary for the synthesis of organic substances of the body at the expense of inorganic compounds. They are called autotrophs. Autotrophic bacteria are able to synthesize organic substances from inorganic ones. Among them are distinguished:

Chemosynthesis

The use of radiant energy is the most important, but not the only way to create organic matter from carbon dioxide and water. Bacteria are known that use not sunlight, but energy as an energy source for such synthesis. chemical bonds occurring in the cells of organisms during the oxidation of certain inorganic compounds - hydrogen sulfide, sulfur, ammonia, hydrogen, nitric acid, ferrous compounds of iron and manganese. They use the organic matter formed using this chemical energy to build the cells of their body. Therefore, this process is called chemosynthesis.

The most important group of chemosynthetic microorganisms are nitrifying bacteria. These bacteria live in the soil and carry out the oxidation of ammonia, formed during the decay of organic residues, to nitric acid. The latter, reacts with mineral compounds of the soil, turns into salts of nitric acid. This process takes place in two phases.

Iron bacteria convert ferrous iron to oxide. The formed iron hydroxide settles and forms the so-called swamp iron ore.

Some microorganisms exist due to the oxidation of molecular hydrogen, thereby providing an autotrophic way of nutrition.

A characteristic feature of hydrogen bacteria is the ability to switch to a heterotrophic lifestyle when provided with organic compounds and in the absence of hydrogen.

Thus, chemoautotrophs are typical autotrophs, since they independently synthesize the necessary organic compounds from inorganic substances, and do not take them into ready-made from other organisms, like heterotrophs. Chemoautotrophic bacteria differ from phototrophic plants in their complete independence from light as an energy source.

bacterial photosynthesis

Some pigment-containing sulfur bacteria (purple, green), containing specific pigments - bacteriochlorophylls, are able to absorb solar energy, with the help of which hydrogen sulfide is split in their organisms and gives hydrogen atoms to restore the corresponding compounds. This process has much in common with photosynthesis and differs only in that in purple and green bacteria, hydrogen sulfide (occasionally carboxylic acids) is a hydrogen donor, and in green plants it is water. In those and others, the splitting and transfer of hydrogen is carried out due to the energy of absorbed solar rays.

Such bacterial photosynthesis, which occurs without the release of oxygen, is called photoreduction. The photoreduction of carbon dioxide is associated with the transfer of hydrogen not from water, but from hydrogen sulfide:

6CO 2 + 12H 2 S + hv → C6H 12 O 6 + 12S \u003d 6H 2 O

The biological significance of chemosynthesis and bacterial photosynthesis on a planetary scale is relatively small. Only chemosynthetic bacteria play a significant role in the sulfur cycle in nature. Absorbed by green plants in the form of salts of sulfuric acid, sulfur is restored and becomes part of protein molecules. Further, when dead plant and animal remains are destroyed by putrefactive bacteria, sulfur is released in the form of hydrogen sulfide, which is oxidized by sulfur bacteria to free sulfur (or sulfuric acid), which forms sulfites available for plants in the soil. Chemo- and photoautotrophic bacteria are essential in the cycle of nitrogen and sulfur.

sporulation

Spores form inside the bacterial cell. In the process of spore formation bacterial cell undergoes a series of biochemical processes. The amount of free water in it decreases, enzymatic activity decreases. This ensures the resistance of spores to adverse environmental conditions (high temperature, high salt concentration, drying, etc.). Spore formation is characteristic of only a small group of bacteria.

Disputes are not a mandatory stage life cycle bacteria. Sporulation begins only with a lack of nutrients or the accumulation of metabolic products. Bacteria in the form of spores can remain dormant for a long time. Bacterial spores withstand prolonged boiling and very long freezing. When favorable conditions occur, the dispute germinates and becomes viable. Bacterial spores are adaptations for survival in adverse conditions.

reproduction

Bacteria reproduce by dividing one cell into two. Having reached a certain size, the bacterium divides into two identical bacteria. Then each of them begins to feed, grows, divides, and so on.

After elongation of the cell, a transverse septum is gradually formed, and then the daughter cells diverge; in many bacteria, under certain conditions, cells after division remain connected in characteristic groups. In this case, depending on the direction of the division plane and the number of divisions, different forms arise. Reproduction by budding occurs in bacteria as an exception.

Under favorable conditions, cell division in many bacteria occurs every 20-30 minutes. With such rapid reproduction, the offspring of one bacterium in 5 days is able to form a mass that can fill all the seas and oceans. A simple calculation shows that 72 generations (720,000,000,000,000,000,000 cells) can be formed per day. If translated into weight - 4720 tons. However, this does not happen in nature, since most bacteria quickly die under the influence of sunlight, drying, lack of food, heating up to 65-100ºС, as a result of the struggle between species, etc.

The bacterium (1), having absorbed enough food, increases in size (2) and begins to prepare for reproduction (cell division). Its DNA (in a bacterium, the DNA molecule is closed in a ring) doubles (the bacterium produces a copy of this molecule). Both DNA molecules (3.4) appear to be attached to the bacterial wall and, when elongated, the bacteria diverge to the sides (5.6). First, the nucleotide divides, then the cytoplasm.

After the divergence of two DNA molecules on bacteria, a constriction appears, which gradually divides the body of the bacterium into two parts, each of which contains a DNA molecule (7).

It happens (in hay bacillus), two bacteria stick together, and a bridge is formed between them (1,2).

DNA is transported from one bacterium to another via the jumper (3). Once in one bacterium, DNA molecules intertwine, stick together in some places (4), after which they exchange sections (5).

The role of bacteria in nature

Circulation

Bacteria are the most important link in the general circulation of substances in nature. Plants create complex organic substances from carbon dioxide, water and soil mineral salts. These substances return to the soil with dead fungi, plants and animal corpses. Bacteria decompose complex substances into simple ones, which are reused by plants.

