>>Bacteria, their structure and activity

1 - mold fungus; 1 - lines; 3, 4 - scale lichens; $ - parmelia on a birch trunk; 6 - sulfur yellow tinder fungus

§ 92. Bacteria, their structure and vital activity

There is practically no place on Earth where bacteria are not found.. There are especially many bacteria in soil. 1 gram of soil can contain hundreds of millions of bacteria. The number of bacteria is different in the air of ventilated and unventilated rooms. So, in classrooms, after ventilation before the start of the lesson, bacteria are 13 times less than in the same rooms after lessons. There are few bacteria in the air high in the mountains, but the air in the streets of large cities contains many bacteria.

To get acquainted with the structural features of bacteria, consider a micropreparation of hay bacillus. Each such bacterium is only one rod-shaped cell with a thin membrane and cytoplasm. There is no typical nucleus in the cytoplasm. The nuclear substance in most bacteria is scattered in the cytoplasm. The structure of other bacteria is similar to the structure of hay bacillus.

The vast majority of bacteria are colorless. Only a few are colored purple or green. The shape of bacteria is different. There are bacteria in the form of balls; there are rod-shaped forms of bacteria - hay sticks also belong to them; there are bacteria curved and similar to spirals 185.

Some bacteria have flagella that help them move. Many bacteria join in chains, or groups, forming huge accumulations in the form of films. Some bacteria can form spores. At the same time, the content cells, shrinking, moves away from the shell, rounds off and forms on its surface, being inside the parent shell, a new, denser shell. Such a bacterial cell is called a spore. Spores persist for a very long time in the most unfavorable conditions. They withstand drying, heat and frost, do not die immediately even in boiling water. Spores are easily carried by wind, water, stick to objects. There are many of them in the air and soil. Under favorable conditions, the spore germinates and becomes a viable bacterium. Bacterial spores are adaptations for bacterial survival in adverse conditions.

Bacteria live in a variety of conditions.. Some of them live and reproduce only with access to air, others do not need it. Most types of bacteria feed on ready-made organic substances, since they do not have chlorophyll. Only a very few are able to create organic substances from inorganic ones. These are blue-green, or cyanobacteria. They played an important role in the accumulation of oxygen in the Earth's atmosphere (see p. 225).

Once in conditions favorable for development, the bacterium divides, forming two daughter cells; in some bacteria, divisions are repeated every 20 minutes and more and more new generations of bacteria appear. To destroy bacteria and their spores, they are exposed to steam at a temperature of 120 ° C for 20 minutes.

To culture hay bacillus, place some hay in a flask of water, cover the neck of the flask with cotton wool, and boil the contents for 30 minutes to kill any other bacteria that may be in the flask. The hay stick will not die when boiled.

Filter the resulting infusion of hay and put it in a room with a temperature of 20-25 degrees Celsius for several days. The hay bacillus will multiply, and soon the surface of the water will be covered with a film of bacteria.

Korchagina V.A., Biology: Plants, bacteria, fungi, lichens: Proc. for 6 cells. avg. school - 24th ed. - M.: Enlightenment, 2003. - 256 p.: ill.

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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 the colonies of many bacteria have a bright color, which is due to the release of a colored substance into the environment or pigmentation of the 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, on the ocean floor, in oil extracted from great depths, and even in hot spring water with a temperature of about 80ºС. They live on plants, fruits, in various animals and in humans in the intestines, mouth, limbs, and 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 adapted to various conditions of 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 diseases. 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, so 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 an 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 out unnecessary molecules. 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 as an energy source for such synthesis, but the energy of 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 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, a 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.

Spores are not an essential stage in the life cycle of 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

Since bacteria are distributed almost everywhere and are found in huge numbers, they largely determine the various processes that occur in nature. In autumn, the leaves of trees and shrubs fall, the above-ground grass shoots die off, old branches fall off, and 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 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 detonated 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 is a natural environment where microorganisms grow in large numbers. 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 cleanest are the waters of artesian wells and springs. Open reservoirs and rivers are very rich in bacteria. The greatest number of bacteria is found in the surface layers of 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.

In terms of species composition, the water microflora is similar to the soil microflora, but specific forms are also found. 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. The air in the countryside is 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 matter 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 of different types. The existence of each separate group of organisms depends on the chemical transformation of elements carried out by other groups.

nitrogen cycle

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

The carbon cycle

The biological transformation 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

Some fresh water reservoirs contain high concentrations of reduced iron salts. In such places, a specific bacterial microflora develops - iron bacteria, which oxidize reduced iron. They participate in the formation of marsh iron ores 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.

