different bacteria. Kingdom of bacteria - general characteristics

Bacteria are microorganisms that consist of only one cell. A characteristic feature of bacteria is the absence of a clearly defined nucleus. That is why they are called "prokaryotes", which means - nuclear-free.

About ten thousand species of bacteria are now known to science, but there is an assumption that there are more than a million species of bacteria on earth. Bacteria are believed to be the oldest organisms on earth. They live almost everywhere - in water, soil, atmosphere and inside other organisms.

Appearance

Bacteria are very small and can only be seen with a microscope. The form of bacteria is quite diverse. The most common forms are in the form of sticks, balls and spirals.

Rod-shaped bacteria are called "bacilli".

Bacteria in the form of balls are cocci.

Bacteria in the form of spirals are spirilla.

The shape of a bacterium determines its mobility and ability to attach to a particular surface.

The structure of bacteria

Bacteria have a fairly simple structure. These organisms have several basic structures - the nucleoid, cytoplasm, membrane and cell wall, in addition, many bacteria have flagella on the surface.

Nucleoid- This is a kind of nucleus, it contains the genetic material of the bacterium. It consists of only one chromosome, which looks like a ring.

Cytoplasm surrounds the nucleoid. The cytoplasm contains important structures - ribosomes, necessary for bacteria to synthesize protein.

Membrane, covering the cytoplasm from the outside, plays an important role in the life of the bacterium. It delimits the internal contents of the bacterium from the external environment and ensures the processes of cell exchange with the environment.

Outside, the membrane is surrounded cell wall.

The number of flagella can be different. Depending on the species, one bacterium has from one to a thousand flagella, but there are bacteria without them. Bacteria need flagella to move in space.

Bacteria nutrition

Bacteria have two types of nutrition. Some of the bacteria are autotrophs and the other are heterotrophs.

Autotrophs themselves create nutrients through chemical reactions, while heterotrophs feed on organic substances that other organisms have created.

Reproduction of bacteria

Bacteria reproduce by division. Before the division process, the chromosome located inside the bacterium doubles. Then the cell is divided in two. The result is two identical daughter cells, each of which receives a copy of the mother's chromosome.

Importance of bacteria

Bacteria play an important role in the cycle of substances in nature - they turn organic residues into inorganic substances. If there were no bacteria, then the whole earth would be covered with fallen trees, fallen leaves and dead animals.

Bacteria play a dual role in human life. Some bacteria are of great benefit, while others cause significant harm.

Many bacteria are pathogenic and cause various diseases, such as diphtheria, typhoid, plague, tuberculosis, cholera, and others.

However, there are bacteria that benefit people. So in the human digestive system live bacteria that contribute to normal digestion. And lactic acid bacteria have long been used by people for the production of lactic acid products - cheeses, yogurt, kefir, etc. Bacteria also play an important role in the fermentation of vegetables and the production of vinegar.

Bacteria summary.

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 are used by plants. Bacteria obtain carbohydrates and mineral salts from plants. Thus, there is a close relationship between the leguminous plant and root nodule bacteria, which is useful for both one and the other organism. This phenomenon is called symbiosis.

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

Distribution in nature

Microorganisms are ubiquitous. The only exceptions are the craters of active volcanoes and small areas in the epicenters of 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, location, 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.

The kingdom "Bacteria" consists of bacteria and blue-green algae, the common characteristic of which is their small size and the absence of a nucleus separated by a membrane from the cytoplasm.

Who are bacteria

Translated from the Greek "bakterion" - a stick. For the most part, microbes are single-celled organisms invisible to the naked eye that multiply by fission.

Who opened them

For the first time, a researcher from Holland, who lived in the 17th century, Anthony Van Leeuwenhoek, was able to see the smallest unicellular organisms in a homemade microscope. He began to study the world around him through a magnifying glass while working in a haberdashery store.