Bacteria destroy the complex organic matter of dead plants and animal corpses, excretions of living organisms and various wastes. Feeding on these organic substances, saprophytic decay bacteria turn them into humus. These are the kind of orderlies of our planet. Thus, bacteria are actively involved in the cycle of substances in nature.

soil formation

Because bacteria are ubiquitous and found in huge number, they largely determine the various processes occurring in nature. In autumn, the leaves of trees and shrubs fall, die above-ground shoots herbs, old branches fall, from time to time the trunks of old trees fall. All this gradually turns into humus. In 1 cm 3. The surface layer of forest soil contains hundreds of millions of saprophytic soil bacteria of several species. These bacteria convert humus into various minerals that can be absorbed from the soil by plant roots.

Some soil bacteria are able to absorb nitrogen from the air, using it in life processes. These nitrogen-fixing bacteria live on their own or take up residence in the roots of leguminous plants. Having penetrated into the roots of legumes, these bacteria cause the growth of root cells and the formation of nodules on them.

These bacteria release nitrogen compounds that plants use. Bacteria obtain carbohydrates and mineral salts from plants. Thus, there is a close relationship between the leguminous plant and root nodule bacteria, which is useful for both one and the other organism. This phenomenon is called symbiosis.

Thanks to their symbiosis with nodule bacteria, legumes enrich the soil with nitrogen, helping to increase yields.

Distribution in nature

Microorganisms are ubiquitous. The only exceptions are the craters of active volcanoes and small areas in the epicenters of exploded volcanoes. atomic bombs. Neither the low temperatures of the Antarctic, nor the boiling jets of geysers, nor saturated salt solutions in salt pools, nor the strong insolation of mountain peaks, nor the harsh radiation of nuclear reactors interfere with the existence and development of microflora. All living beings constantly interact with microorganisms, being often not only their storages, but also distributors. Microorganisms are the natives of our planet, actively developing the most incredible natural substrates.

Soil microflora

The number of bacteria in the soil is extremely large - hundreds of millions and billions of individuals in 1 gram. They are much more abundant in soil than in water and air. The total number of bacteria in soils varies. The number of bacteria depends on the type of soil, their condition, the depth of the layers.

On the surface of soil particles, microorganisms are located in small microcolonies (20-100 cells each). Often they develop in the thicknesses of clots of organic matter, on living and dying plant roots, in thin capillaries and inside lumps.

Soil microflora is very diverse. Different physiological groups of bacteria are found here: putrefactive, nitrifying, nitrogen-fixing, sulfur bacteria, etc. among them there are aerobes and anaerobes, spore and non-spore forms. Microflora is one of the factors of soil formation.

The area of ​​development of microorganisms in the soil is the zone adjacent to the roots of living plants. It is called the rhizosphere, and the totality of microorganisms contained in it is called the rhizosphere microflora.

Microflora of reservoirs

Water - natural environment where microorganisms grow in abundance. Most of them enter the water from the soil. A factor that determines the number of bacteria in water, the presence of nutrients in it. The purest waters are artesian wells and spring. Open reservoirs and rivers are very rich in bacteria. The largest number bacteria is found in the surface layers of the water, closer to the shore. With increasing distance from the coast and increasing depth, the number of bacteria decreases.

Pure water contains 100-200 bacteria per 1 ml, while contaminated water contains 100-300 thousand or more. There are many bacteria in the bottom silt, especially in the surface layer, where the bacteria form a film. There are a lot of sulfur and iron bacteria in this film, which oxidize hydrogen sulfide to sulfuric acid and thereby prevent fish from dying. There are more spore-bearing forms in the silt, while non-spore-bearing forms predominate in the water.

By species composition the microflora of water is similar to the microflora of soil, but there are also specific forms. Destroying various wastes that have fallen into the water, microorganisms gradually carry out the so-called biological purification of water.

Air microflora

Air microflora is less numerous than soil and water microflora. Bacteria rise into the air with dust, can stay there for a while, and then settle to the surface of the earth and die from lack of nutrition or under the influence of ultraviolet rays. The number of microorganisms in the air depends on the geographic area, terrain, season, dust pollution, etc. Each speck of dust is a carrier of microorganisms. Most bacteria in the air over industrial enterprises. Air countryside cleaner. The cleanest air is over forests, mountains, snowy spaces. The upper layers of the air contain fewer germs. In the air microflora there are many pigmented and spore-bearing bacteria that are more resistant than others to ultraviolet rays.

Microflora of the human body

The body of a person, even a completely healthy one, is always a carrier of microflora. When the human body comes into contact with air and soil, a variety of microorganisms, including pathogens (tetanus bacilli, gas gangrene, etc.), settle on clothing and skin. The exposed parts of the human body are most frequently contaminated. E. coli, staphylococci are found on the hands. There are over 100 types of microbes in the oral cavity. The mouth, with its temperature, humidity, nutrient residues, is an excellent environment for the development of microorganisms.

The stomach has an acidic reaction, so the bulk of microorganisms in it die. Starting from the small intestine, the reaction becomes alkaline, i.e. favorable for microbes. The microflora in the large intestine is very diverse. Each adult excretes about 18 billion bacteria daily with excrement, i.e. more individuals than people on the globe.

Internal organs that are not connected to the external environment (brain, heart, liver, bladder, etc.) are usually free from microbes. Microbes enter these organs only during illness.

Bacteria in the cycling

Microorganisms in general and bacteria in particular play an important role in the biologically important cycles of substances on Earth, carrying out chemical transformations that are completely inaccessible to either plants or animals. Various stages of the cycle of elements are carried out by organisms different type. The existence of each separate group organisms depends on chemical transformation elements carried out by other groups.

nitrogen cycle

The cyclic transformation of nitrogenous compounds plays a primary role in the supply necessary forms nitrogen of different nutritional needs of organisms of the biosphere. Over 90% of total nitrogen fixation is due to the metabolic activity of certain bacteria.