What are bacteria: types of bacteria, their classification

Bacteria are tiny microorganisms that have been around for thousands of years. It is impossible to see microbes with the naked eye, but we should not forget about their existence. There are a huge number of bacilli. The science of microbiology is engaged in their classification, study, varieties, features of structure and physiology.

Microorganisms are called differently, depending on their kind of actions and functions. Under a microscope, you can observe how these little creatures interact with each other. The first microorganisms were rather primitive in form, but their importance should by no means be underestimated. From the very beginning, bacilli evolved, created colonies, tried to survive in changing climatic conditions. Different vibrios are able to exchange amino acids in order to grow and develop normally as a result.

Today it is difficult to say how many species of these microorganisms are on earth (this number exceeds a million), but the most famous and their names are familiar to almost every person. It doesn’t matter what microbes are and what they are called, they all have one advantage - they live in colonies, so it is much easier for them to adapt and survive.

First, let's figure out what microorganisms exist. The simplest classification is good and bad. In other words, those that are harmful to the human body, cause many diseases and those that are beneficial. Next, we will talk in detail about what are the main beneficial bacteria and give a description of them.

You can also classify microorganisms according to their shape, characteristics. Probably, many people remember that in school textbooks there was a special table with the image of various microorganisms, and next to it was the meaning and their role in nature. There are several types of bacteria:

• cocci - small balls that resemble a chain, as they are located one behind the other;
• rod-shaped;
• spirilla, spirochetes (have a convoluted shape);
• vibrios.

Bacteria of different shapes

We have already mentioned that one of the classifications divides microbes into species depending on their shape.

Bacteria coli also have some features. For example, there are types of rod-shaped with pointed poles, with thickened, with rounded or with straight ends. As a rule, rod-shaped microbes are very different and are always in chaos, they do not line up in a chain (with the exception of streptobacilli), they do not attach to each other (except for diplobacilli).

To microorganisms of spherical forms, microbiologists include streptococci, staphylococci, diplococci, gonococci. It can be pairs or long chains of balls.

Curved bacilli are spirilla, spirochetes. They are always active but do not produce spores. Spirilla is safe for people and animals. You can distinguish spirilla from spirochetes if you pay attention to the number of curls, they are less convoluted, have special flagella on the limbs.

Types of pathogenic bacteria

For example, a group of microorganisms called cocci, and in more detail streptococci and staphylococci cause real purulent diseases (furunculosis, streptococcal tonsillitis).

Anaerobes live and develop perfectly without oxygen; for some types of these microorganisms, oxygen generally becomes deadly. Aerobic microbes need oxygen to survive.

Archaea are almost colorless unicellular organisms.

Pathogenic bacteria should be avoided because they cause infections, gram-negative microorganisms are considered resistant to antibodies. There is a lot of information about soil, putrefactive microorganisms, which are harmful, useful.

In general, spirilla are not dangerous, but some species can cause sodoku.

Varieties of beneficial bacteria

Even schoolchildren know that bacilli are useful and harmful. People know some names by ear (staphylococcus, streptococcus, plague bacillus). These are harmful creatures that interfere not only with the external environment, but also with humans. There are microscopic bacilli that cause food poisoning.

Be sure to know useful information about lactic acid, food, probiotic microorganisms. For example, probiotics, in other words good organisms, are often used for medical purposes. You ask: for what? They do not allow harmful bacteria to multiply inside a person, strengthen the protective functions of the intestine, and have a good effect on the human immune system.

Bifidobacteria are also very beneficial for the intestines. Lactic acid vibrios include about 25 species. In the human body, they are present in large quantities, but are not dangerous. On the contrary, they protect the gastrointestinal tract from putrefactive and other microbes.

Speaking of good ones, one cannot fail to mention the huge species of streptomycetes. They are known to those who took chloramphenicol, erythromycin and similar drugs.

There are microorganisms such as Azotobacter. They live in the soil for many years, have a beneficial effect on the soil, stimulate the growth of plants, cleanse the earth of heavy metals. They are irreplaceable in medicine, agriculture, medicine, food industry.

