Types of bacteria and their names. The most dangerous bacteria

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, 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 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 in 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 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 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 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 from inorganic substances necessary organic compounds, 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 the 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, during the destruction of dead plant and animal residues 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.

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 long time be at rest. 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. 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 action of sunlight, during 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 mineral salts soil. 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 exploded volcanoes. atomic bombs. Neither low temperatures Antarctica, neither boiling jets of geysers, nor saturated salt solutions in salt pools, nor strong insolation of mountain peaks, nor harsh radiation nuclear reactors do not 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 in large numbers microorganisms develop. 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 in 1 ml, and contaminated - 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 are most frequently contaminated human body. On the hands are found coli, staphylococci. 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. Beginning with 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 do not connect with 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 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 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 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.

These microorganisms, or at least some of them, deserve to be treated well, as many bacteria are friendly to our organisms - in fact, they are beneficial bacteria and live in our bodies constantly, bringing only benefits. Over the past few years, scientists have discovered that of all the bacteria that live in our body, a minority is harmful to our health. In fact, most of the bacteria found in our bodies are good for us.

Thanks to the Human Microbiome Project, a list of five beneficial bacteria that live in our body has been compiled and made public. Although pathogenic strains of some of the bacteria exist, these types are rare. It should also be noted that even beneficial strains of these bacteria, if present in people with severely weakened immune system and / or get into a part of the body where they should not be - can cause disease. However, this does not happen very often. Here is a list of five beneficial bacteria that live in our bodies:

1. Bifidobacterium longum (Bifidobacterium longum)

This microorganism is found in large quantities in the intestines of infants. They produce several acids that make the gut microflora toxic to many pathogenic bacteria. Thus, the beneficial bacteria Bifidobacterium longum serve to protect people from various diseases.

Humans cannot digest many plant food molecules on their own. When present in the gastrointestinal tract, Bacteroides thetaiotamicron bacteria break down such molecules. This allows people to digest the components present in plant foods. Without these beneficial bacteria, vegetarians would be in trouble.

3. Lactobacillus Johnsonii

This bacterium is vital for humans and especially for children. It is located in the intestines and greatly facilitates the process of assimilation of milk.

4. E. coli (Escherichia Coli)

E. coli bacteria synthesize the vital vitamin K in the human gastrointestinal tract. The abundance of this vitamin allows people's blood clotting mechanism to function normally. This vitamin is also necessary for the normal functioning of the liver, kidneys and gallbladder, metabolism and normal absorption of calcium.

5. Streptococcus viridans (Viridans Streptococci)

These beneficial bacteria thrive in your throat. Although people are not born with them, over time, after a person is born, these bacteria find a way to enter the body. They multiply there so well that they leave very little room for other, more harmful bacteria to colonize, thereby protecting the human body from disease.

How to keep beneficial bacteria from dying

We need to use antibiotics only as a last resort, as antibacterial drugs in addition to pathogenic microorganisms, they also destroy beneficial microflora, as a result of which an imbalance occurs in our bodies and diseases develop. Apart from this, you can also start regularly consuming fermented foods that are rich in beneficial strains of microorganisms (beneficial bacteria), such as sauerkraut and other vegetables, dairy products(yogurt, kefir), kombucha, miso, tempeh, etc.

Washing your hands is necessary, but you should not lean heavily on washing your hands with antibacterial soap, as this also contributes to the development of a bacterial imbalance in the body.

Rice. one. Human body 90% consists of microbial cells. It contains from 500 to 1000 different types of bacteria or trillions of these amazing residents, which is up to 4 kg of total weight.

Rice. 2. Bacteria inhabiting the oral cavity: Streptococcus mutants (green). Bacteroides gingivalis, causes periodontitis (purple). Candida albicus ( yellow). Causes candidiasis of the skin and internal organs.

Rice. 7. Mycobacterium tuberculosis. Bacteria have been causing disease in humans and animals for thousands of years. Tuberculosis bacillus is extremely stable in the external environment. In 95% of cases, it is transmitted by airborne droplets. Most often affects the lungs.

Rice. 8. The causative agent of diphtheria is Corynebacterium or Leffler's bacillus. More often it develops in the epithelium of the mucous layer of the tonsils, less often in the larynx. Swelling of the larynx and enlarged lymph nodes can lead to asphyxia. The pathogen toxin is fixed on the membranes of the cells of the heart muscle, kidneys, adrenal glands and nerve ganglia and destroys them.

Rice. 9. Pathogens staph infection. Pathogenic staphylococci cause extensive lesions of the skin and its appendages, lesions of many internal organs, food poisoning, enteritis and colitis, sepsis and toxic shock.

