Bacteria - a general characteristic. Classification, structure, nutrition and role of bacteria in nature. Bacteria are the oldest organisms on Earth Biology Project Bacteria are the oldest form of organisms

1. Introduction

2. Characterization of bacteria

3. History of the discovery of microorganisms

4. Forms of bacteria

5. The structure of bacteria

6. Spread of bacteria

7. Feeding Bacteria

8. Reproduction of bacteria

9. Spore formation

10. The role of bacteria in nature

11. The role of bacteria in human life

12. List the differences in the structure of a bacterial cell from a plant cell?

Introduction

• The science that studies bacteria is called bacteriology (microbiology). known about 10,000 types of bacteria
• Bacteria are relatively simple microscopic unicellular organisms.
• divided by two departments: Drobyanki and Cyanobacteria (Blue-green algae)

History of the discovery of bacteria

• The first person to see microorganisms was a Dutchman

Anthony van Leeuwenhoek:

“April 24, 1676, I looked at the water ... and with great surprise I saw in it a huge number of the smallest living creatures ...”

Anthony van Leeuwenhoek

Characterization of bacteria

• The oldest organisms on Earth, the first appeared about 3.5 billion years ago
• unicellular organisms
• microscopically small
• Bacteria do not have a nucleus prokaryotes - pre-nuclear)
• They have a different shape
• Have different ways of eating
• Distributed everywhere

Shapes of bacteria

rod-shaped

Group name

spherical

curved

tuberculosis

Spiral

vibrios

Spirilla

Spiral

rod-shaped

Most bacteria are colorless.

Few are colored purple or green

spherical shape

The structure of bacteria

• Available dense cellular membrane covered with mucous membrane capsule
• typical no core - there is a nuclear substance, non-nuclear
• Majority has flagella
• Can have inclusion with a supply of nutrients

Spread of bacteria

• Distributed everywhere:

In the air

in living organisms

• In 1 cu. see water near cities has up to 400,000 bacteria
• There are especially many bacteria in fertile soil, in 1 cu. see soil over a million bacteria

Bacteria nutrition

• Most bacteria feed on ready-made organic substances - heterotrophs:

- saprophytes

- symbionts

• Some bacteria are able to create organic substances from inorganic ones - autotrophs:

- photoautotrophs ( cyanobacteria)

- chemoautotrophs

Metabolism:

• Live in an oxygen environment aerobes
• In anoxic - live anaerobes

Reproduction of bacteria

• Reproduce by dividing one cell into two (fragmentation)
• Under favorable conditions, the division process occurs every 20 to 30 minutes.
• Restrain the growth of bacteria:

sunlight

Lack of food

Heat

Disinfectants

Interspecies struggle

Stages of crushing bacteria

Spore formation

• Under unfavorable conditions, the bacterium turns into a spore
• The dispute persists for a very long time
• In the form of a spore, bacteria can be spread by wind, water
• Once in favorable conditions, spores germinate and become viable bacteria.

Formation of bacterial spores

The role of bacteria in nature

• An important link in matter cycle in nature
• Break down complex substances into simple ones, which are again used by plants
• bacteria rotting decompose the corpses of animals and dead plants , form humus - orderlies of the planet

• soil bacteria turn humus into minerals
• nitrogen fixing bacteria absorb nitrogen air, form nitrogen compounds in the soil (symbiosis with leguminous plants

The role of bacteria in human life

• Infection occurs :

• when interacting with patients,
• when eating food or water with pathogenic bacteria
• unsanitary living conditions
• non-compliance with the rules of personal hygiene

• Mass disease of people - epidemic
• Patients receive medicine , and in the premises they carry out disinfection

• Use in Food Industry lactic acid bacteria
• Spoil food
• Spoil fishing nets, rare books, hay, etc.

• Cause disease person:

• typhus, cholera, diphtheria, tetanus, tuberculosis, tonsillitis, meningitis, glanders, anthrax, brucellosis and other diseases

List the differences in the structure of a bacterial cell from a plant cell?

• No core
• Absence of vacuoles, chloroplasts
• The presence of flagella necessary for them to move
• Tough, cellulose-free casing

• Pasechnik V.V. Biology. Textbook. 6 cells
• Korchagina V.A. Biology. Textbook. 6 cells
• Serebryakova T.I. Biology. Textbook. 6 cells

Archeology and history are two sciences that are closely intertwined. Archaeological research provides an opportunity to learn about the past of the planet, which, through history, is built in chronological order. Scientists engaged in such research are constantly striving to find more and more ancient forms of living beings that lived on Earth. Studies have shown that bacteria are the oldest microorganisms that ever inhabited the planet.