Types of bacterial variability

By their nature, microbes are very fickle, they die quickly, they can be spontaneous, induced. We will not go into details about the variability of bacteria, since this information is of more interest to those who are interested in microbiology and all its branches.

Types of bacteria for septic tanks

Residents of private homes understand the urgent need to treat wastewater, as well as cesspools. Today, drains can be quickly and efficiently cleaned with the help of special bacteria for septic tanks. For a person, this is a huge relief, since cleaning the sewer is not a pleasant thing.

We have already clarified where the biological type of wastewater treatment is used, and now let's talk about the system itself. Bacteria for septic tanks are grown in laboratories, they kill the unpleasant smell of drains, disinfect drainage wells, cesspools, and reduce the volume of wastewater. There are three types of bacteria that are used for septic tanks:

• aerobic;
• anaerobic;
• live (bioactivators).

Very often people use combined cleaning methods. Strictly follow the instructions on the preparation, make sure that the water level contributes to the normal survival of bacteria. Also, remember to use the drain at least once every two weeks so that the bacteria have something to eat, otherwise they will die. Don't forget that chlorine from cleaning powders and liquids kills bacteria.

The most popular bacteria are Dr. Robik, Septifos, Waste Treat.

Types of bacteria in urine

In theory, there should be no bacteria in the urine, but after various actions and situations, tiny microorganisms settle where they please: in the vagina, in the nose, in water, and so on. If the bacteria were found during the tests, this means that the person is suffering from diseases of the kidneys, bladder or ureters. There are several ways in which microorganisms enter the urine. Before treatment, it is very important to investigate and accurately determine the type of bacteria and the route of entry. This can be determined by biological urine culture, when the bacteria are placed in a favorable habitat. Next, the reaction of bacteria to various antibiotics is checked.

We wish you to always stay healthy. Take care of yourself, wash your hands regularly, protect your body from harmful bacteria!

Incredible Facts

The mere thought of trillions of bacteria living on our skin and in our body is terrifying to some.

"But in the same way that a person cannot live without carbon, nitrogen, protection from diseases, it also cannot live without bacteria", - says microbiologist and author of the book "Allies and Enemies: How the World Depends on Bacteria" Anna Makzulak (Anne Maczulak).

Most people learn about bacteria only in the context of certain diseases, which naturally leads to negative human attitudes towards them. “Now is the time to think about how they help us, because it is a very complex, multi-step process,” Makzulak added.

Tiny Overlords

In the soil and ocean, bacteria are the main players involved in the breakdown of organic matter and the cycling of chemical elements such as carbon and nitrogen, which are essential for human life. Due to the fact that plants and animals cannot create some of the nitrogen molecules, we must live however, soil bacteria and cyanobacteria (blue-green algae) play an absolutely indispensable role in converting atmospheric nitrogen into forms of nitrogen that plants can absorb, thereby creating amino acids and nucleic acids, which, in turn, are the building blocks of DNA. We eat plant foods and thereby reap the benefits of this whole process.

Bacteria also play a role in the circulation of another equally important component for human life. This is water. In recent years, scientists at the University of Louisiana have uncovered evidence that bacteria are a major constituent of many, if not most, of the tiny particles that cause snow and rain to form in clouds.

Bacteria and the human body

On the human body and inside it, bacteria play an equally important role. During the work of the digestive system, they help us in the digestion of food, since we are not able to do it on our own. "We get a lot more nutrients from the food we eat thanks to the bacteria," says Makzulak.

Bacteria found in the digestive system provide us with essential vitamins such as biotin and vitamin K, as well as are our main sources of nutrients. Experiments conducted on guinea pigs showed that animals raised in sterile conditions without bacteria were constantly malnourished and died young.

According to Makzulak, bacteria on the surface of the skin (about 200 species in a normal healthy person, according to researchers from New York University) actively contact each other, thereby ensuring the normal functioning of the body. It is also important to note that both external and internal bacteria, have a huge impact on the formation and development of the immune system.

According to Colorado State University microbiologist Gerald Callahan, the activity of both beneficial and harmful bacteria is exactly what subsequently determines how the immune system reacts to pathogenic changes in the body. A study published in the New England Journal of Medicine also confirmed that children who grow up in bacteria-free environments have a higher risk of developing asthma and allergies.