Anthony Van Leeuwenhoek (1632 - 1723)

Subsequently, Leeuwenhoek focused on the manufacture of lenses capable of magnification up to 300 times. In them, he considered the smallest microorganisms, describing the information received and transferring what he saw to paper.

In 1676, Leeuwenhoek discovered and presented information about microscopic creatures, which he gave the name "animalcules".

What do they eat

The smallest microorganisms existed on Earth long before the appearance of man. They are ubiquitous, feeding on organic food and inorganic substances.

Bacteria are divided into autotrophic and heterotrophic according to the way they assimilate nutrients. For the existence and development of heterotrophs, they use waste products, organic decomposition of living organisms.

Representatives of bacteria

Biologists have identified about 2,500 groups of various bacteria.

According to their form, they are divided into:

cocci having spherical outlines;
bacilli - in the form of a stick;
vibrios having bends;
spirilla - spiral shape;
streptococci, consisting of chains;
staphylococci, forming clusters resembling grapes.

According to the degree of influence on the human body, prokaryotes can be divided into:

useful;
harmful.

Microbes dangerous to humans include staphylococci and streptococci, which cause purulent diseases.

Bifido bacteria, acidophilus, which stimulate the immune system and protect the gastrointestinal tract, are considered useful.

How real bacteria reproduce

Reproduction of all types of prokaryotes occurs mainly by division, followed by growth to the original size. Reaching a certain size, an adult microorganism splits into two parts.

Less commonly, reproduction of similar unicellular organisms is performed by budding and conjugation. When budding on the parent microorganism, up to four new cells grow, followed by the death of the adult part.

Conjugation is considered the simplest sexual process in unicellular organisms. Most often, bacteria that live in animal organisms multiply in this way.

Bacteria symbionts

Microorganisms involved in digestion in the human intestine are a prime example of symbiont bacteria. Symbiosis was first discovered by the Dutch microbiologist Martin Willem Beijerinck. In 1888, he proved the mutually beneficial close cohabitation of unicellular and legume plants.

Living in the root system, symbionts, eating carbohydrates, supply the plant with atmospheric nitrogen. Thus, legumes increase fertility without impoverishing the soil.

Many successful symbiotic examples are known involving bacteria and:

person;
algae;
arthropods;
sea animals.

Microscopic single-celled organisms assist the systems of the human body, contribute to the purification of wastewater, participate in the cycle of elements and work to achieve common goals.

Why bacteria are isolated in a special kingdom

These organisms are characterized by the smallest size, the absence of a formed nucleus and an exceptional structure. Therefore, despite the external similarity, they cannot be attributed to eukaryotes with a well-formed cell nucleus, limited from the cytoplasm by a membrane.

Thanks to all the features in the 20th century, scientists identified them as a separate kingdom.

The most ancient bacteria

The smallest single-celled organisms are considered the first life to have arisen on Earth. Researchers in 2016 discovered buried cyanobacteria in Greenland that are about 3.7 billion years old.

In Canada, traces of microorganisms that lived about 4 billion years ago in the ocean were found.

Functions of bacteria

In biology, between living organisms and the habitat, bacteria perform the following functions:

processing of organic substances into minerals;
nitrogen fixation.

In human life, unicellular microorganisms play an important role from the first minutes of birth. They provide a balanced intestinal microflora, affect the immune system, maintain the water-salt balance.

storage material of bacteria

Spare nutrients in prokaryotes accumulate in the cytoplasm. Their accumulation occurs in favorable conditions, and is consumed during the period of starvation.

The reserve substances of bacteria include:

polysaccharides;
lipids;
polypeptides;
polyphosphates;
sulfur deposits.

The main feature of bacteria

The function of the nucleus in prokaryotes is performed by the nucleoid.

Therefore, the main feature of bacteria is the concentration of hereditary material in one chromosome.

Why are representatives of the kingdom of bacteria classified as prokaryotes?

