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

Over time, their structure became more complex, but to this day bacteria are considered the most primitive single-celled organisms. It is interesting that some bacteria still retain the primitive features of their ancient ancestors. This is observed in bacteria living in hot sulfur springs and anoxic mud at the bottom of reservoirs.

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

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

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

Body Shape

Bacteria are numerous and diverse organisms. They vary in shape.

Name of the bacterium	Bacteria shape	Bacteria image
Cocci		Ball-shaped
Bacillus		Rod-shaped
Vibrio		Comma-shaped
Spirillum		Spiral
Streptococci		Chain of cocci
Staphylococcus		Clusters of cocci
Diplococcus		Two round bacteria enclosed in one mucous capsule

Methods of transportation

Among bacteria there are mobile and immobile forms. Motiles move due to wave-like contractions or with the help of flagella (twisted helical threads), which consist of a special protein called flagellin. There may be one or more flagella. In some bacteria they are located at one end of the cell, in others - at two or over the entire surface.

But movement is also inherent in many other bacteria that lack flagella. Thus, bacteria covered on the outside with mucus are capable of gliding movement.

Some aquatic and soil bacteria lacking flagella have gas vacuoles in the cytoplasm. There may be 40-60 vacuoles in a cell. Each of them is filled with gas (presumably nitrogen). By regulating the amount of gas in the vacuoles, aquatic bacteria can sink into the water column or rise to its surface, and soil bacteria can move in the soil capillaries.

Habitat

Due to their simplicity of organization and unpretentiousness, bacteria are widespread 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 snow, desert sands, on the ocean floor, in oil extracted from great depths, and even in the water of hot springs with a temperature of about 80ºC. They live on plants, fruits, various animals and in humans in the intestines, oral cavity, limbs, and on the surface of the body.

Bacteria are the smallest and most numerous living creatures. Due to their small size, they easily penetrate into any cracks, crevices, or pores. Very hardy and adapted to various living conditions. They tolerate drying, extreme cold, and heating up to 90ºC without losing their viability.

There is practically no place on Earth where bacteria are not found, but in varying quantities. The living conditions of bacteria are varied. Some of them require atmospheric 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.

There are especially many of them in the soil. 1 g of soil can contain hundreds of millions of bacteria.

In water: in the surface layers of water in 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 absorb food, and synthesize vitamins.

External structure

The bacterial cell is covered with a special dense shell - a 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 wall of a plant cell. It is permeable: through it, nutrients freely pass into the cell, and metabolic products exit into the environment. Often, bacteria produce an additional protective layer of mucus on top of the cell wall - a capsule. The thickness of the capsule can be many times greater than the diameter of the cell itself, but it can also be very small. The capsule is not an essential part of the cell; it is formed depending on the conditions in which the bacteria find themselves. It protects the 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 there is dense, immobile cytoplasm. It has a layered structure, there are no vacuoles, therefore various proteins (enzymes) and reserve nutrients are located in the substance of the cytoplasm itself. Bacterial cells do not have a nucleus. A substance carrying hereditary information is concentrated in the central part of their cell. Bacteria, - nucleic acid - DNA. But this substance is not formed into a nucleus.

The internal organization of a bacterial cell is complex and has its own specific characteristics. The cytoplasm is separated from the cell wall by the cytoplasmic membrane. In the cytoplasm there is a 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). 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 is localized - DNA, which is not delimited from the cytoplasm by a membrane. This is an analogue of the nucleus - a nucleoid. The nucleoid does not have a membrane, a nucleolus, or a set of chromosomes.

Eating methods

Bacteria have different feeding methods. Among them there are autotrophs and heterotrophs. Autotrophs are organisms that are capable of independently producing organic substances for their nutrition.

Plants need nitrogen, but cannot absorb nitrogen from the air themselves. Some bacteria combine nitrogen molecules in the air with other molecules, resulting in substances that are 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 form on the roots of plants of the legume family and some other plants.

The roots provide carbohydrates to the bacteria, and the bacteria to the roots provide nitrogen-containing substances that can be absorbed by the plant. Their cohabitation is mutually beneficial.

Plant roots secrete a lot of 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 debris into plant-available substances. This layer of soil is called the rhizosphere.

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

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

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

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

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

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

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

Metabolism

Bacteria differ from each other in their metabolism. In some it occurs with the participation of oxygen, in others - without it.