These microorganisms are constantly under scrutiny, as their role in the process of evolution is almost impossible to overestimate. Discussions on this topic arise very often, but as a result it always turns out that bacteria live on the planet much longer than other creatures, which there are numerous confirmations.

The process of studying bacteria is actively going on, almost no research is being done, and each new discovery becomes a sensation for the whole world. One of the brightest events was the discovery of anaerobic sulfur bacteria that existed 3.4 billion years ago in Australia. The discovery caused a lot of controversy and discussion: even theories about the unearthly origin of microorganisms were used.

There are other types of creatures that can survive for an extremely long time. A good example is certain groups of cyanobacteria, whose age often reaches 2 billion years. Such bacteria are one of the persistent forms of life - creatures capable of evolving without significant changes in their organisms.

Archaeologists manage to find a lot of unique remains of microorganisms, one way or another involved in the process of evolution. Fossil algae and microbes found in the rocks of South Africa were among the oldest organisms: there were found the remains of protozoan bacteria and blue-green algae that existed at least 3.2 billion years ago. This discovery was incredibly important for the scientific community, since these microorganisms were marine, which suggests that the water area was already home to microbes, which later transformed into algae, plants and living beings.

Another important stage in the study of ancient bacteria was the study of groups of microorganisms discovered during excavations in Ontario. The study of the remains showed that these microorganisms existed already two billion years ago. These bacteria were also among the most primitive microorganisms and have already been included in the corresponding section of the taxonomy.

Not so ancient creatures are of considerable interest for history. So, in the central part of Australia, the remains of microorganisms that are part of multicellular algae and other plants were found. The age of these bacteria is within one billion years. The discovery of such units of microorganisms has become very important: based on their research, scientists can restore the chronology of the evolution of the past and supplement the systematics.

The oldest bacteria existed not only in a single-celled form, but were also part of more complex organisms, for example, green algae, capable of reproducing sexually. Each discovery of this magnitude provides more and more opportunities in the study of living beings, since a variety of forms of organisms that lived in nature arise: any new unit always adds another touch to the genetic diversity of living beings.

The final transition to the differentiation of multicellular creatures occurred about 600 million years ago. Scientists believe that the cause of development was the emergence of various forms of reproduction and the appearance of the first animals, as a result of which nature began to evolve much faster.

Classification and structure of bacteria

In the process of evolution, a large number of the most diverse bacteria appeared. The classification of various microorganisms is carried out by biological systematics, which determines:

• the name of a particular type of microorganism;
• the position of the bacterial species in the general classification;
• characteristic features of different types of microorganisms.

The structure of bacteria suggests the presence of a hard shell that can preserve the shape of the body and the insides of microorganisms. The shape of the shell is one of the main points that make it possible to classify bacteria: there are spherical, rod-shaped, spiral-shaped and other shapes. Microorganisms are also evaluated by their size: the largest representatives can reach 0.75 mm in length, and the dimensions of the smallest are measured in fractions of micrometers.

The most advanced bacteria have developed flagella that provide movement in space. To improve motor functions, certain types of bacteria stretched into a filamentous form. About flagellated organisms can be said separately. The main difference between flagellar protozoa and bacteria is the presence of a nucleus in the former. In addition, these microorganisms have chromatophores that allow them to paint themselves in different colors, thereby acquiring similarities with various algae. The main pigment is chlorophyll, which provides the creature's green color, but it is not uncommon to combine with other pigments.

Since external factors can cause the death of primitive bacteria, many of them have developed a protective function - the formation of spores. When a bacterium is destroyed or its life cycle is terminated, the spores leave the shell and settle in the available space. The production of spores has become an extremely convenient mechanism for most bacteria, since spores perfectly withstand most of the aggressive influences, including temperature shock, lack of liquid or food.

The diversity of bacterial species is amazing: the number of studied species reaches several tens of thousands, which is only a small part of the microorganisms that existed on Earth. A certain difficulty in the study of bacteria is the fact that they are found in almost all multicellular organisms, including algae, terrestrial plants and animals.