But still, this does not mean that beneficial bacteria cannot be dangerous. As Makzulak says, usually, beneficial and harmful bacteria are mutually exclusive. But sometimes the situation turns out quite differently. "The staphylococcus bacterium is a prime example of this because its home is all of our skin," Makzulak explains. Whole colonies of Staphylococcus aureus, living, for example, on our hand, can easily coexist with a person without harm to health, but as soon as you cut yourself or compromise your immune system in some other way, the bacteria can immediately begin to run amok, thereby causing infection.

The number of bacteria in the human body exceeds the number of human cells by 10 times. "It's a little creepy, but it will help us imagine the role these organisms play."

BACTERIA
an extensive group of unicellular microorganisms characterized by the absence of a cell nucleus surrounded by a membrane. At the same time, the genetic material of a bacterium (deoxyribonucleic acid, or DNA) occupies a very specific place in the cell - a zone called the nucleoid. Organisms with such a structure of cells are called prokaryotes ("pre-nuclear"), in contrast to all the others - eukaryotes ("true nuclear"), whose DNA is located in the nucleus surrounded by a shell. Bacteria, once considered microscopic plants, are now classified as a separate kingdom, Monera, one of five in the current classification system, along with plants, animals, fungi, and protists.

fossil evidence. Bacteria are probably the oldest known group of organisms. Layered stone structures - stromatolites - dated in some cases to the beginning of the Archaeozoic (Archaean), i.e. that arose 3.5 billion years ago - the result of the vital activity of bacteria, usually photosynthetic, the so-called. blue-green algae. Similar structures (bacterial films impregnated with carbonates) are formed now, mainly off the coast of Australia, the Bahamas, in the California and Persian Gulfs, but they are relatively rare and do not reach large sizes, because herbivorous organisms, such as gastropods, feed on them. Today, stromatolites grow mainly where these animals are absent due to the high salinity of the water or for other reasons, but before the appearance of herbivorous forms in the course of evolution, they could reach enormous sizes, constituting an essential element of oceanic shallow water, comparable to modern coral reefs. Tiny charred spheres have been found in some ancient rocks, which are also thought to be the remains of bacteria. The first nuclear, i.e. eukaryotic, cells evolved from bacteria about 1.4 billion years ago.
Ecology. There are many bacteria in the soil, at the bottom of lakes and oceans - everywhere where organic matter accumulates. They live in the cold, when the thermometer is slightly above zero, and in hot acidic springs with temperatures above 90 ° C. Some bacteria tolerate very high salinity of the environment; in particular, they are the only organisms found in the Dead Sea. In the atmosphere, they are present in water droplets, and their abundance there usually correlates with the dustiness of the air. So, in cities, rainwater contains much more bacteria than in rural areas. There are few of them in the cold air of the highlands and polar regions; nevertheless, they are found even in the lower layer of the stratosphere at an altitude of 8 km. The digestive tract of animals is densely populated with bacteria (usually harmless). Experiments have shown that they are not necessary for the life of most species, although they can synthesize some vitamins. However, in ruminants (cows, antelopes, sheep) and many termites, they are involved in the digestion of plant foods. In addition, the immune system of an animal raised in sterile conditions does not develop normally due to the lack of stimulation by bacteria. The normal bacterial "flora" of the intestine is also important for the suppression of harmful microorganisms that enter there.

STRUCTURE AND LIFE OF BACTERIA

Bacteria are much smaller than the cells of multicellular plants and animals. Their thickness is usually 0.5-2.0 microns, and their length is 1.0-8.0 microns. Some forms can barely be seen with the resolution of standard light microscopes (about 0.3 µm), but there are also known species with a length of more than 10 µm and a width that also goes beyond these limits, and a number of very thin bacteria can exceed 50 µm in length. A quarter of a million medium-sized representatives of this kingdom will fit on the surface corresponding to the point set with a pencil.
Structure. According to the peculiarities of morphology, the following groups of bacteria are distinguished: cocci (more or less spherical), bacilli (rods or cylinders with rounded ends), spirilla (rigid spirals) and spirochetes (thin and flexible hair-like forms). Some authors tend to combine the last two groups into one - spirilla. Prokaryotes differ from eukaryotes mainly in the absence of a well-formed nucleus and the presence, in a typical case, of only one chromosome - a very long circular DNA molecule attached at one point to the cell membrane. Prokaryotes also lack membrane-bound intracellular organelles called mitochondria and chloroplasts. In eukaryotes, mitochondria produce energy during respiration, and photosynthesis takes place in chloroplasts (see also CELL). In prokaryotes, the entire cell (and, first of all, the cell membrane) takes on the function of a mitochondrion, and in photosynthetic forms, at the same time, the chloroplast. Like eukaryotes, inside the bacterium are small nucleoprotein structures - ribosomes necessary for protein synthesis, but they are not associated with any membranes. With very few exceptions, bacteria are unable to synthesize sterols, essential components of eukaryotic cell membranes. Outside of the cell membrane, most bacteria are lined with a cell wall, somewhat reminiscent of the cellulose wall of plant cells, but consisting of other polymers (they include not only carbohydrates, but also amino acids and substances specific to bacteria). This shell prevents the bacterial cell from bursting when water enters it due to osmosis. On top of the cell wall is often a protective mucosal capsule. Many bacteria are equipped with flagella, with which they actively swim. Bacterial flagella are simpler and somewhat different than similar eukaryotic structures.