The absence of a formed nucleus was the reason for classifying bacteria as prokaryotic organisms.

How bacteria tolerate adverse conditions

Microscopic prokaryotes are able to endure adverse conditions for a long time, turning into spores. There is a loss of water by the cell, a significant decrease in volume and a change in shape.

Spores become insensitive to mechanical, temperature and chemical influences. Thus, the property of viability is preserved and effective resettlement is carried out.

Conclusion

Bacteria are the oldest form of life on Earth, known long before the appearance of man. They are present everywhere: in the surrounding air, water, in the surface layer of the earth's crust. Plants, animals and humans serve as habitats.

Active study of unicellular organisms began in the 19th century and continues to this day. These organisms are a major part of people's daily lives and have a direct impact on human existence.

The body of a bacterium is represented by a single cell. The forms of bacteria are varied. The structure of bacteria differs from the structure of animal and plant cells.

The cell lacks a nucleus, mitochondria and plastids. The carrier of hereditary information DNA is located in the center of the cell in a folded form. Microorganisms that do not have a true nucleus are classified as prokaryotes. All bacteria are prokaryotes.

It is assumed that on earth there are over a million species of these amazing organisms. To date, about 10 thousand species have been described.

A bacterial cell has a wall, cytoplasmic membrane, cytoplasm with inclusions, and a nucleotide. Of the additional structures, some cells have flagella, pili (a mechanism for sticking together and holding on to the surface), and a capsule. Under adverse conditions, some bacterial cells are able to form spores. The average size of bacteria is 0.5-5 microns.

The external structure of bacteria

Rice. 1. The structure of a bacterial cell.

cell wall

The cell wall of a bacterial cell is its protection and support. It gives the microorganism its specific shape.
The cell wall is permeable. Nutrients pass through it inside and metabolic products (metabolism) out.
Some types of bacteria produce a special mucus that resembles a capsule that protects them from drying out.
Some cells have flagella (one or more) or villi that help them move.
In bacterial cells that turn pink on Gram stain ( gram negative), the cell wall is thinner, multilayered. Enzymes that break down nutrients are released to the outside.
Bacteria that turn purple on Gram stain gram-positive), the cell wall is thick. Nutrients that enter the cell are broken down in the periplasmic space (the space between the cell wall and the cytoplasmic membrane) by hydrolytic enzymes.
There are numerous receptors on the surface of the cell wall. Cell killers are attached to them - phages, colicins and chemical compounds.
Wall lipoproteins in some types of bacteria are antigens, which are called toxins.
With prolonged treatment with antibiotics and for a number of other reasons, some cells lose their membrane, but retain the ability to reproduce. They acquire a rounded shape - an L-shape and can be stored for a long time in the human body (cocci or tuberculosis bacilli). Unstable L-forms have the ability to return to their original form (reversion).

Rice. 2. In the photo, the structure of the bacterial wall of gram-negative bacteria (left) and gram-positive (right).

Capsule

Under adverse environmental conditions, the bacteria form a capsule. The microcapsule adheres tightly to the wall. It can only be seen with an electron microscope. The macrocapsule is often formed by pathogenic microbes (pneumococci). In Klebsiella pneumonia, a macrocapsule is always found.

Rice. 3. In the photo, pneumococcus. The arrows indicate the capsule (electron diffraction pattern of an ultrathin section).

capsule-like shell

The capsule-like shell is a formation loosely associated with the cell wall. Thanks to bacterial enzymes, the capsule-like shell is covered with carbohydrates (exopolysaccharides) of the external environment, which ensures adhesion of bacteria to different surfaces, even completely smooth ones.

For example, streptococci, entering the human body, are able to stick together with teeth and heart valves.

The functions of the capsule are diverse:

protection from aggressive environmental conditions,
ensuring adhesion (adhesion) with human cells,
possessing antigenic properties, the capsule has a toxic effect when introduced into a living organism.