The role of bacteria and their development in the life of the planet

The search for the oldest, primordial microorganisms is a very problematic task. From many species of bacteria, practically nothing remains for many millions of years, and they have to be studied based on modern species of living beings, which significantly complicates the systematics. Of course, high-quality equipment and leading minds of specialists allow us to learn a lot, but still, sometimes research runs into an impenetrable wall of time. That is why the number of studied living organisms does not exceed a certain value: there is not enough data for taxonomy.

• temperature;
• pressure;
• wind movement;
• other physical and chemical processes.

Nevertheless, according to individual ancient layers, scientists manage to establish many aspects associated with certain organisms. Having certain data on bacteria, algae and other structures that appeared later, one can draw conclusions about the earliest creatures and supplement the systematics.

It is known for certain that the very first organisms required nutrition, therefore they ate organic matter. Over the past millions of years, a large number of microorganism species have changed, and the most persistent subsequently became the basis for the formation of bacteria. Some of them managed to reach the present day almost unchanged. The key feature that provided ancient microorganisms with such high survivability is their ability to absorb nutrients from almost any substance - earth, water, air, etc. Further evolution forced bacteria to develop, as a result of which types of microorganisms appeared that feed on fermentation, decay and other factors.

The most ancient microorganisms originated and developed in water, since such an environment was the most comfortable for them. This partly explains the diversity of different algae: initially, bacteria were combined into similar multicellular structures. This trend was characterized by almost the entire Precambrian era. Gradually, the smallest organisms united into multicellular organisms, and over time they came to land, which is the reason for the development of terrestrial nature. It is to bacteria that the world can owe its development and constant evolution aimed at adapting to new conditions in a constantly changing world.

Conclusion

Science is constantly moving forward, allowing you to study more and more new types of organisms. In the past there were a lot of different bacteria and microorganisms, and scientists are working hard, finding more and more ancient evidence of the life of certain life forms: the remains of any microorganism, whether it be an algae or a complex multicellular organism, are of great value.

The role of these studies is quite high: at some point, science will be able to get to the deepest historical and earthly layers, which will make it possible to learn more about the development of nature on the planet. Bacteria are the oldest microorganisms on the planet, and they can provide a clue to the origin of life, such a discovery will be incredibly important for every person.

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 disease. Symbiotic live in the digestive organs, helping to break down and assimilate food, synthesize vitamins.

External structure

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

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

Internal structure

Inside the bacterial cell is a dense immobile cytoplasm. It has a layered structure, there are no vacuoles, 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, thus 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. 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 is part of the 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.

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

reproduction

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

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

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

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

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

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

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

The role of bacteria in nature

Circulation

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

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

soil formation

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

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

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

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

Distribution in nature

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

Soil microflora

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

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

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

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

Microflora of reservoirs

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

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

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

Air microflora

Air microflora is less numerous than soil and water microflora. Bacteria rise into the air with dust, can stay there for a while, and then settle to the surface of the earth and die from lack of nutrition or under the influence of ultraviolet rays. The number of microorganisms in the air depends on the geographic area, 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.

Bacteria is the most ancient organism on earth, as well as the simplest in its structure. It consists of only one cell, which can only be seen and studied under a microscope. A characteristic feature of bacteria is the absence of a nucleus, which is why bacteria are classified as prokaryotes.

Some species form small groups of cells; such clusters may be surrounded by a capsule (sheath). The size, shape, and color of bacteria are highly dependent on the environment.

In terms of shape, bacteria are divided into: rod-shaped (bacilli), spherical (cocci) and convoluted (spirilla). There are also modified ones - cubic, C-shaped, star-shaped. Their sizes range from 1 to 10 microns. Certain types of bacteria can actively move with the help of flagella. The latter sometimes exceed the size of the bacterium itself twice.

Types of bacteria forms

For movement, bacteria use flagella, the number of which is different - one, a pair, a bundle of flagella. The location of the flagella is also different - on one side of the cell, on the sides, or evenly distributed over the entire plane. Also, one of the ways of movement is considered to be sliding due to the mucus that the prokaryote is covered with. Most have vacuoles inside the cytoplasm. Adjusting the capacity of the gas in the vacuoles helps them move up or down in the liquid, as well as move through the air channels of the soil.

Scientists have discovered more than 10 thousand varieties of bacteria, but according to the assumptions of scientific researchers, there are more than a million species of them in the world. The general characteristics of bacteria makes it possible to determine their role in the biosphere, as well as to study the structure, types and classification of the bacterial kingdom.

habitats

The simplicity of the structure and the speed of adaptation to environmental conditions helped bacteria to spread over a wide range of our planet. They exist everywhere: water, soil, air, living organisms - all this is the most acceptable habitat for prokaryotes.