"TYPICAL" BACTERIAL CELL and its main structures.

Sensory functions and behavior. Many bacteria have chemical receptors that detect changes in the acidity of the environment and the concentration of various substances, such as sugars, amino acids, oxygen and carbon dioxide. Each substance has its own type of such "taste" receptors, and the loss of one of them as a result of mutation leads to partial "taste blindness". Many motile bacteria also respond to temperature fluctuations, and photosynthetic species to changes in light. Some bacteria perceive the direction of magnetic field lines, including the Earth's magnetic field, with the help of magnetite particles (magnetic iron ore - Fe3O4) present in their cells. In water, bacteria use this ability to swim along lines of force in search of a favorable environment. Conditioned reflexes in bacteria are unknown, but they have a certain kind of primitive memory. While swimming, they compare the perceived intensity of the stimulus with its previous value, i.e. determine whether it has become larger or smaller, and, based on this, maintain the direction of movement or change it.
Reproduction and genetics. Bacteria reproduce asexually: the DNA in their cell is replicated (doubled), the cell divides in two, and each daughter cell receives one copy of the parent's DNA. Bacterial DNA can also be transferred between non-dividing cells. At the same time, their fusion (as in eukaryotes) does not occur, the number of individuals does not increase, and usually only a small part of the genome (the complete set of genes) is transferred to another cell, in contrast to the "real" sexual process, in which the descendant receives a complete set of genes from each parent. Such DNA transfer can be carried out in three ways. During transformation, the bacterium absorbs "naked" DNA from the environment, which got there during the destruction of other bacteria or deliberately "slipped" by the experimenter. The process is called transformation, because in the early stages of its study, the main attention was paid to the transformation (transformation) in this way of harmless organisms into virulent ones. Fragments of DNA can also be transferred from bacteria to bacteria by special viruses - bacteriophages. This is called transduction. There is also a process that resembles fertilization and is called conjugation: bacteria are connected to each other by temporary tubular outgrowths (copulatory fimbria), through which DNA passes from the "male" cell to the "female". Sometimes bacteria contain very small extra chromosomes - plasmids, which can also be transferred from individual to individual. If at the same time plasmids contain genes that cause resistance to antibiotics, they speak of infectious resistance. It is important from a medical point of view, because it can spread between different species and even genera of bacteria, as a result of which the entire bacterial flora, say the intestines, becomes resistant to the action of certain drugs.