Rice. 10. Meningococci - pathogens meningococcal infection. Up to 80% of patients are children. The infection is transmitted by airborne droplets from sick and healthy carriers of the bacteria.

Rice. 11. Whooping cough bordetella.

Rice. 12. The causative agents of scarlet fever are streptococci pyogenes.

Harmful bacteria of water microflora

Rice. 13. Shigella. The pathogens cause bacillary dysentery. Shigella destroy the epithelium of the colon mucosa, causing severe ulcerative colitis. Their toxins affect the myocardium, nervous and vascular systems.

Rice. fourteen. . Vibrios do not destroy the cells of the mucous layer of the small intestine, but are located on their surface. The toxin cholerogen is released, the action of which leads to a violation of water-salt metabolism, in connection with which the body loses up to 30 liters of fluid per day.

Rice. 15. Salmonella - causative agents of typhoid and paratyphoid. Affect the epithelium and lymphoid elements small intestine. With the blood flow they enter Bone marrow, spleen and gallbladder from which pathogens enter the small intestine again. As a result of immune inflammation, the wall of the small intestine ruptures and peritonitis occurs.

Rice. 16. Causative agents of tularemia (coccobacteria blue color). Affects the respiratory and intestines. They have the peculiarity of penetrating into the human body through integral skin and mucous membranes of the eyes, nasopharynx, larynx and intestines. A feature of the disease is the defeat of the lymph nodes (primary bubo).

Rice. 17. Leptospira. Affect the human capillary network, often the liver, kidneys and muscles. The disease is called infectious jaundice.

Harmful bacteria of soil microflora

Rice. 18. The causative agent of anthrax. For decades, it remains in the soil in a spore-like state. A particularly dangerous disease. Its second name is malignant carbuncle. The prognosis of the disease is unfavorable.

Rice. 19. The causative agent of botulism releases the strongest toxin. 1 mcg of this poison kills a person. Botulinum toxin strikes nervous system, oculomotor nerves up to paralysis and cranial nerves. Mortality from botulism reaches 60%.

Rice. 20. The causative agents of gas gangrene multiply very quickly in soft tissues body without access to air, causing severe damage. In a spore-like state, it remains in the external environment for a long time.

Rice. 21. Putrefactive bacteria.

Rice. 22. Defeat by putrefactive bacteria of food.

Harmful bacteria infecting wood

Rice. 23. The photo shows how the house fungus destroyed the wooden floor beams.

Rice. 24. Spoiled appearance logs (blue) affected by a wood-staining fungus.

Rice. 25. House mushroom Merulius Lacrimans. a - cotton-like mycelium; b - young fruiting body; c - old fruiting body; d - old mycelium, cords and rotten wood.

Harmful bacteria in food

Rice. 26. Bread affected by mold.

Rice. 27. Cheese affected by mold and putrefactive bacteria.

Rice. 28. "Wild yeast" Pichia pastoris. Photo taken at 600x magnification. A vicious pest of beer. Found ubiquitously in nature.

Harmful bacteria that break down dietary fats

Rice. 29. Caviar oil affected by fat-splitting bacteria.

Harmful bacteria affecting eggs and egg products

Rice. 30. Spoiled eggs.

Harmful bacteria in canned food

Rice. 31. Canned meat affected by acetic acid bacteria, as a result of which the contents of the canned food become sour.

Rice. 32. Bloated canned food may contain botulinum rods and perfringens rods. It inflates the jar with carbon dioxide, which is released by bacteria during reproduction.

Harmful bacteria in grain products and bread

Rice. 33. In the photo, the ergot is purple. Low doses of ergot cause severe pain, mental disorders and aggressive behavior. High doses of ergot cause painful death. Its action is associated with muscle contraction under the influence of alkaloids of the fungus.

Rice. 34. Mushroom fungus.

Rice. 35. Spores of green, white and capitate mold can get from the air on already baked bread and infect it.

Harmful bacteria that affects fruits, vegetables and berries

Rice. 36. Defeat of berries by mold fungi.

Rice. 37. Skin lesions in yersiniosis.

harmful bacteria penetrate into the human body with food, through the air, wounds and mucous membranes. The severity of diseases caused by pathogenic microbes depends on the poisons they produce and the toxins that occur during their mass death. Over the millennia, they have acquired many devices that allow them to penetrate and stay in the tissues of a living organism and resist immunity.

To study the harmful effects of microorganisms on the body and develop preventive actions- that's the task of man!