Rice. 4. Streptococci are able to stick together with tooth enamel and, together with other microbes, are the cause of caries.

Rice. 5. In the photo, the defeat of the mitral valve in rheumatism. The reason is streptococci.

Flagella

Some bacterial cells have flagella (one or more) or villi that help them move. The flagella contain the contractile protein flagelin.
The number of flagella can be different - one, a bunch of flagella, flagella at different ends of the cell or over the entire surface.
Movement (random or rotational) is carried out as a result of the rotational movement of the flagella.
The antigenic properties of flagella have a toxic effect in the disease.
Bacteria that do not have flagella, being covered with mucus, are able to glide. Aquatic bacteria contain vacuoles in the amount of 40-60, filled with nitrogen.

They provide diving and ascent. In the soil, the bacterial cell moves through the soil channels.

Rice. 6. Scheme of attachment and operation of the flagellum.

Rice. 7. The photo shows different types of flagellated microbes.

Rice. 8. The photo shows different types of flagellated microbes.

drinking

Pili (villi, fimbriae) cover the surface of bacterial cells. The villus is a helically twisted thin hollow thread of protein nature.
General drank provide adhesion (adhesion) with host cells. Their number is huge and ranges from several hundred to several thousand. From the moment of attachment, any .
sex saws promote the transfer of genetic material from the donor to the recipient. Their number is from 1 to 4 per cell.

Rice. 9. The photo shows E. coli. Visible flagella and drinking. The photo was taken using a tunneling microscope (STM).

Rice. 10. The photo shows numerous pili (fimbriae) in cocci.

Rice. 11. The photo shows a bacterial cell with fimbriae.

cytoplasmic membrane

The cytoplasmic membrane is located under the cell wall and is a lipoprotein (up to 30% lipids and up to 70% proteins).
Different bacterial cells have different lipid composition of membranes.
Membrane proteins perform many functions. Functional proteins are enzymes due to which the synthesis of its various components occurs on the cytoplasmic membrane, etc.
The cytoplasmic membrane consists of 3 layers. The double phospholipid layer is permeated with globulins, which ensure the transport of substances into the bacterial cell. If it fails, the cell dies.
The cytoplasmic membrane is involved in sporulation.

Rice. 12. The photo clearly shows a thin cell wall (CS), a cytoplasmic membrane (CPM) and a nucleotide in the center (bacterium Neisseria catarrhalis).

The internal structure of bacteria

Rice. 13. The photo shows the structure of a bacterial cell. The structure of a bacterial cell differs from the structure of animal and plant cells - the cell lacks a nucleus, mitochondria and plastids.

Cytoplasm

The cytoplasm is 75% water, the remaining 25% is mineral compounds, proteins, RNA and DNA. The cytoplasm is always dense and motionless. It contains enzymes, some pigments, sugars, amino acids, a supply of nutrients, ribosomes, mesosomes, granules and all sorts of other inclusions. In the center of the cell, a substance is concentrated that carries hereditary information - the nucleoid.

Granules

The granules are made up of compounds that are a source of energy and carbon.

mesosomes

Mesosomes are cell derivatives. They have a different shape - concentric membranes, vesicles, tubules, loops, etc. Mesosomes have a connection with the nucleoid. Participation in cell division and spore formation is their main purpose.

Nucleoid

The nucleoid is analogous to the nucleus. It is located in the center of the cell. DNA is localized in it - the carrier of hereditary information in a folded form. The untwisted DNA reaches a length of 1 mm. The nuclear substance of a bacterial cell does not have a membrane, a nucleolus and a set of chromosomes, and is not divided by mitosis. Before division, the nucleotide is doubled. During division, the number of nucleotides increases to 4.

Rice. 14. The photo shows a section of a bacterial cell. A nucleotide is visible in the central part.

Plasmids

Plasmids are autonomous molecules coiled into a ring of double-stranded DNA. Their mass is much less than the mass of a nucleotide. Despite the fact that hereditary information is encoded in the DNA of plasmids, they are not vital and necessary for a bacterial cell.