METABOLISM

Partly due to the small size of bacteria, the intensity of their metabolism is much higher than that of eukaryotes. Under the most favorable conditions, some bacteria can double their total mass and abundance approximately every 20 minutes. This is due to the fact that a number of their most important enzyme systems function at a very high speed. So, a rabbit needs a few minutes to synthesize a protein molecule, and bacteria - seconds. However, in the natural environment, for example, in the soil, most bacteria are "on a starvation diet", so if their cells divide, then not every 20 minutes, but every few days.
Nutrition. Bacteria are autotrophs and heterotrophs. Autotrophs ("self-feeding") do not need substances produced by other organisms. They use carbon dioxide (CO2) as the main or only source of carbon. Including CO2 and other inorganic substances, in particular ammonia (NH3), nitrates (NO-3) and various sulfur compounds, in complex chemical reactions, they synthesize all the biochemical products they need. Heterotrophs ("feeding on others") use as the main source of carbon (some species also need CO2) organic (carbon-containing) substances synthesized by other organisms, in particular sugars. Oxidized, these compounds supply energy and molecules necessary for the growth and vital activity of cells. In this sense, heterotrophic bacteria, which include the vast majority of prokaryotes, are similar to humans.
main sources of energy. If for the formation (synthesis) of cellular components mainly light energy (photons) is used, then the process is called photosynthesis, and the species capable of it are called phototrophs. Phototrophic bacteria are divided into photoheterotrophs and photoautotrophs, depending on which compounds - organic or inorganic - serve as their main source of carbon. Photoautotrophic cyanobacteria (blue-green algae), like green plants, split water molecules (H2O) using light energy. This releases free oxygen (1/2O2) and produces hydrogen (2H+), which can be said to convert carbon dioxide (CO2) into carbohydrates. In green and purple sulfur bacteria, light energy is not used to break down water, but other inorganic molecules, such as hydrogen sulfide (H2S). As a result, hydrogen is also produced, reducing carbon dioxide, but oxygen is not released. Such photosynthesis is called anoxygenic. Photoheterotrophic bacteria, such as purple nonsulfur bacteria, use light energy to produce hydrogen from organic substances, in particular isopropanol, but gaseous H2 can also serve as its source. If the main source of energy in the cell is the oxidation of chemicals, bacteria are called chemoheterotrophs or chemoautotrophs, depending on which molecules serve as the main source of carbon - organic or inorganic. In the former, organics provide both energy and carbon. Chemoautotrophs obtain energy from the oxidation of inorganic substances, such as hydrogen (to water: 2H4 + O2 to 2H2O), iron (Fe2+ to Fe3+) or sulfur (2S + 3O2 + 2H2O to 2SO42- + 4H+), and carbon from CO2. These organisms are also called chemolithotrophs, thus emphasizing that they "feed" on rocks.
Breath. Cellular respiration is the process of releasing chemical energy stored in "food" molecules for its further use in vital reactions. Respiration can be aerobic and anaerobic. In the first case, it needs oxygen. It is needed for the work of the so-called. electron transport system: electrons move from one molecule to another (energy is released) and eventually attach to oxygen along with hydrogen ions - water is formed. Anaerobic organisms do not need oxygen, and for some species of this group it is even poisonous. The electrons released during respiration are attached to other inorganic acceptors, such as nitrate, sulfate or carbonate, or (in one of the forms of such respiration - fermentation) to a certain organic molecule, in particular to glucose. See also METABOLISM.

CLASSIFICATION

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

Phylum Gracilicutes (thin-walled Gram-negative bacteria)

Class Scotobacteria (non-photosynthetic forms, e.g. myxobacteria) Class Anoxyphotobacteria (oxygen-releasing photosynthetic forms, e.g. purple sulfur bacteria) Class Oxyphotobacteria (oxygen-releasing photosynthetic forms, e.g. cyanobacteria)

Phylum Firmicutes (thick-walled Gram-positive bacteria)

Class Firmibacteria (hard-celled forms such as clostridia)
Class Thallobacteria (branched forms, e.g. actinomycetes)

Tenericutes phylum (gram-negative bacteria without cell wall)

Class Mollicutes (soft cell forms, e.g. mycoplasmas)

Type Mendosicutes (bacteria with defective cell wall)

Class Archaebacteria (ancient forms, e.g. methane formers)

Domains. Recent biochemical studies have shown that all prokaryotes are clearly divided into two categories: a small group of archaebacteria (Archaebacteria - "ancient bacteria") and all the rest, called eubacteria (Eubacteria - "true bacteria"). It is believed that archaebacteria are more primitive than eubacteria and closer to the common ancestor of prokaryotes and eukaryotes. They differ from other bacteria in several significant ways, including the composition of the ribosomal RNA (pRNA) molecules involved in protein synthesis, the chemical structure of lipids (fat-like substances), and the presence of some other substances in the cell wall instead of the protein-carbohydrate polymer murein. In the above classification system, archaebacteria are considered to be just one of the types of the same kingdom that includes all eubacteria. However, according to some biologists, the differences between archaebacteria and eubacteria are so profound that it is more correct to consider the archaebacteria in Monera as a separate sub-kingdom. Recently, an even more radical proposal has emerged. Molecular analysis has revealed such significant differences in the structure of genes between these two groups of prokaryotes that some consider their presence within the same kingdom of organisms to be illogical. In this regard, it was proposed to create a taxonomic category (taxon) of an even higher rank, calling it a domain, and to divide all living things into three domains - Eucarya (eukaryotes), Archaea (archaebacteria) and Bacteria (current eubacteria).