Most bacteria feed on ready-made organic substances. Only a few of them (blue-green, or cyanobacteria) are capable of creating 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 into pieces, assemble their shell from these parts and replenish their contents (this is how they grow), and throw unnecessary molecules out. The shell and membrane of the bacterium allows it to absorb only the necessary substances.

If the shell and membrane of a 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. To survive, bacteria need a shell that allows necessary substances to pass through, but not unnecessary substances.

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

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

Bacteria, together with other groups of microorganisms, perform enormous chemical work. By converting various compounds, they receive the energy and nutrients necessary for their life. Metabolic processes, methods of obtaining energy and the need for materials for building the substances of their bodies are diverse in bacteria.

Other bacteria satisfy all their needs for carbon necessary for the synthesis of organic substances in the body at the expense of inorganic compounds. They are called autotrophs. Autotrophic bacteria are capable of synthesizing organic substances from inorganic ones. Among them are:

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 oxidize ammonia formed during the decay of organic residues to nitric acid. The latter reacts with mineral compounds of the soil, turning into salts of nitric acid. This process takes place in two phases.

Iron bacteria convert ferrous iron into oxide iron. The resulting iron hydroxide settles and forms the so-called bog iron ore.

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

A characteristic feature of hydrogen bacteria is the ability to switch to a heterotrophic lifestyle when provided with organic compounds and 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 in their bodies is broken down and releases 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 the hydrogen donor is hydrogen sulfide (occasionally carboxylic acids), and in green plants it is water. In both of them, the separation and transfer of hydrogen is carried out due to the energy of absorbed solar rays.

This 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:

6СО 2 +12Н 2 S+hv → С6Н 12 О 6 +12S=6Н 2 О

The biological significance of chemosynthesis and bacterial photosynthesis on a planetary scale is relatively small. Only chemosynthetic bacteria play a significant role in the process of sulfur cycling in nature. Absorbed by green plants in the form of sulfuric acid salts, sulfur is reduced 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), forming sulfites in the soil that are accessible to plants. Chemo- and photoautotrophic bacteria are essential in the nitrogen and sulfur cycle.

Sporulation

Spores form inside the bacterial cell. During the process of sporulation, the bacterial cell undergoes a number of biochemical processes. The amount of free water in it decreases and enzymatic activity decreases. This ensures the resistance of the spores to unfavorable environmental conditions (high temperature, high salt concentration, drying, etc.). Sporulation is characteristic of only a small group of bacteria.

Spores are an optional stage in the life cycle of bacteria. Sporulation begins only with a lack of nutrients or accumulation of metabolic products. Bacteria in the form of spores can remain dormant for a long time. Bacterial spores can withstand prolonged boiling and very long freezing. When favorable conditions occur, the spore germinates and becomes viable. Bacterial spores are an adaptation to survive in unfavorable 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 cell elongation, a transverse septum gradually forms, and then the daughter cells separate; In many bacteria, under certain conditions, after dividing, cells remain connected in characteristic groups. In this case, depending on the direction of the division plane and the number of divisions, different shapes arise. Reproduction by budding occurs as an exception in bacteria.

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 capable of forming a mass that can fill all seas and oceans. A simple calculation shows that 72 generations (720,000,000,000,000,000,000 cells) can be formed per day. If converted 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 to 65-100ºC, as a result of 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) find themselves attached to the wall of the bacterium and, as the bacterium elongates, move apart (5,6). First the nucleotide divides, then the cytoplasm.

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

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

The jumper transports DNA from one bacterium to another (3). Once in one bacterium, DNA molecules intertwine, stick together in some places (4), and then exchange sections (5).

The role of bacteria in nature

Gyre

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

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

Soil formation

Since bacteria are distributed almost everywhere and occur in huge numbers, they largely determine various processes occurring in nature. In autumn, the leaves of trees and shrubs fall, above-ground shoots of grasses die, old branches fall off, and from time to time the trunks of old trees fall. All this gradually turns into humus. In 1 cm3. 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 vital processes. These nitrogen-fixing bacteria live independently or settle in the roots of legume plants. Having penetrated the roots of legumes, these bacteria cause the growth of root cells and the formation of nodules on them.

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

Thanks to symbiosis with nodule bacteria, leguminous plants enrich the soil with nitrogen, helping to increase yield.