The carbon cycle

The biological conversion of organic carbon into carbon dioxide, accompanied by the reduction of molecular oxygen, requires the joint metabolic activity of various microorganisms. Many aerobic bacteria carry out the complete oxidation of organic substances. Under aerobic conditions, organic compounds are initially broken down by fermentation, and organic fermentation end products are further oxidized by anaerobic respiration if inorganic hydrogen acceptors (nitrate, sulfate, or CO2) are present.

Sulfur cycle

For living organisms, sulfur is available mainly in the form of soluble sulfates or reduced organic sulfur compounds.

The iron cycle

In some water bodies, fresh water contain high concentrations of reduced iron salts. In such places, a specific bacterial microflora develops - iron bacteria, which oxidize reduced iron. They are involved in the formation of swamps iron ore and water sources rich in iron salts.

Bacteria are the most ancient organisms, appearing about 3.5 billion years ago in the Archaean. For about 2.5 billion years, they dominated the Earth, forming the biosphere, and participated in the formation of an oxygen atmosphere.

Bacteria are one of the most simply arranged living organisms (except for viruses). They are believed to be the first organisms to appear on Earth.

Tests

666-01. How is a bacterial spore different from a free bacterium?
A) The spore has a denser shell than a free bacterium.
B) A spore is a multicellular formation, and a free bacterium is unicellular.
C) The spore is less durable than the free bacterium.
D) The spore feeds autotrophically, while the free bacterium feeds heterotrophically.

Answer

Answer

666-03. Specify a case of symbiosis of a bacterium with another organism.
A) cholera and human vibrio
B) salmonella and chicken
B) anthrax bacillus and sheep
D) E. coli and man

Answer

666-04. Nodule bacteria supply moth plants
A) organic matter from dead plants
B) nitrogen salts
B) nucleic acids
D) carbohydrates

Answer

666-05. Unfavorable conditions for the life of bacteria are created when
A) sauerkraut
B) canning mushrooms
B) making kefir
D) silo laying

Answer

Answer

666-07. Anthrax bacteria can exist for a long time in animal burial grounds in the form of
A) dispute
B) cyst
B) living cells
D) zoospore

Answer

Answer

666-09. What is characteristic of saprotrophic bacteria?
A) exist by feeding on the tissues of living organisms

C) use organic substances from the secretions of living organisms

Answer

666-10. Bacteria exist on Earth for millions of years along with highly organized organisms, since
A) feed on ready-made organic substances
B) when adverse conditions occur, they form disputes
B) participate in the cycle of substances in nature
D) have a simple structure and microscopic dimensions

Answer

666-11. Which of the following statements is correct?
A) bacteria reproduce by meiosis
B) all bacteria are heterotrophs
B) bacteria adapt well to environmental conditions
D) some bacteria are eukaryotic organisms

Answer

666-12. The similarity of the vital activity of cyanobacteria and flowering plants is manifested in the ability to
A) heterotrophic nutrition
B) autotrophic nutrition
B) the formation of seeds
D) double fertilization

Answer

666-13. Decay bacteria living in the soil
A) form organic compounds from inorganic compounds
B) feed on organic matter of living organisms
C) contribute to the neutralization of poisons in the soil
D) decompose the dead remains of plants and animals to humus

Answer

666-14. What are the characteristics of putrefactive bacteria?
A) use ready-made organic substances of living organisms
B) synthesize organic substances from inorganic, using the energy of the sun
B) use organic matter of dead organisms
D) synthesize organic substances from inorganic substances, using the energy of chemical reactions

Answer

666-15. What bacteria are considered the "orderlies" of the planet?
A) acetic acid
B) nodule
B) decay
D) lactic acid

Answer

666-16. Dysentery amoeba, ciliate shoe, green euglena belong to the same subkingdom because they have
BUT) overall plan buildings
B) similar type of food
C) the same methods of reproduction
D) general habitat

Answer

666-17. What physiological process in unicellular animals is associated with the absorption of gases by the cell?
A) food
B) selection
B) reproduction
D) breathing

Biological adaptation (from Latin adaptatio - adaptation) - the adaptation of a microorganism to external conditions in the process of evolution, including morphophysiological and behavioral components. Adaptation can ensure survival in a particular habitat, resistance to abiotic and biological factors, as well as success in competition with other species, populations, and individuals. Each species has its own ability to adapt, limited by physiology (individual adaptation).

Disadaptation - any violation of adaptation, adaptation of the body to constantly changing conditions of the external or internal environment. The state of dynamic discrepancy between a living organism and the environment, leading to a violation of physiological functioning, a change in behavior, the development of pathological processes A complete discrepancy between the organism and the external conditions of its existence is incompatible with life. The degree of disadaptation is characterized by the level of disorganization of the functional systems of the body. Depending on the nature of functioning, there are two forms of maladaptation: - non-pathological: maintenance of homeostasis is possible with a regime of enhanced, but "normal" physiological functioning; – pathological: maintenance of homeostasis is possible only in the transition to pathological functioning.

Adaptations of species within the same biocenosis are often closely related to each other. If the adaptation process in any species is not in an equilibrium state, then the entire biocenosis can evolve (sometimes with negative consequences) even in stable environmental conditions.

The main content of adaptation, according to T. Pilate, is the internal processes in the system that ensure the preservation of its external functions in relation to the environment. If the structure of the system ensures its normal functioning under the given environmental conditions, then such a system should be considered adapted to these conditions. At this stage, dynamic equilibrium is established.