ECOLOGY

The two most important ecological functions of bacteria are nitrogen fixation and mineralization of organic residues.
Nitrogen fixation. The binding of molecular nitrogen (N2) to form ammonia (NH3) is called nitrogen fixation, and the oxidation of the latter to nitrite (NO-2) and nitrate (NO-3) is called nitrification. These are vital processes for the biosphere, since plants need nitrogen, but they can only assimilate its bound forms. Currently, approximately 90% (about 90 million tons) of the annual amount of such "fixed" nitrogen is provided by bacteria. The rest is produced by chemical plants or occurs during lightning discharges. Nitrogen in the air, which is approx. 80% of the atmosphere, associated mainly with the gram-negative genus Rhizobium (Rhizobium) and cyanobacteria. Rhizobium species symbiose with approximately 14,000 species of leguminous plants (family Leguminosae), which include, for example, clover, alfalfa, soybeans and peas. These bacteria live in the so-called. nodules - swellings that form on the roots in their presence. Bacteria receive organic matter (nutrition) from the plant, and in return supply the host with bound nitrogen. For a year, up to 225 kg of nitrogen per hectare is fixed in this way. Non-legume plants, such as alder, also enter into symbiosis with other nitrogen-fixing bacteria. Cyanobacteria photosynthesize like green plants, releasing oxygen. Many of them are also capable of fixing atmospheric nitrogen, which is then taken up by plants and eventually by animals. These prokaryotes serve as an important source of fixed nitrogen in the soil in general and rice fields in the East in particular, as well as its main supplier for ocean ecosystems.
Mineralization. This is the name given to the decomposition of organic residues into carbon dioxide (CO2), water (H2O) and mineral salts. From a chemical point of view, this process is equivalent to combustion, so it requires a large amount of oxygen. The upper soil layer contains from 100,000 to 1 billion bacteria per 1 g, i.e. about 2 tons per hectare. Usually, all organic residues, once in the ground, are quickly oxidized by bacteria and fungi. More resistant to decomposition is a brownish organic substance called humic acid, which is formed mainly from lignin contained in wood. It accumulates in the soil and improves its properties.

BACTERIA AND INDUSTRY

Considering the variety of chemical reactions catalyzed by bacteria, it is not surprising that they are widely used in production, in some cases since ancient times. Prokaryotes share the glory of such microscopic human helpers with fungi, primarily yeast, which provide most of the processes of alcoholic fermentation, for example, in the manufacture of wine and beer. Now that it has become possible to introduce useful genes into bacteria, causing them to synthesize valuable substances, such as insulin, the industrial use of these living laboratories has received a powerful new impetus. See also GENETIC ENGINEERING.
Food industry. Currently, bacteria are used by this industry mainly for the production of cheeses, other fermented milk products and vinegar. The main chemical reactions here are the formation of acids. Thus, when producing vinegar, bacteria of the genus Acetobacter oxidize the ethyl alcohol contained in cider or other liquids to acetic acid. Similar processes occur during sauerkraut: anaerobic bacteria ferment the sugar contained in the leaves of this plant to lactic acid, as well as acetic acid and various alcohols.
Leaching of ores. Bacteria are used to leach poor ores, i.e. transferring from them into a solution of salts of valuable metals, primarily copper (Cu) and uranium (U). An example is the processing of chalcopyrite, or copper pyrites (CuFeS2). Heaps of this ore are periodically watered with water containing chemolithotrophic bacteria of the genus Thiobacillus. In the course of their life activity, they oxidize sulfur (S), forming soluble copper and iron sulfates: CuFeS2 + 4O2 to CuSO4 + FeSO4. Such technologies greatly simplify the production of valuable metals from ores; in principle, they are equivalent to the processes occurring in nature during the weathering of rocks.
Waste recycling. Bacteria also serve to convert waste, such as sewage, into less dangerous or even useful products. Waste water is one of the acute problems of modern mankind. Their complete mineralization requires huge amounts of oxygen, and in ordinary reservoirs, where it is customary to dump these wastes, it is no longer enough to "neutralize" them. The solution lies in additional aeration of wastewater in special pools (aerotanks): as a result, mineralizing bacteria have enough oxygen to completely decompose organic matter, and drinking water becomes one of the end products of the process in the most favorable cases. The insoluble precipitate remaining along the way can be subjected to anaerobic fermentation. In order for such water treatment plants to take up as little space and money as possible, a good knowledge of bacteriology is necessary.
Other uses. Other important areas of industrial application of bacteria include, for example, flax lobe, i.e. separation of its spinning fibers from other parts of the plant, as well as the production of antibiotics, in particular streptomycin (bacteria of the genus Streptomyces).