Distribution in nature

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

Soil microflora

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

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

The soil microflora is very diverse. Here there are different physiological groups of bacteria: putrefaction bacteria, nitrifying bacteria, nitrogen-fixing bacteria, sulfur bacteria, etc. among them there are aerobes and anaerobes, spore and non-spore forms. Microflora is one of the factors in 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 develop in large numbers. The bulk of them enters the water from the soil. A factor that determines the number of bacteria in water and the presence of nutrients in it. The cleanest waters are from artesian wells and springs. Open reservoirs and rivers are very rich in bacteria. The largest number of bacteria is found in the surface layers of water, closer to the shore. As you move away from the shore and increase in depth, the number of bacteria decreases.

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

In terms of species composition, the microflora of water is similar to the microflora of soil, but there are also specific forms. By destroying various waste that gets into the water, microorganisms gradually carry out the so-called biological purification of water.

Air microflora

The microflora of the air is less numerous than the microflora of soil and water. Bacteria rise into the air with dust, can remain there for some time, and then settle on 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 geographical zone, terrain, time of year, dust pollution, etc. each speck of dust is a carrier of microorganisms. Most bacteria are in the air above industrial enterprises. The air in rural areas is cleaner. The cleanest air is over forests, mountains, and snowy areas. The upper layers of air contain fewer microbes. The air microflora contains many pigmented and spore-bearing bacteria, which are more resistant than others to ultraviolet rays.

Microflora of the human body

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

The stomach has an acidic reaction, so the majority of microorganisms in it die. Starting from the small intestine, the reaction becomes alkaline, i.e. favorable for microbes. The microflora in the large intestines is very diverse. Each adult excretes about 18 billion bacteria daily in 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 of microbes. Microbes enter these organs only during illness.

Bacteria in the cycle of substances

Microorganisms in general and bacteria in particular play a large role in the biologically important cycles of substances on Earth, carrying out chemical transformations that are completely inaccessible to either plants or animals. Different stages of the cycle of elements are carried out by organisms of different types. The existence of each individual 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 primary role in supplying the necessary forms of nitrogen to organisms of the biosphere with different nutritional needs. Over 90% of total nitrogen fixation is due to the metabolic activity of certain bacteria.

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 complete oxidation of organic substances. Under aerobic conditions, organic compounds are initially broken down by fermentation, and the organic end products of fermentation are further oxidized by anaerobic respiration if inorganic hydrogen acceptors (nitrate, sulfate, or CO 2 ) are present.

Sulfur cycle

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

Iron cycle

Some freshwater bodies 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 bog iron ores and water sources rich in iron salts.

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

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

Biology teacher MBOU Secondary School No. 19 Natalia Vasilievna Shadrina Verkhnyaya Tura, Sverdlovsk region

Slide 2

General characteristics of bacteria

Bacteria are the most ancient group of organisms.

The first bacteria appeared more than 3.5 billion years ago. And they were the only living creatures on our planet. These are the first representatives of living nature; their body had a primitive structure. Bacteria are considered representatives of PROKARYOTES, because. do not have a core.

Slide 3

Structure of a bacterium

The cell wall performs a protective and supporting function Cytoplasm fills the space inside the cell Flagella or villi are organs of locomotion The outer shell or capsule protects DNA from drying out or the nuclear substance carries hereditary information The plasma membrane is permeable, metabolism occurs through it Conclusion: the bacterium does not have a separate nucleus

Slide 4

Bacteria are classified as prenuclear and separated into a separate kingdom.

• cyanobacteria
• bacteria
• multicellular
• unicellular
• higher
• inferior

Slide 7

Due to their simplicity of organization and unpretentiousness, bacteria are widespread in nature. Bacteria found everywhere

Habitats

Number of bacteria in 1cm3

The living conditions of bacteria are varied. Some of them require air oxygen (aerobes), others do not need it and are able to live in an oxygen-free environment (anaerobes)

Slide 8

Bacteria reproduction

1.Bacteria reproduce very easily. The mother cell divides in half. The result is two young bacterial cells.

2This happens extremely quickly. A bacterial cell is able to divide in 20 - 30 minutes.

3. If all the resulting bacteria “survived,” they would cover our planet with a thick layer... But most of them die before they can reproduce!

Slide 9

Education dispute

1. With a lack of nutrients or accumulation of metabolic products, sporulation occurs.

2. Spores can remain dormant for a long time.

3. Spores can withstand prolonged boiling and freezing.

4. When favorable conditions occur, the spore germinates and becomes viable.

CONCLUSION: Bacterial spores are an adaptation to survival in unfavorable conditions.