Examples of adaptation: in freshwater protozoa, the osmotic concentration of protoplasm is higher than the concentration of the surrounding water. When water is absorbed in it, constant desalination occurs. The disturbed osmotic balance is regulated by the activity of the contractile vacuole, which removes excess water from the body. Some protozoa are able, however, to adapt to existence in more salty and even sea water. At the same time, the activity of the contractile vacuole in them slows down and may even stop completely, since under these conditions the removal of water from the body would lead to an increase in the relative concentration of ions in the protoplasm and, in connection with this, to a violation of the osmotic balance in it. Thus, in this case, the mechanism of adaptation is reduced to a direct physical and chemical reaction of the protoplasm. In other cases, the adaptation mechanism seems to be more complex and cannot always be immediately decomposed into elementary factors. Such, for example, are the adaptation of animals to temperature conditions (elongation of the fur of mammals under the influence of cold), to the phenomena of radiant energy (plant phototropism); discoloration of the skin of cold-blooded animals, due to the reaction of pigment cells; seasonal dimorphism in the coloration of birds and mammals; a change in their color depending on climatic and geographical conditions, etc. However, here, too, the mechanism of adaptation can ultimately be reduced to the physicochemical reactions of protoplasm. The phenomena of adaptation are closely connected with the evolution of microorganisms and represent one of the most significant factors of acclimatization, the struggle for existence and mimicry.

Adaptation of microorganisms, accommodation of microorganisms, their adaptation to the environment. Their structure, physiological properties and chemical composition depend both on the hereditary properties of a given species and on environmental influences. The latter cause the microorganism to change. Until recently, these changes were considered random and, according to the teachings of Conn, of little importance for the main features of the microorganism, which were recognized as unshakable. However, over time, at first timidly, and then more and more decisively, the doctrine of the variability of microorganisms as a biological factor was put forward, and at present, changes in microorganisms are no longer considered only random, but are recognized as deeper. The nature of the variability of a microorganism depends on two factors: on the individual species resistance of a given microorganism and on the depth, scope and strength of the environmental impact. Some types of microorganisms, such as the acid-resistant group, diphtheria and fungal forms, change less and adapt worse, while the enteric-typhoid, capsular, coccal, anaerobic groups are more easily subject to changes. The adaptability of microorganisms primarily affects their relationship to oxygen and ambient temperature. It is known that anaerobes can be accustomed both to free oxygen and vice versa. The same must be said about the attitude to the ambient temperature, as well as to the reaction of the environment, to the action of light and the chemical composition of the nutrient material. One condition must be met for this adaptation to occur: gradual exposure to new factors. The slower and more gradually the new conditions act, the easier and more perfectly the microorganism adapts. This fixture comes with various directions. Environmental conditions cause the microorganism to become less demanding in its physiological functions, limit them to a minimum and move into the stage of anabiosis (“latent microbiism”), for which it forms spores and is surrounded by impenetrable mucous, calcareous and connective tissue capsules (cocci, tubes, etc.). sticks, etc.); or microorganisms undergo morphological changes, losing whole organs and parts that are particularly sensitive to normal conditions (for example, trypanosomes, becoming accustomed to arsenic, lose blepharoblasts (Verbitsky)), and thus new races of microorganisms are obtained. The formation of new races with new properties is especially easy when a microorganism encounters new chemicals in an organism in which it is accustomed to reproduce freely. When in such an environment appear harmful substances , some of the microorganisms die, but the most resistant individuals survive and give rise to the so-called "resistant" or "stubborn" races (Enrlich). Such resistance has been proven in relation to various chemical compounds and alkaloids (arsenic, alcohol, quinine). The adaptability of microorganisms can also go in the opposite direction - towards enhancing their viability and acquiring greater activity. Thus, a low virulent microorganism, under the influence of a weakening of the body, begins to multiply rapidly and produce toxins that it did not have or had little before. An example here is the numerous cases of so-called endogenous infections, when pneumococcus, under the influence of a cold, causes pneumonia or Bact. coli, under the influence of an error in the diet, causes a dysentery-like disease. This "activation" of the microorganism is nothing but its adaptation to new conditions. The phenomena of adaptation are especially well studied and numerous where the microorganism meets with an immune organism or immune environments. In addition to the capsules mentioned above, which serve as a protective layer for the microbe from the external environment, the microorganism begins to produce aggressins, which make it less accessible to phagocytes. The adaptability of microorganisms goes so far that they can become resistant even to immune sera. Bordet showed as early as 1895 how Vibrio cholerae can be accustomed to bacteriolytic serum. A number of authors have proved the possibility of accustoming agglutinating microorganisms to the fact that they cease to agglutinate. Conversely, non-aglutinable microorganisms can be converted into agglutinating ones, for example, by passing through the body of animals and even by simple transfers from medium to medium. Rebuilding their morphological and physiological features, microorganisms, depending on the soil on which they live, and depending on other microorganisms that multiply next to it, can acquire the features inherent in a neighbor and turn into a so-called "paramicrobe". Such a microorganism, as Rosenow proved, can acquire new properties acquired by cohabitation with a pathogenic microorganism and retain them for quite a long time by inheritance. So, for example, streptococcus isolated from meningitis caused by diplococcus Weichselbaum'a acquires the ability to give meningitis. It turns out, as it were, an imitation of another pathogen. This imitation is expressed either in the ability to cause the same disease or in the acquisition of new antigenic properties. Thus, a proteus living in the body of a typhus patient begins to agglutinate with the patient's serum, although it is not the causative agent of the disease. From all the facts presented, it is clear which great importance have phenomena of adaptation of microorganisms for pathology and epidemiology.