Structure

Bacteria are very small living organisms. They can only be seen under a very high magnification microscope. All bacteria are unicellular. Internal structure bacterial cells are not like plant and animal cells. They do not have a nucleus or plastids. The nuclear substance and pigments are present, but in a "dispersed" state. The form is varied.

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. Often, an additional protective layer of mucus is produced on top of the cell wall in bacteria - a capsule. 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.

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.

Spore formation

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. Spores in bacteria serve to endure adverse conditions. They are formed from the inside of the contents of the cell. In this case, a new, denser shell is formed around the spore. Spores can tolerate very low temperatures (down to -273 ° C) and very high ones. Spores are not killed by boiling water.

Food

Many bacteria have chlorophyll and other pigments. They carry out photosynthesis, like plants (cyanobacteria, purple bacteria). Other bacteria obtain energy from inorganic substances - sulfur, iron compounds and others, but the source of carbon, as in photosynthesis, is carbon dioxide.

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 role of bacteria in nature. Distribution and ecology

Bacteria are ubiquitous: in water bodies, air, soil. There are the least of them in the air (but not in crowded places). In the waters of rivers there can be up to 400,000 of them in 1 cm 3, and in the soil - up to 1,000,000,000 in 1 g. Bacteria have different attitudes towards oxygen: for some it is necessary, for others it is destructive. For most bacteria, temperatures between +4 and +40 °C are most favorable. Direct sunlight kills many bacteria.

Occurring in huge numbers (the number of their species reaches 2500), bacteria play an exceptionally important role in many natural processes. Together with fungi and soil invertebrates, they participate in the decomposition of plant residues (falling leaves, branches, etc.) to humus. The activity of saprophytic bacteria leads to the formation of mineral salts, which are absorbed by the roots of plants. Nodule bacteria living in the tissues of the moth roots, as well as some free-living bacteria, have a remarkable ability to assimilate atmospheric nitrogen, which is inaccessible to plants. Thus, bacteria participate in the cycle of substances in nature.

Soil microflora. The number of bacteria in the soil is extremely high - 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 water bodies. 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.

The importance of bacteria in human life

Fermentation processes are of great importance; this is what is generally called the decomposition of carbohydrates. So, as a result of fermentation, milk turns into kefir and other products; ensiling fodder is also fermentation. Fermentation also occurs in the human intestine. Without the appropriate bacteria (such as E. coli), the intestines cannot function normally. Rotting, useful in nature, is highly undesirable in everyday life (for example, damage meat products). Fermentation (for example, souring milk) is not always useful either. So that the products do not deteriorate, they are salted, dried, canned, kept in refrigerators. Thus, the activity of bacteria is reduced.

Pathogenic bacteria

Science and life // Illustrations

Staphylococcus aureus.

Spirilla.

Trypanosoma.

Rotaviruses.

Rickettsia.

Yersinia.

Leishmania.

Salmonella.

Legionella.

Even 3,000 years ago, the great Greek Hippocrates guessed that contagious diseases are caused and carried by living beings. He called them miasma. But the human eye could not distinguish them. At the end of the 17th century, the Dutchman A. Leeuwenhoek created a fairly powerful microscope, and only then was it possible to describe and draw a variety of forms of bacteria - single-celled organisms, many of which are pathogens of various infectious diseases person. Bacteria is one of the types of microbes (“microbe” - from the Greek “micros” - small and “bios” - life), however, the most numerous.

After the discovery of microbes and the study of their role in human life, it turned out that the world of these smallest organisms is very diverse and requires a certain systematization and classification. And today, experts use a system according to which the first word in the name of a microorganism means the genus, and the second - the species name of the microbe. These names (usually Latin or Greek) are "speaking". Thus, the name of some microorganisms reflects some of the most striking features of their structure, in particular, the form. This group primarily includes bacteria. In form, all bacteria are divided into spherical - cocci, rod-shaped - actually bacteria and convoluted - spirilla and vibrios.

globular bacteria- pathogenic cocci (from the Greek "coccus" - grain, berry), microorganisms that differ from each other in the location of cells after their division.

The most common of them are:

- staphylococci(from the Greek "stafile" - a bunch of grapes and "kokkus" - grain, berry), which received this name because characteristic form- clusters resembling bunches of grapes. The type of these bacteria has the most pathogenic effect. staphylococcus aureus(“Staphylococcus aureus”, as it forms clusters of golden color), causing various purulent diseases and food intoxications;

- streptococci(from the Greek "streptos" - a chain), whose cells after division do not diverge, but form a chain. These bacteria are the causative agents of various inflammatory diseases(tonsillitis, bronchopneumonia, otitis media, endocarditis and others).

rod-shaped bacteria, or rods,- these are microorganisms of a cylindrical shape (from the Greek "bacterion" - a stick). From their name came the name of all such microorganisms. But those bacteria that form spores (a protective layer that protects against adverse effects environment), are called bacilli(from the Latin "bacillum" - a stick). The spore-forming rods include the anthrax bacillus, a terrible disease known since ancient times.