Slide 10

conclusions

1. Bacteria are the oldest group of living beings on the planet

2. The bacterial cell has a simple structure

3. It does not have a nucleus and the cytoplasm is motionless

4. Bacteria are classified as prenuclear organisms or prokaryotes

5. In unfavorable conditions they form spores

Project work passport.

Project name " Bacteria in our life"

The project manager is I.A. Shtreker, teacher of biology and chemistry of Municipal Budgetary Educational Institution Secondary School No. 24 of the village. Kaz.

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

Academic disciplines close to the topic of the project: history, computer science.

Age 13

Project type: Research

Target

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

Tasks

1.Study the effect of bacteria on dairy products;

2.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 lives.” I decided to make this presentation and defend it at a school environmental conference.

My work plan:

Selecting a topic.

Search for information

Study

Making a Presentation

5. Project protection.

What are microbes?! Where did they come from and what do they look like?! We hear on TV and 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 end up on objects, clothes, hands, and food. , in the mouth, intestines.

The sizes of microbes are so small that they are measured in thousandths and even millionths of a millimeter. Microbes can only be seen using an optical or electron microscope. They can cause various diseases and poisoning. 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 exist at all?!

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

Hypothesis: I want to make sure that there are bacteria on our hands. And is it really necessary to wash your hands to protect yourself from bacteria?

Relevance: Do bacteria exist on our hands?

Problem: ways to protect against bacteria.

History of discoveries

It became possible to see a microbe after the invention of the microscope. The first to see and describe microorganisms was the Dutch naturalist Antony van Leeuwenhoek (1632-1723), who constructed a microscope that provided magnification up to 300 times. Through a microscope, he examined everything that came to hand: pond water, various infusions, blood, dental plaque and much more. In the objects he examined, he discovered the smallest creatures, which he called “living animals.” He established spherical, rod-shaped and convoluted forms of microbes. Leeuwenhoek's discovery marked the beginning of the emergence of microbiology.

French chemist Louis Pasteur (1822-1895) was the first to study bacteria and their properties. He proved that microbes cause fermentation and decay and can cause disease.

I. I. Mechnikov (1845-1916) deserves great credit for the development of microbiology. It 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 study of the body's immunity to infectious diseases (immunity).

Habitat

Bacteria are the very first living creatures to appear on our planet.
Bacteria live almost everywhere there is water, including hot springs, the bottom of the world's oceans, and deep inside the earth's crust. They are an important link in 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. There are especially many of them in the soil. 1 gram of soil can contain hundreds of millions of bacteria.
The number of bacteria is different in the air of ventilated and unventilated rooms. So, in the classroom after ventilation before the start of the lesson there are 13 times less bacteria than before ventilation

1.3. What types of bacteria are there? Bacteria can be both beneficial and harmful.

For many animals, bacteria are simply necessary for life. 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 living in special parts of the stomach and intestines help animals digest fiber.

We know that putrefactive bacteria spoil food. But the harm they bring to humans is nothing compared to the benefits 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.

Curdled milk, cheese, sour cream, butter, kefir, sauerkraut, pickled vegetables - all these products would not exist if it were not for lactic acid bacteria. Man has been using them since ancient times. By the way, yogurt is absorbed 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.

Structure of bacteria

The structure depends on the way of life and food supply of the microorganism. Bacteria can have rod-shaped (bacilli), spherical (cocci) and spiral-shaped (spirilla, vibrio, spirochetes) shapes.

How they infect us? Contagious (infectious) diseases have been known since ancient times. The most severe of them (plague, cholera, smallpox) often spread massively and caused widespread pestilence, as a result of which flourishing cities turned into vast cemeteries.

In addition to these particularly dangerous infections, there are many other known infectious diseases that can cause epidemics - dysentery, typhoid and paratyphoid fever, typhus and relapsing fever, brucellosis, these diseases occur through dirty food 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 secreted by the sick body from the affected respiratory tract (nose, pharynx, bronchi, lungs). When a sick person speaks, coughs, or sneezes, he throws tiny sprays into the surrounding air - droplets of infected sputum or nasal mucus. In this way, pathogenic microbes easily penetrate along with contaminated air into the nose, pharynx, and lungs of healthy people, where the further development of the disease occurs. This “air” or “droplet” 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 about 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, did the students wash their hands?