Bacteria have been found both at the south pole and in geysers. They are on the ocean floor, as well as in the upper layers of the Earth's air shell. Bacteria live everywhere, but their number depends on favorable conditions. For example, a large number of bacterial species live in open water bodies, as well as in the soil.

Structural features

A bacterial cell is distinguished not only by the fact that it does not have a nucleus, but also by the absence of mitochondria and plastids. The DNA of this prokaryote is located in a special nuclear zone and has the form of a nucleoid closed in a ring. In bacteria, the cell structure consists of a cell wall, a capsule, a capsule-like membrane, flagella, pili, and a cytoplasmic membrane. The internal structure is formed by the cytoplasm, granules, mesosomes, ribosomes, plasmids, inclusions and nucleoid.

The bacterial cell wall performs the function of defense and support. Substances can freely flow through it due to permeability. This shell contains pectin and hemicellulose. Some bacteria secrete a special mucus that can help protect against drying out. Mucus forms a capsule - a polysaccharide in chemical composition. In this form, the bacterium is able to tolerate even very high temperatures. It also performs other functions, for example, sticking to any surfaces.

On the surface of the bacterial cell are thin protein villi - pili. There may be a large number of them. Pili help the cell to transfer genetic material, and also provide adhesion to other cells.

Under the plane of the wall is a three-layer cytoplasmic membrane. It guarantees the transport of substances, and also plays a significant role in the formation of spores.

The cytoplasm of bacteria is 75 percent made from water. The composition of the cytoplasm:

• fishsomes;
• mesosomes;
• amino acids;
• enzymes;
• pigments;
• sugar;
• granules and inclusions;
• nucleoid.

Metabolism in prokaryotes is possible, both with the participation of oxygen and without it. Most of them feed on ready-made nutrients of organic origin. Very few species are capable of synthesizing organic substances from inorganic ones themselves. These are blue-green bacteria and cyanobacteria, which played a significant role in shaping the atmosphere and saturating it with oxygen.

reproduction

In conditions favorable for reproduction, it is carried out by budding or vegetatively. Asexual reproduction occurs in the following sequence:

1. The bacterial cell reaches its maximum volume and contains the necessary supply of nutrients.
2. The cell lengthens, a partition appears in the middle.
3. Within the cell, a division of the nucleotide occurs.
4. DNA main and separated diverge.
5. The cell is divided in half.
6. Residual formation of daughter cells.

With this method of reproduction, there is no exchange of genetic information, so all daughter cells will be an exact copy of the mother.

The process of reproduction of bacteria in adverse conditions is more interesting. Scientists learned about the ability of bacteria to reproduce sexually relatively recently - in 1946. Bacteria do not have a division into female and germ cells. But they have different DNA. Two such cells, when approaching each other, form a channel for the transfer of DNA, an exchange of sites occurs - recombination. The process is quite long, the result of which are two completely new individuals.

Most bacteria are very difficult to see under a microscope because they do not have their own color. Few varieties are purple or green due to their content of bacteriochlorophyll and bacteriopurpurine. Although if we consider some colonies of bacteria, it becomes clear that they release colored substances into the environment and acquire a bright color. In order to study prokaryotes in more detail, they are stained.

Classification

The classification of bacteria can be based on indicators such as:

• Form
• way to travel;
• way to get energy;
• waste products;
• degree of danger.

Bacteria symbionts live in partnership with other organisms.

Bacteria saprophytes live on already dead organisms, products and organic waste. They contribute to the processes of decay and fermentation.

Decay cleanses nature of corpses and other wastes of organic origin. Without the process of decay, there would be no cycle of substances in nature. So what is the role of bacteria in the cycling of matter?

Decay bacteria are an assistant in the process of breaking down protein compounds, as well as fats and other compounds containing nitrogen. Having carried out a complex chemical reaction, they break bonds between the molecules of organic organisms and capture protein molecules, amino acids. Splitting, the molecules release ammonia, hydrogen sulfide and other harmful substances. They are poisonous and can cause poisoning in humans and animals.

Decay bacteria multiply rapidly in favorable conditions for them. Since these are not only beneficial bacteria, but also harmful ones, in order to prevent premature decay in products, people have learned to process them: dry, pickle, salt, smoke. All of these treatments kill bacteria and prevent them from multiplying.