The twisted shapes of bacteria are spirals. For example, spirilla(from Latin "spira" - bend) are bacteria that have the form of spirally curved rods with two or three curls. These are harmless microbes, with the exception of the causative agent of "rat bite disease" (Sudoku) in humans.

A peculiar form is also reflected in the name of microorganisms belonging to the family spirochete(from Latin "spira" - bend and "hate" - mane). For example, members of the family leptospira are distinguished by an unusual shape in the form of a thin thread with small, closely spaced curls, which makes them look like a thin twisted spiral. And the very name "leptospira" is translated as such - "narrow spiral" or "narrow curl" (from the Greek "leptos" - narrow and "spera" - gyrus, curl).

corynebacteria(causative agents of diphtheria and listeriosis) have characteristic club-shaped thickenings at the ends, as indicated by the name of these microorganisms: from lat. "korine" - a mace.

Today all known viruses also grouped into genera and families, including on the basis of their structure. Viruses are so small that in order to see them through a microscope, it must be much stronger than a conventional optical one. An electron microscope magnifies hundreds of thousands of times. Rotaviruses got its name from the Latin word "rota" - a wheel, since virus particles under an electron microscope look like small wheels with a thick sleeve, short spokes and a thin rim.

And the name of the family coronaviruses due to the presence of villi, which are attached to the virion through a narrow stem and expand towards the distant end, resembling the solar corona during an eclipse.

The name of some microorganisms is associated with the name of the organ they infect or the disease they cause. For example, title "meningococci" It is formed from two Greek words: “meningos” - the meninges, since these microbes mainly affect it, and “coccus” - a grain, indicating that they belong to spherical bacteria - cocci. The name is derived from the Greek word "pneumon" (lung). "pneumococci" These bacteria cause lung disease. Rhinoviruses- causative agents of a contagious rhinitis, hence the name (from the Greek "rhinos" - nose).

The origin of the name of a number of microorganisms is also due to their other most characteristic features. So, a distinctive feature of vibrios - bacteria in the form of a short curved rod - the ability to rapid oscillatory movements. Their name is derived from the French word vibrator- vibrate, vibrate, vibrate. Among the vibrios, the causative agent of cholera, which is called "cholera vibrio", is the most famous.

Bacteria of the genus proteus(Proteus) refer to the so-called microbes that are dangerous for some, but not for others. In this regard, they were named after the sea deity from ancient Greek mythology - Proteus, who was credited with the ability to arbitrarily change his appearance.

Monuments are erected to great scientists. But sometimes the names of microorganisms discovered by them also become monuments. For example, microorganisms that occupy an intermediate position between viruses and bacteria have been named "rickettsia" in honor of the American explorer Howard Taylor Ricketts (1871-1910), who died from typhus in the study of the causative agent of this disease.

The causative agents of dysentery were thoroughly studied by the Japanese scientist K. Shiga in 1898, in his honor they subsequently received their generic name - "shigella".

Brucella(causative agents of brucellosis) are named after the English military doctor D. Bruce, who in 1886 for the first time managed to isolate these bacteria.

Bacteria grouped in a genus "yersinia", named after the famous Swiss scientist A. Yersin, who discovered, in particular, the causative agent of the plague - Yersinia pestis.

By the name of the English doctor V. Leishman, the simplest unicellular organisms (causative agents of leishmaniasis) are named leishmania, described in detail in 1903.

The generic name is associated with the name of the American pathologist D. Salmon "salmonella", rod-shaped intestinal bacteria that causes diseases such as salmonellosis and typhoid fever.

And the German scientist T. Escherich owe their name Escherichia- Escherichia coli, first isolated and described by him in 1886.

In the origin of the name of some microorganisms, a certain role was played by the circumstances under which they were discovered. For example, generic name "legionella" appeared after an outbreak in 1976 in Philadelphia among the delegates of the convention of the American Legion (an organization that unites US citizens - participants in international wars) respiratory disease caused by these bacteria - they were transmitted through the air conditioner. BUT coxsackie viruses were first isolated from children with polio in 1948 in the village of Coxsackie (USA), hence the name.