Result:

When surveying 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 washed 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 to maintain your health.

My experiences.

I washed, peeled the potato tuber, cut it into 2 parts, soaked it in a soda solution, boiled it, cooled it. I made 2 glass jars with lids sterile, put a share of potatoes in the No. 1 jar with dirty hands, and a share of potatoes in the No. 2 jar with hands washed with soap. Placed the jars in a warm place. As a result, after 4 days, the potatoes that were taken with dirty hands were densely covered with colonies of bacteria, and in jar No. 2 the potatoes were partially covered with colonies.

Conclusion: dirty hands have a lot of bacteria.

Experiment No. 2 (with milk)

Making curdled milk from milk.

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

Making sour cream from cream.

I took 1 cup of cream and put it in a warm place, a day later it turned out to be sour cream

Conclusion: Thus, I was convinced that beneficial bacteria help make many delicious foods.

1. Introduction

2. Characteristics of bacteria

3. History of the discovery of microorganisms

4. Shapes of bacteria

5. Structure of bacteria

6. Spread of bacteria

7. Nutrition of bacteria

8. Reproduction of bacteria

9. Formation dispute

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). About 10,000 species of bacteria
• Bacteria are relatively simple microscopic single-celled organisms.
• divided by two departments: Crush and Cyanobacteria (Blue-green algae)

History of the discovery of bacteria

• The first person to see microorganisms was a Dutchman

Anthony van Leeuwenhoek:

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

Anthony van Leeuwenhoek

Characteristics of bacteria

• The most ancient 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)
• Have different handicaps
• Have different ways of feeding
• Distributed everywhere

Shapes of bacteria

Rod-shaped

Group name

Globular

Curved

tuberculosis

Spiral

vibrios

Spirilla

Spiral

Rod-shaped

Most bacteria are colorless.

Few are colored purple or green

spherical shape

Structure of bacteria

• Available dense cellular membrane covered on top with mucous membrane capsule
• Typical no kernel - there is nuclear matter, 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 cubic see water near cities contains up to 400,000 bacteria
• There are especially many bacteria in fertile soil, 1 cubic meter. cm soil more than a million bacteria

Nutrition of bacteria

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

- saprophytes

- symbionts

• Some bacteria are capable of creating organic substances themselves from inorganic ones - autotrophs:

- photoautotrophs ( cyanobacteria)

- chemoautotrophs

Metabolism:

• They live in an oxygen environment aerobes
• They live in an oxygen-free environment anaerobes

Bacteria reproduction

• They reproduce by dividing one cell into two (fragmentation)
• Under favorable conditions, the division process occurs every 20 - 30 minutes
• Restrains the growth of bacteria:

sunlight

Lack of food

Heat

Disinfectants

Interspecies fight

Stages of bacterial crushing

Education dispute

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

Bacterial spore formation

The role of bacteria in nature

• An important link in cycle of substances in nature
• Decompose complex substances to simple ones that use plants again
• Bacteria rotting decomposes the corpses of animals and dead plants , form humus - planetary orderlies

• Soil bacteria turn humus into minerals
• Nitrogen-fixing bacteria absorb nitrogen air, form nitrogen compounds in the soil (symbiosis with legumes

The role of bacteria in human life

• Infection occurs :

• when communicating with a patient,
• when consuming food or water with pathogenic bacteria
• unsanitary living conditions
• failure to comply with personal hygiene rules

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

• Used in Food Industry lactic acid bacteria
• They spoil food
• They spoil fishing nets, rare books, hay, etc.

• Cause disease person:

• typhoid, cholera, diphtheria, tetanus, tuberculosis, sore throat, meningitis, glanders, anthrax, brucellosis and other diseases

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

• Lack of core
• Absence of vacuole, chloroplasts
• The presence of flagella, which they need for movement
• Dense, cellulose-free casing

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

Lesson topic: Bacteria are the oldest group of living organisms.

General characteristics of bacteria.

Differences between bacterial cells and plant cells.

Lesson objectives:

educational: form the concept of bacteria as the oldest

group of living organisms;

developing: develop cognitive and creative activities

students; group work skills, logical

thinking;

educational: cultivate a culture of behavior in group and

individual work.