The evolution of bacteria and its medical significance. Microorganisms on Earth arose about three billion years before the appearance of man. In 1822, E. Darwin proposed the theory of evolution, and 100 years later, the Russian biochemist A. Oparin (1920) proposed the theory of the emergence of biological life. Bacteria play an important role in this system. The first self-replicating forms of biological life surrounded by a membrane (protobionts) were incapable of photosynthesis and obtained energy through simple, one-step abiogenic oxidative reactions. This continued for about 1.0 billion years. The energy (electrochemical, thermal, photochemical) generated in these reactions was stored in certain molecules and used to carry out primitive processes. The formation of primary molecules and reactions marked the beginning of metabolic processes - anabolism and catabolism. The transition from protocell to prokaryotic cell occurred between 2.5-3 billion years ago. There was no oxygen in the atmosphere of the planet and the primary prokaryotes were anaerobes. The autotrophic pathway of CO 2 fixation was the basis of primary productivity on the planet. The change from a reducing atmosphere to an oxygen atmosphere occurred between the Middle and Late Precambrian (2.8 billion years ago). For comparison, the oxygen content in the planet's atmosphere 800 million years ago was about 1%, 400 million years ago it was already 10%, and now it is 21%. As the composition of the atmosphere changed, facultative phototrophic and heterotrophic anaerobes began to form, later aerobic bacteria arose.

Bacteria were not only the primary accumulators of genes, but the object of their evolutionary improvement. The rate of evolution is the number of mutations per 100 amino acids of a certain protein molecule within 100 million years. It varies widely. This is the basis for the concept of molecular clock, declaring that mutations gradually accumulate in the genome and form a new sequence for the further divergence of the species in a linear time period of evolution. The diagram presented in Fig.3. allows you to display the evolution of certain groups of bacteria and approximately establish the evolutionary time when a particular species (genus) diverged from common ancestor.

The rate of evolution is constant and depends on many factors - the rate of metabolic processes, generation time, information flow and selective pressure. For example, the divergence of the genus Salmonella and the genus Escherichia coli from a common ancestor occurred approximately 100-140 million years ago. Bacterial genomes have evolved over 50 billion generations, accumulating mutations and acquiring new genetic information through horizontal gene transfer without significant rearrangement of ancestral genes. During the year, the Salmonella genome acquired approximately 16 kb / million of foreign genetic information. years, and E. coli - 22 kb / million years. Currently, their genomes differ by 25%. A significant part of the genome was acquired by horizontal transfer. In general, the bacterial genome varies in size from 0.6 to 9.4 Mb of information (3 to 5 Mb on average). Some bacteria have two chromosomes (Leptospira interrogans serovar icterohemorrahgiae, Brucellae melitensis). The progressive evolution of bacteria took place in several interrelated directions - metabolic, morphological (structural-molecular), and ecological. In nature, there is a huge variety of microorganisms, of which no more than 5-7% are currently known, and bacteria cultivated under artificial conditions make up about 1%. This means that we are just beginning to get to know the world of microbes.

Genome sequencing strategies. Each base pair of the genome is one bit of information. For example, the genome of Haemophilus influenzae contains 1,830,137 and the genome of Escherichia coli contains 4,639,221 bits of information. Comparative aspects of bacterial genome sequencing make it possible to determine the presence of common genes and regulatory mechanisms, to establish evolutionary intra- and interspecies relationships, and are the basis of structural and evolutionary genomics. Mathematical analysis of the genomes of microorganisms is engaged in new science- bioinformatics. The subject of research is the sequencing of fragments or complete genomes of bacteria using the developed computer programs and databases of information on nucleic acids and proteins.

Based on the analysis of the structure of genomes (sequencing), 36-40 large taxa (divisions) were formed. The members of each of them have a common ancestor, which at a certain stage diverged from another predecessor taxon. Some of the departments include more species of known bacteria than others. This usually refers to those that are well cultivated in the laboratory. The largest number of bacterial species (from 40 to 80%) was described among the taxa of Proteobacteria, Actinobacteria, Gram-positive bacteria with a low content of G+C. At the same time, in some departments cultivated representatives of bacteria are unknown. It should be noted that out of 36-40 divisions of the kingdom Bacteria, only representatives of 7 large taxa are capable of causing diseases in humans. The specialization and adaptation of these bacteria to the animal organism led to the formation of blocks of genes that control pathogenicity factors (pathogenicity islands). They can be localized in the chromosome, plasmids and, possibly, in bacterial phages. Establishing the direction and order of the evolution of microorganisms based on the variability of their genomes is a promising direction in molecular epidemiology.

In addition to genotypic, there is modification variability , which is considered as a response to a change in environmental conditions and is observed as long as the factor causing these changes is in effect. Modification variability(also called phenotypic variability) manifests itself at the phenotype level and does not affect the genotype.

Phenotypic variability is manifested in the vast majority of individuals in a population, while with mutational variability, a change in the genotype occurs only in single cells.

Modification is the result of the plasticity of cellular metabolism, leading to the phenotypic manifestation of "silent" genes under specific conditions. Thus, modification changes take place within the framework of an unchanged cell genotype.

There are several manifestations of modification changes. Most famous adaptive modifications , i.e. . non-hereditary changes that are beneficial to an organism and help it survive in a changed environment.

The reasons for adaptive modifications lie in the mechanisms of regulation of the action of genes. An example of this is the adaptation of bacterial cells E. coli to lactose as a new substrate: under these conditions, inducible enzymes begin to be synthesized, i.e., the phenotypic manifestation of genes that are “silent” in the absence of lactose in the environment occurs.

Found in a number of bacteria universal adaptive response in response to various stressful influences (high and low temperatures, a sharp shift in pH, etc.). In this case, the adaptive response is manifested in the intensive synthesis of a small group of similar proteins, which are called heat shock proteins , and the phenomenon heat shock syndrome . Under stressful effects on a bacterial cell, the synthesis of conventional proteins is inhibited in it, but the synthesis of a small group of proteins is induced, the functions of which are to counteract stress by protecting the most important cellular structures, primarily the nucleoid and membranes. It is believed that adaptive modifications expand the ability of an organism to survive and reproduce in a wider range of environmental conditions. The resulting modifications can be relatively stable they can persist for several generations or, conversely, very labile.