BACTERIA CONTROL IN INDUSTRY

Bacteria are not only beneficial; the fight against their mass reproduction, for example, in food products or in the water systems of pulp and paper mills, has become a whole area of ​​activity. Food is spoiled by bacteria, fungi and their own autolysis ("self-digestion") enzymes, unless they are inactivated by heat or other means. Since bacteria are the main cause of spoilage, designing efficient food storage systems requires knowledge of the tolerance limits of these microorganisms. One of the most common technologies is milk pasteurization, which kills bacteria that cause, for example, tuberculosis and brucellosis. Milk is kept at 61-63°C for 30 minutes or at 72-73°C for only 15 seconds. This does not impair the taste of the product, but inactivates pathogenic bacteria. Wine, beer and fruit juices can also be pasteurized. The benefits of storing food in the cold have long been known. Low temperatures do not kill bacteria, but they do not allow them to grow and multiply. True, when freezing, for example, to -25 ° C, the number of bacteria decreases after a few months, but a large number of these microorganisms still survive. At temperatures just below zero, bacteria continue to multiply, but very slowly. Their viable cultures can be stored almost indefinitely after lyophilization (freezing - drying) in a medium containing protein, such as blood serum. Other well-known food preservation methods include drying (drying and smoking), adding large amounts of salt or sugar, which is physiologically equivalent to dehydration, and pickling, i.e. placed in a concentrated acid solution. With an acidity of the medium corresponding to pH 4 and below, the vital activity of bacteria is usually greatly inhibited or stopped.

BACTERIA AND DISEASE

STUDY OF BACTERIA

Many bacteria are easy to grow in the so-called. culture medium, which may include meat broth, partially digested protein, salts, dextrose, whole blood, its serum and other components. The concentration of bacteria in such conditions usually reaches about a billion per cubic centimeter, as a result of which the environment becomes cloudy. To study bacteria, it is necessary to be able to obtain their pure cultures, or clones, which are the offspring of a single cell. This is necessary, for example, to determine which type of bacteria infected the patient and to which antibiotic this type is sensitive. Microbiological samples, such as swabs taken from the throat or wounds, samples of blood, water or other materials, are highly diluted and applied to the surface of a semi-solid medium: rounded colonies develop from individual cells on it. The culture medium hardening agent is usually agar, a polysaccharide obtained from certain seaweeds and almost indigestible by any type of bacteria. Agar media are used in the form of "jambs", ie. inclined surfaces formed in test tubes standing at a large angle when the molten culture medium solidifies, or in the form of thin layers in glass Petri dishes - flat round vessels closed with a lid of the same shape, but slightly larger in diameter. Usually, in a day, the bacterial cell has time to multiply so much that it forms a colony that is easily visible to the naked eye. It can be transferred to another environment for further study. All culture media must be sterile before bacterial cultivation, and then care must be taken to prevent the settlement of undesirable microorganisms on them. To examine the bacteria grown in this way, a thin wire loop is calcined on a flame, first touching it with a colony or smear, and then with a drop of water deposited on a glass slide. Evenly distributing the taken material in this water, the glass is dried and quickly passed over the burner flame two or three times (the side with the bacteria should be turned up): as a result, the microorganisms, without being damaged, are firmly attached to the substrate. A dye is dripped onto the surface of the preparation, then the glass is washed in water and dried again. The sample can now be viewed under a microscope. Pure cultures of bacteria are identified mainly by their biochemical characteristics, i.e. determine whether they form gas or acids from certain sugars, whether they are able to digest protein (liquefy gelatin), whether they need oxygen for growth, etc. They also check whether they are stained with specific dyes. Sensitivity to certain drugs, such as antibiotics, can be determined by placing small discs of filter paper soaked with these substances on a surface inoculated with bacteria. If any chemical compound kills bacteria, a zone free from them is formed around the corresponding disk.

Collier Encyclopedia. - Open society. 2000 .