Rice. 15. The photo shows a bacterial plasmid. The photo was taken with an electron microscope.

Ribosomes

Ribosomes of a bacterial cell are involved in protein synthesis from amino acids. Ribosomes of bacterial cells are not united in the endoplasmic reticulum, as in cells that have a nucleus. It is ribosomes that often become the "target" for many antibacterial drugs.

Inclusions

Inclusions are metabolic products of nuclear and non-nuclear cells. They represent a supply of nutrients: glycogen, starch, sulfur, polyphosphate (valutin), etc. When stained, inclusions often take on a different appearance than the color of the dye. You can diagnose by currency.

Shapes of bacteria

The shape of a bacterial cell and its size are of great importance in their identification (recognition). The most common forms are spherical, rod-shaped and convoluted.

Table 1. Main forms of bacteria.

globular bacteria

Spherical bacteria are called cocci (from the Greek coccus - grain). They are arranged one at a time, two at a time (diplococci), in bags, chains and like bunches of grapes. This arrangement depends on the mode of cell division. The most harmful microbes are staphylococci and streptococci.

Rice. 16. The photo shows micrococci. Bacteria are round, smooth, white, yellow and red. Micrococci are ubiquitous in nature. They live in different cavities of the human body.

Rice. 17. In the photo, diplococcus bacteria - Streptococcus pneumoniae.

Rice. 18. Sarcina bacteria in the photo. Coccoid bacteria are combined into packets.

Rice. 19. In the photo, streptococcus bacteria (from the Greek "streptos" - a chain).

Arranged in chains. They are the causative agents of a number of diseases.

Rice. 20. In the photo, the bacteria are "golden" staphylococci. Arranged like "bunch of grapes". The clusters have a golden color. They are the causative agents of a number of diseases.

rod-shaped bacteria

Rod-shaped bacteria that form spores are called bacilli. They are cylindrical in shape. The most prominent representative of this group is the bacillus. Bacilli include plague and hemophilic rods. The ends of rod-shaped bacteria can be pointed, rounded, truncated, expanded, or split. The shape of the sticks themselves can be correct and incorrect. They can be arranged one at a time, two at a time, or form chains. Some bacilli are called coccobacilli because they are round in shape. But, nevertheless, their length exceeds the width.

Diplobacilli are double rods. Anthrax sticks form long threads (chains).

The formation of spores changes the shape of the bacilli. In the center of the bacilli, spores form in butyric bacteria, giving them the appearance of a spindle. In tetanus sticks - at the ends of the bacilli, giving them the appearance of drumsticks.

Rice. 21. The photo shows a rod-shaped bacterial cell. Multiple flagella are visible. The photo was taken with an electron microscope. Negative.

Rice. 22. In the photo, rod-shaped bacteria forming chains (anthrax rods).

In our world there is a huge number of bacteria. Some of them are good and some are bad. Some we know better, others worse. In our article, we have compiled a list of the most famous bacteria living among us and in our body. The article is written with a share of humor, so do not judge strictly.

Provides "face - control" in your insides

Lactobacilli (Lactobacillus plantarum) living in the human digestive tract since prehistoric times, do a great and important job. Like vampire garlic, they scare away pathogenic bacteria, preventing them from settling in your stomach and upsetting your intestines. welcome! Pickles and tomatoes and sauerkraut will bolster the strength of bouncers, but know that hard training and stress from exercise will shorten their ranks. Add some blackcurrant to your protein shake. These berries reduce fitness stress due to their antioxidant content.

2. PROTECTOR OF THE BELLY Helicobacter pylori

Stop hunger pangs at 3 p.m.

Another bacteria living in the digestive tract, Helicobacter pylori, develops from your childhood and helps you maintain a healthy weight throughout your life by controlling the hormones responsible for feeling hungry! Eat 1 apple every day.