However, not all modifications can be considered as adaptive. With intensive exposure to many agents, there are observed non-inherited changes, random in relation to the influence that caused them. The reasons for the appearance of such phenotypically altered cells are associated with errors in the translation process caused by these agents.

Meaning of adaptive modifications:

- make a certain contribution to the process of evolution;

- expand the ability of the organism to survive and reproduce in a wider range of environmental conditions. The hereditary changes arising under these conditions are picked up by natural selection and in this way there is a more active development of new ecological niches and more effective adaptability to them is achieved.

5 TOLERANCE OF MICROORGANISMS TO ENVIRONMENTAL FACTORS

The development and vital activity of microorganisms are closely connected with the environment. The manifestation of their activity depends on changes or features of this environment.

Each type of microorganism is able to grow, develop and reproduce under external conditions that reflect their level of tolerance.

Environmental factors of the environment are numerous and diverse. They are usually divided into physical, chemical and biological.

Microorganisms are better adapted to extreme physical and chemical environmental factors than animals and plants. Some bacteria remain viable at temperatures up to +104 ° C, in the pH range from 1 to 13, pressure from 0 to 1400 atm. antiseptics, antibiotics, disinfectants. At the same time, for each species there are hereditarily determined optimal levels and critical limits of microbial tolerance to physical, chemical, and biological factors.

Tolerance to physical environmental factors

The physical factors of the external environment that positively or negatively affect the vital activity of microorganisms include: the humidity of the environment, the concentration of dissolved substances in it and its osmotic pressure, temperature, sunlight and various forms radiant energy.

Humidity of the environment. Some types of microbes are very sensitive to lack of moisture. For example, nitrifying and acetic acid bacteria quickly die off after drying. Others, on the contrary, can be preserved in a dried state for several months and even years (staphylococcus, lactic acid bacteria, yeast). Spores of bacteria and mold fungi are especially resistant to drying. They can be preserved in a dried state for decades. Drying in a vacuum at a low temperature, followed by storage in an airless environment, preserves the vital activity of microbes for a long time (lyophilic). This method is widely used for long-term storage of microbial cultures. So, some pathogenic bacteria (cocci) were preserved in similar conditions for 25, and mycobacteria - for 17 years.

In the soil, various groups of microorganisms develop most intensively at a moisture content close to 60% of the total moisture capacity.

The most moisture-loving soil bacteria include nitrogen-fixing bacteria (azotobacter and nodule bacteria). When the soil dries out, microbiological activity decreases or is completely suppressed. The inability of microorganisms to develop in conditions of insufficient humidity is used to protect food and feed from spoilage by drying. Drying is subjected to meat, fish, vegetables, fruits, milk and other products, as well as hay.

The concentration of substances dissolved in the medium. Under natural conditions, microorganisms live in solutions with different concentrations of dissolved substances, and, consequently, with different osmotic pressure.

An increase in the concentration of salts in the environment above the optimum disrupts the normal metabolism between the cell and the environment. In this case, water leaves the cell, the cytoplasm moves away from the cell membrane (plasmolysis), and the supply of nutrients to the cell stops. In this state, microorganisms die rather quickly and only a few are able to persist for a long time. So, there are bacteria that have adapted to high salt concentrations (about 29%). These bacteria are called halophilic("loving" salt).

The destructive effect of high concentrations of salts on microorganisms has also found application in practical human activities. It underlies the preservation of many food products (meat, fish) in strong salt solutions. Most putrefactive bacteria stop developing already at 5-10% NaCl concentration in the medium (Proteus vulgaris, bacillus mesentericus). However, to obtain more reliable results, more concentrated salt solutions are used - 20-30%.

To create a high osmotic pressure in a liquid, in addition to sodium chloride, sugars are widely used, but in concentrations exceeding 70%.

Temperature. The temperature of the environment is one of the most important environmental factors affecting the life of microbes. Each type of microorganisms can develop only within certain temperature limits.

In relation to temperature, microorganisms are usually divided into three groups: psychrophilic, mesophilic and thermophilic.

To psychrophilic(Greek psichrio - cold, phileo - love) include microorganisms that have adapted to development at low temperatures. These are mold fungi, luminous bacteria, bacteria of cold reservoirs, glaciers, etc. For them, the minimum temperature is from 0 to 10 ° C, the optimum is about 10 ° C and the maximum is 20-30 ° C. Some species are able to grow even at temperatures below 0 ° C.

In general, microorganisms are insensitive to low temperatures. A number of researchers have proven that bacteria remain viable after being treated for several hours with liquid air (-182, -100 °C) or even liquid hydrogen (-252 °C). Low temperatures stop the vital activity of microorganisms, therefore, they prevent spoilage of chilled meat, fish, butter, milk and other products. Repeated freezing after thawing has a detrimental effect on microbes. Psychrophilic bacteria do not form spores.

mesophilic bacteria(Greek inesos - medium) develop at medium temperatures. These include most saprophytes and all pathogenic microbes.

For them, the temperature minimum lies within 0-10 ° C, the optimum is at 25-35 ° C and the maximum is at 40-50 ° C.

thermophilic bacteria(Greek termos - warm) develop at a relatively high temperature. The temperature minimum for them is about 30 ° C, the optimum is 50-60 ° C, the maximum is 70-80 ° C.

Thermophilic microorganisms are common in hot mineral waters and take an active part in the processes of self-heating of manure, silage, wet grain.