Fermentation bacteria with the help of enzymes are able to break down carbohydrates. People noticed this ability in ancient times and use such bacteria to make lactic acid products, vinegars, and other food products to this day.

Bacteria, working in conjunction with other organisms, do very important chemical work. It is very important to know what types of bacteria are and what benefits or harm they bring to nature.

Significance in nature and for man

The great importance of many types of bacteria (in the processes of putrefaction and various types of fermentation) has already been noted above; fulfillment of a sanitary role on Earth.

Bacteria also play a huge role in the cycle of carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, calcium and other elements. Many types of bacteria contribute to the active fixation of atmospheric nitrogen and convert it into an organic form, contributing to an increase in soil fertility. Of particular importance are those bacteria that decompose cellulose, which are the main source of carbon for the vital activity of soil microorganisms.

Sulfate-reducing bacteria are involved in the formation of oil and hydrogen sulfide in therapeutic mud, soils and seas. Thus, the layer of water saturated with hydrogen sulfide in the Black Sea is the result of the vital activity of sulfate-reducing bacteria. The activity of these bacteria in soils leads to the formation of soda and soda salinization of the soil. Sulfate-reducing bacteria convert nutrients in rice plantation soils into a form that becomes available to the roots of the crop. These bacteria can cause corrosion of metal underground and underwater structures.

Thanks to the vital activity of bacteria, the soil is freed from many products and harmful organisms and saturated with valuable nutrients. Bactericidal preparations are successfully used to combat many types of insect pests (corn borer, etc.).

Many types of bacteria are used in various industries to produce acetone, ethyl and butyl alcohols, acetic acid, enzymes, hormones, vitamins, antibiotics, protein and vitamin preparations, etc.

Without bacteria, processes are impossible in tanning leather, drying tobacco leaves, making silk, rubber, processing cocoa, coffee, urinating hemp, flax and other bast-fiber plants, sauerkraut, sewage treatment, leaching metals, etc.

Passport of project work.

Project name " Bacteria in our life

Project leader - I.A. Shtreker, teacher of biology and chemistry, MBOU secondary school No. 24, town. Kaz.

The subject of study is biology, within which the work is carried out.

Academic disciplines are close to the topic of the project: history, informatics.

Age 13

Project Type: Research

Target

Empirically confirm the importance of our living conditions for the growth and development of bacteria.

Tasks

1. To study the effect of bacteria on dairy products;

2. To study methods of combating pathogenic bacteria;

3. Study hygiene rules.

I, Maria Zhuravleva, decided to investigate the effect of bacteria on milk and potatoes and make a presentation on the topic "Bacteria in our life." I decided to make this presentation and defend it at a school environmental conference.

My work plan:

Topic selection.

Search for information

Study

Making a presentation

5. Protection of the project.

What are microbes?! Where did they come from and what do they look like? We hear on TV and on the radio, read in newspapers and on the Internet that bacteria and microbes are harmful organisms and they live in the environment around us - air, soil, water - from where they then get on objects, clothes, hands, food , in the mouth, intestines.

The size of microbes is so small that they are measured in thousandths and even millionths of a millimeter. Microbes can only be seen with an optical or electron microscope. They can cause various diseases, poisonings. Therefore, it is necessary to comply with sanitary and hygienic requirements.

There are a huge number of microbes, but which ones live in us ?! How do they differ and do they even exist?

In total, scientists counted 500 species of bacteria in the samples.

Hypothesis: I want to make sure there are bacteria on our hands. And do you really need to wash your hands to protect yourself from bacteria?

Relevance: Do bacteria exist on our hands?

Problem: ways to protect against bacteria.

Discovery history

Seeing the microbe became possible after the invention of the microscope. The first to see and describe microorganisms was the Dutch naturalist Anthony van Leeuwenhoek (1632-1723), who designed a microscope that magnified up to 300 times. Through a microscope, he examined everything that came to hand: water from a pond, various infusions, blood, plaque, and much more. In the objects he viewed, he found the smallest creatures, which he called "living animals". He established spherical, rod-shaped and convoluted forms of microbes. Leeuwenhoek's discovery laid the foundation for the emergence of microbiology.

The French chemist Louis Pasteur (1822-1895) was the first to study bacteria and their properties. He proved that microbes are the cause of fermentation and decay, capable of causing disease.

Great merit in the development of microbiology II Mechnikov (1845-1916). He also identified human diseases caused by bacteria. He organized the first bacteriological station in Russia. The name of Mechnikov is associated with the development of a new direction in microbiology - immunology - the doctrine of the body's immunity to infectious diseases (immunity).