These fruits produce lactic acid in the stomach, in which most harmful bacteria cannot survive, but which Helicobacter pylori adores. However, keep H. pylori within limits, they can work against you and cause stomach ulcers. Make scrambled eggs with spinach for breakfast: the nitrates from these green leaves thicken the walls of the stomach, protecting it from excess lactic acid.

3. Pseudomonas aeruginosa head

Likes showers, hot tubs and pools

The warm-water bacterium Pseudomonas aeruginosa crawls under the scalp through the pores of the hair follicles, causing an infection accompanied by itching and pain in the affected areas.

Don't want to put on a bathing cap every time you take a bath? Fend off a comber intrusion with a chicken or salmon and egg sandwich. A large amount of protein is necessary for the follicles to be healthy and effectively fight foreign bodies. Don't forget about fatty acids, which are absolutely essential for a healthy scalp. This will help you 4 cans of canned tuna or 4 medium avocados per week. No more.

4. Harmful bacteria Corynebacterium minutissimum

High tech protozoan

Harmful bacteria can lurk in the most unexpected places. For example, Corynebacterium minutissimum, which causes a rash, loves to live on the touchscreens of phones and tablet computers. Destroy them!

Strangely, no one has yet developed a free application that fights these germs. But many companies produce cases for phones and tablets with an antibacterial coating, which is guaranteed to stop the growth of bacteria. And try not to rub your hands together when you dry them after washing - it can reduce the bacteria population by 37%.

5. NOBLE CRAUNT Escherichia coli

Good bad bacteria

The bacterium Escherichia coli is believed to cause tens of thousands of infectious diseases every year. But it only gives us problems when it finds a way to leave the colon and mutate into a disease-causing strain. Normally, it is quite useful for life and provides the body with vitamin K, which maintains the health of the arteries, preventing heart attacks.

To keep this headline bacterium in check, include legumes in your diet five times a week. The fiber in the beans is not broken down, but moves to the large intestine, where E. coli can feast on it and continue their normal reproductive cycle. Black beans are the richest in fiber, then Ithlim, or moon-shaped, and only then is the usual red bean that we are used to. Legumes not only keep bacteria in check, but also limit your afternoon appetite with their fiber, and increase the efficiency of the absorption of nutrients by the body.

6. BURNING Staphylococcusaureus

Eats the youth of your skin

Most often, boils and pimples are caused by the bacterium Staphylococcusaureus, which lives on the skin of most people. Acne is, of course, unpleasant, but, having penetrated through damaged skin into the body, this bacterium can cause more serious diseases: pneumonia and meningitis.

The natural antibiotic dermicidin, which is toxic to these bacteria, is found in human sweat. At least once a week, include high-intensity exercises in your workout, trying to work at 85% of your maximum capacity. And always use a clean towel.

7. MICROBE - BURNER Bifidobacterium animalis

® Lives in fermented milk products

Bifidobacterium animalis bacteria inhabit the contents of cans of yogurt, bottles of kefir, curdled milk, fermented baked milk and other similar products. They reduce the time of passage of food through the colon by 21%. Food does not stagnate, there is no formation of excess gases - you are less likely to experience the problem code-named "Feast of the Spirit."

Feed the bacteria, for example, with a banana - eat it after dinner. And for lunch itself, pasta with artichokes and garlic will go well. All these products are rich in fructooligos - saccharides - Bifidobacterium animalis loves this type of carbohydrate and eats them with pleasure, after which it multiplies with no less pleasure. And as the population grows, your chances of normal digestion increase.

We try to provide the most relevant and useful information for you and your health. The materials posted on this page are for informational purposes and are intended for educational purposes. Site visitors should not use them as medical advice. Determining the diagnosis and choosing a treatment method remains the exclusive prerogative of your doctor! We are not responsible for possible negative consequences resulting from the use of information posted on the website.