High temperatures cause the death of microbial cells as a result of coagulation (coagulation) of cytoplasmic proteins and inactivation of enzymes. Most sporeless bacteria die when heated to 60-70 °C for 15-30 minutes, and when heated to 80-100 °C in a few seconds to 1-3 minutes. In a humid environment, bacteria at high temperatures die faster than in a dry one, since steam promotes rapid protein coagulation. Spores of many bacteria withstand heating up to 100 ° C for several hours. Even the most resistant spores in a humid environment at 120 ° C die after 20-30 minutes, and under the action of dry heat (160-170 ° C.) - after 1-2 hours.

Two methods of destroying bacteria are based on the destructive effect of high temperatures: pasteurization and sterilization.

During pasteurization, the liquid is heated to 60-70 °C for 20-30 minutes or to 70-80 °C for 6-10 minutes, while only vegetative forms of bacteria die. Pasteurization is mainly used to preserve milk, wine, caviar, fruit juices and some other products.

Sterilization means the release of any object or substance from all living beings. This is achieved by heating to 100–130 °C for 20–40 min.

The influence of light. Direct sunlight kills almost all types of bacteria, with the exception of purple and photo-bacteria. Under the influence of direct sunlight, bacteria die in a few minutes or hours.

The biological effect of sunlight on microbes is due to the ultraviolet rays contained in it. After entering the cell, they are adsorbed by vital parts, proteins and nucleic acids, causing photochemical and oxidative processes that have a detrimental effect on microorganisms. Ultraviolet rays kill in a few minutes both vegetative forms and spores.

Biologically, the most interesting are ultraviolet rays with a wavelength of 280 to 230 nm. They have a pronounced bacteriostatic and bactericidal action. Depending on the dose of radiation and the type of microorganism, the effect of ultraviolet rays can be lethal or mutagenic.

Lamps emitting ultraviolet rays with a wavelength of 254 nm are widely used for sterilization of dishes, air disinfection in hospitals and operating rooms, in schools, in the fight against weevil that affects grain. Ultraviolet rays are also used to sterilize water, milk, materials that are destroyed by high temperatures.

The influence of radiation, x-ray radiation and electricity. Rays of radium and x-rays in small doses and with a short action stimulate the reproduction of certain microbes, while in large doses they kill them. High frequency electric current leads to the death of microorganisms. Especially strong action they are subjected to ultra-high frequency currents.

Influence of mechanical shocks and high pressures. Mechanical influences (strong and frequent shocks) destroy most microbes. Shaking in a shuttel apparatus with sand or glass beads dramatically reduces the number of viable bacteria. Self-purification of water bodies from microorganisms is partly due to the movement of water in rivers and streams. High pressures have little effect on microorganisms, certain types of bacteria can normally live and multiply in the seas at a depth of 9 km, where the pressure reaches 9 × 10 4 kPa. Some types of yeast, mold fungi and bacteria tolerate pressure and 3×10 5 kPa.

Tolerance to chemical environmental factors

The chemical factors influencing the vital activity of microorganisms include: the composition and reaction of the medium, the redox conditions of the medium.

The composition of the environment. Chemical compounds can be beneficial to microorganisms and be used as nutrients or unfavorable - anti-microbial (bactericidal) that inhibit or kill microorganisms. Weak solutions enhance the vital activity of microbes. Stronger solutions kill microorganisms only in the vegetative stage, very concentrated solutions also destroy spores. The sensitivity of different microbes to the same chemical compound is not the same. Some substances have a harmful effect on some groups of microorganisms and are harmless to others.

Of the inorganic substances, salts of heavy metals (mercury, copper, silver) are most toxic to microorganisms. At their concentration of 1:1000, most bacteria die within a few minutes. Chlorine, iodine, hydrogen peroxide, potassium permanganate have a bactericidal effect. Of the mineral acids, sulfurous, boric and some other acids have these properties.

Strong poisons for microbes are phenol (carbolic acid), creosol, formalin. To varying degrees, alcohols and some organic acids (salicylic, butyric, acetic, benzoic) are toxic.

Smoking of meat and fish is based on the detrimental effect of antiseptics on bacteria, during which the product is saturated with smoke containing volatile compounds, in particular formaldehyde, phenols, and resins.

The reaction of the environment. The reaction of the environment is a significant chemical factor affecting the vital activity of microorganisms. The pH value for a neutral medium is 7.0, for acidic - 0-6.0 and alkaline - 8.0-14.0. The attitude of microbes to the reaction of the environment is very diverse. If some can develop over a wide range of pH values, then for the development of other microorganisms, fluctuations in pH should be insignificant.

For many molds and yeasts, the most favorable environment is pH 3.0-6.0; most bacteria develop better in a neutral or slightly alkaline medium (7.0-7.5). A very acidic reaction to bacteria is detrimental.

An exception is bacteria that themselves form acid (acetic acid, lactic acid, citric acid and butyric acid).

Microorganisms living in soil or water bodies encounter significant pH fluctuations, so they have adapted to a wide range of pH values. Conversely, pathogenic microorganisms living in the human or animal body can thrive in a relatively narrow pH range.

Redox conditions of the environment. The development of microorganisms is in close connection with the redox conditions of the environment, conventionally denoted by the symbol rH 2 . It represents the negative logarithm of the pressure of molecular hydrogen and expresses the degree of aerobicity in the environment. If the medium is saturated with molecular hydrogen, then rH 2 equals zero. At an equilibrium of oxidizing and reducing processes in the environment rH 2 equal to 28. When the environment is saturated with oxygen rH 2 equal to 41. The redox potential of the medium is affected by aeration. Various microorganisms have cardinal points of redox conditions - minimum, optimum and maximum, which determine their development.

The need of microorganisms for oxygen is very different. Anaerobes can multiply at low values rH 2 - from 8 to 10. Aerobes reproduce in the range rH 2 from 10 to 30. Intermediate forms (facultative anaerobes) can develop over a wide range rH 2 - from 0 to 30.