Habitat

Bacteria are the very first living things that appeared on our planet.
Bacteria live almost everywhere where there is water, including hot springs, the bottom of the world's oceans, and also deep inside the earth's crust. They are an important link in the metabolism in ecosystems.

There is practically no place on Earth where bacteria are found. They live in the ice of Antarctica at a temperature of -83 Celsius and in hot springs (volcano or desert), where the temperature reaches +85 or +90 Celsius. Especially a lot of them in the soil. One gram of soil can contain hundreds of millions of bacteria.
The number of bacteria is different in the air of ventilated and unventilated rooms. So, in the classroom after airing before the start of the lesson, bacteria are 13 times less than before airing.

1.3. What are bacteria. Bacteria are both beneficial and harmful.

Many animals need bacteria to live. For example, plants are known to serve as food for ungulates and rodents. The bulk of any plant is fiber (cellulose). But it turns out that bacteria that live in special sections of the stomach and intestines help animals digest fiber.

We know putrefactive bacteria spoil food. But this harm that they bring to man is nothing compared to the benefits that they bring to nature as a whole. These bacteria can be called "natural orderlies". By decomposing proteins and amino acids, they support the cycle of substances in nature.

Yogurt, cheese, sour cream, butter, kefir, sauerkraut, pickled vegetables - all these products would not exist if there were no lactic acid bacteria. Man has been using them since ancient times. By the way, curdled milk is digested three times faster than milk - in an hour the body completely digests 90% of this product. Without lactic acid bacteria, there would be no silage for livestock feed.

The structure of bacteria

The structure depends on the mode of life and nutrition of the microorganism. Bacteria can be rod-shaped (bacilli), spherical (cocci) and spiral (spirilla, vibrios, spirochetes) shape.

How do they infect us?? Contagious (infectious) diseases have been known since ancient times. The most severe of them (plague, cholera, smallpox) often took on a mass distribution, caused a wholesale pestilence, as a result of which flourishing cities turned into vast cemeteries.

In addition to these especially dangerous infections, there are still many other infectious diseases that can cause epidemics - these are dysentery, typhoid fever and paratyphoid fever, typhus and relapsing fever, brucellosis, these diseases arise through dirty products and hands. The method of infection is the transfer of the pathogen into the respiratory tract through the air around us. The causative agents of many infectious diseases are excreted by a sick organism from the affected respiratory tract (nose, pharynx, bronchi, lungs). When a sick person speaks, coughs, sneezes, he throws out the smallest splashes into the surrounding air - droplets of infected sputum or nasal mucus. In this way, pathogenic microbes easily penetrate, together with contaminated air, into the nose, throat, and lungs of healthy people, where the further development of the disease occurs. Such an "air" or "drip" path of movement of infectious microbes is observed when healthy people are infected with influenza, scarlet fever, measles, diphtheria, whooping cough, smallpox, and mumps.

Survey-observation.

I interviewed 20 people how they wash their hands before eating, 19 people know that they need to wash their hands with soap before eating - this is 98% of students. After the work done, I was interested in the question: “How often do students wash their hands before eating?”. During the break, I began to observe at the entrance to the dining room, do the students wash their hands?

Result:

When asked students, “Do they know that it is necessary to wash their hands before eating?”, 98% of students answered that they know and understand why this is necessary.

Having observed the schoolchildren at the entrance to the dining room, I found out that about 8 people wash their hands without soap before eating, and 12 people did not wash their hands.

Conclusion: it is not enough to know, you also need to apply knowledge in order to maintain your health.

My experiences.

I washed, peeled the potato tuber, cut it into 2 shares, soaked it in a soda solution, cooked it, cooled it. I made 2 glass jars with lids sterile, put the potato share in jar No. 1 with dirty hands, and the potato share in No. 2 jar washed with soapy hands. Banks put in a warm place. As a result, after 4 days, the potatoes that I took with dirty hands were densely covered with bacterial colonies, and in jar No. 2, the potatoes were partially covered with colonies.

Conclusion: there are a lot of bacteria on dirty hands.

Experience No. 2 (with milk)

Obtaining curdled milk from milk.

I took 1 glass of fresh milk, put it in a warm place the next day I got yogurt

Getting sour cream from cream.

I took 1 glass of cream and put it in a warm place, a day later I got sour cream

Conclusion: In this way, I was convinced that beneficial bacteria help make many delicious foods.