By regulating the redox conditions in the environment, it is possible not only to influence the growth and development of microorganisms, but also to influence the nature of the physiological and biochemical processes caused by microorganisms.

Tolerance to biological environmental factors

Types of relationships between microbes in biocenoses.

Microorganisms hard compete between themselves. This is due to the fact that microbes living in a particular biocenosis have fundamentally similar needs for energy and nutrition sources. Each microorganism adapts not only to inanimate substrates, but also to other organisms surrounding it. Such adaptation sometimes leads to the acquisition of special metabolic properties that endow the owner with the ability to occupy specific niches. For example, nitrifying bacteria can grow without organic energy sources, oxidizing ammonia or nitrite as an energy source in the absence of light; other organisms do not develop under similar conditions. Therefore, nitrifying bacteria do not experience biological competition. A significant part of bacteria participate in the competitive struggle, adapting to coexistence with other forms of life or entering into opposition with them.

Symbiosis. An example of symbiosis is the relationship between some lactic acid bacteria and yeast (lactic acid bacteria, producing lactic acid, create conditions favorable for the growth of yeast, and the waste products of yeast - vitamins stimulate the development of lactic acid bacteria), nitrogen-fixing microbes and cellulose-decomposing bacteria, cohabitation aerobes that absorb oxygen with anaerobes, etc. This kind of relationship is often observed between microorganisms and plants (for example, symbiosis of nodule bacteria with legumes, mycorrhiza - cohabitation various mushrooms with plant roots), as well as between microbes and animals.

The relationship in which the microorganism resides outside the host cells (more than large organism) are known as ectosymbiosis; when localized inside cells - as endosymbiosis.

Typical ectosymbiotic microbes - Escherichia coli, bacteria genera Bacteroides and Bifidobacterium, Proteus vulgaris, as well as other representatives of the intestinal microflora.

Relationships of a symbiotic nature have the following forms.

Metabiosis - such an existence when the waste products of some microbial species are materials for the nutrition and development of other species. For example, saprophytes break down natural proteins into peptones, amino acids and other simpler compounds. And these products serve as the starting material for nitrifying bacteria, which convert ammonia salts into nitrous and then into nitric acid.

Yeast converts sugars into ethanol, and acetic acid bacteria oxidize it to acetic acid. This form of relationship is common among soil microbes and underlies the cycle of substances in nature.

Commensalism(from Latin com + mensa - companions) - a kind of symbiosis in which only one partner benefits (without causing visible harm to the other). Commensal microorganisms colonize skin and cavities of the human body (for example, the gastrointestinal tract), without causing "visible" harm; their totality is the normal microbial flora (natural microflora). Typical ectosymbiotic commensal organisms are Escherichia coli, bifidobacteria, staphylococci, lactobacilli. Many commensal bacteria belong to the opportunistic microflora and are capable of causing diseases of the macroorganism under certain circumstances (for example, when they are introduced into the bloodstream during medical procedures).

Mutualism (from Latin mutuus - mutual) - mutually beneficial symbiotic relationship. So, microorganisms produce BABs that are necessary for the host organism (for example, B vitamins). At the same time, endo- and ectosymbionts living in macroorganisms are protected from adverse environmental conditions (desiccation and extreme temperatures) and have constant access to nutrients. Of all the types of mutualism, the most surprising is the cultivation of certain fungi by insects (beetles and termites). On the one hand, this contributes to a wider spread of fungi, on the other hand, it provides a constant source of nutrients for the larvae.

satelliteism. Some microorganisms are able to secrete metabolites that stimulate the growth of other microorganisms. For example, sarcins or staphylococci secrete growth factors that stimulate the growth of bacteria of the genus Haemophilus. Often, the joint growth of several types of microbes activates their physiological properties. Such relationships are known as satelliteism (from Latin safeties - accompanying) (Fig. 6).

Rice. 6. Synergism in microbes - around the agar block with an actinomycete culture, a zone of mold growth stimulation is visible.

Antagonism (antibiosis) - Situations when one microorganism inhibits the development of another are known as microbial antagonism (from the Greek antagonizmai - rivalry) and reflect the evolutionary forms of the struggle of microorganisms for existence (that is, for sources of nutrition and energy).

Antagonistic relationships are especially pronounced in natural habitats a large number various kinds and types of microorganisms (for example, in the soil or gastrointestinal tract) that have the same nutritional and energy requirements. In this case, the impact on a competitor can be passive or active. In the first case, microorganisms quickly utilize the substrate, depriving the opponent of " raw materials»; in the second, "they declare war until complete annihilation." The forms of extermination can be variable - from the banal absorption of smaller species to the release of highly specific products that are toxic to competitors (Fig. 7).

Rice. 7. Antagonism in microbes - around the agar block with the culture of actinomycetes, a zone of suppression of the growth of staphylococcus is visible.

The destructive effect of antagonist microorganisms is associated with their accumulation in the environment of waste products or with the release of certain biologically active substances into it - antibiotics.

As a result of such an adverse effect, the vital activity of one of the species is weakened or it dies.

Lactic acid bacteria are antagonists of putrefactive bacteria, since lactic acid inhibits the development of the latter. Ordinary soil microflora inhibits micro-organisms that are pathogenic for humans.

Antagonism is also observed between plants and microorganisms. Plants produce substances that are toxic to bacteria, fungi, and protozoa. These substances have various properties and not the same chemical nature, strength of action, etc. They were first identified by the Soviet botanist V.P. Tokin in 1928 and named phytoncides(phyton - plant, caedo - I kill).

Thus, the zone of tolerance of the microbial world is truly grandiose, its boundaries are often at the limit values ​​of environmental factors. This feature of microorganisms provides them with almost unlimited development throughout the planet.