Lesson type: lesson explaining new material

Teaching methods: visual, partially exploratory, practical

Equipment: slide presentation, video clips “Rotting of fruits and vegetables”, “Invisible life”, virtual laboratory “Preparation of a microslide and examination of the bacterium Bacillus subtilis”

Didactic material: task cards, sheets with additional information

During the classes:

I. Organizing time

Set up for the lesson.

Greetings

Training "Hello!"

Students take turns touching the fingers of the same name on their neighbor’s hands, starting with the thumbs, and say:

I wish (thumbs touching);

success (index);

large (medium);

in everything (nameless);

and everywhere (little fingers);

Hello! (touch with whole palm)

Division into groups

Appointment of speakers, distribution of evaluation sheets.

IV. Preparation for active and conscious assimilation of new material

Strategy "Tree of Expectations" Students write down the expected results from the upcoming lesson on stickers and stick them to the tree.

Screening of the video clip “Rotting of Fruits and Vegetables”

Show a slide with different types of bacteria.

Question:

These small organisms created life on Earth, carry out the global cycle of substances in nature, and also serve humans.

Louis Pasteur called them “the great gravediggers of nature.” Who are they?

Name these small organisms.

Statement of the topic and objectives of the lesson.

V. Stage of learning new material

Screening of the video clip “Invisible Life”

If there were such a book of records of living organisms, then podium bacteria would come first.

Today you have to familiarize yourself with the topic. And determine for what achievements medals can be awarded to bacteria.

To make your work easier, I would like to present the first medal myself. Thismedal for antiquity .

You already know from the evolution section that the first living organisms appeared in water billions of years ago. And these were primitive organisms - bacteria. It was bacteria with chlorophyll that first saturated the Earth's atmosphere with oxygen and only then did the first plants appear. That's why we awarded the medal for antiquity.

Exercise: study §55 p.183 and additional information on the tables.

To get acquainted with the topic, 5-7 minutes are provided. Time managers control time. After studying the topic, each team will have to present a medal to the bacteria and explain for what merit this medal was awarded.

Physical education minute

VI. Checking your understanding of new material

Students fill out an answer sheet with tasks (+, -)

	Do you believe that...
	Bacteria nuclear organisms
	Aerobic and anaerobic respiration
	The discoverer of the bacterium, Anthony van Leeuwenhoek
Right answers:		Peer assessment:

Evaluation criterion:

9-10 points “5”

7-8 points “4”

5-6 points "3"

VII. Topic consolidation stage

Laboratory work No. 30“Examination of the appearance of Bacillus subtilis”

Goal: to verify the structural features of the Bacillus subtilis bacterium.

Virtual laboratory “Preparation of a microslide and examination of the bacterium Bacillus subtilis”

http://biolicey2vrn.ru/index/bakterija_sennaja_palochka/0-474

Conclusions for the lesson

1. Bacteria are primitive single-celled organisms that are microscopic in size.

2. Bacteria are ubiquitous.

3. They reproduce very quickly under favorable conditions.

4. A spore is a bacterial cell with a dense shell.

5. They feed in an autotrophic and heterotrophic way.

6. They breathe aerobically and anaerobically.

VIII. Lesson summary

Reflection

Strategy "Tree of Expectations" Students whose expectations were met at the end of the lesson remove their stickers from the “expectation tree” and read them out.

Grading a lesson

Homework information

Study §55.

Prepare messages on the topics: “Painful bacteria”, “Nodule bacteria”, “Lactic acid bacteria”.

Assessment sheet

Student's full name		"Mnemonics"		Self-assessment	Teacher rating	final grade

Assessment sheet

Class________ Team______________

Student's full name	Evaluation when compiling a medal	"Mnemonics"	Blitz poll “Do you believe that...”	Self-assessment	Teacher rating	final grade

Bacteria.

There is practically no place on earth where bacteria are not found. These are the most ancient creatures on earth, which appeared about three and a half billion years ago. For comparison: the earth arose four billion years ago, and the universe fourteen, humanity several tens of thousands of years ago. There are especially many bacteria in the soil; one gram of soil can contain hundreds of millions of bacteria.

Bacteria are the smallest creatures on the ground. Scientists know about 10,000 species of bacteria. They can only be examined under a microscope, because... their sizes are very small and they are colorless. The cells of living organisms are approximately the same size, and the cells of bacteria are ten times smaller than the cells of other organisms. Even the largest ones do not exceed 0.01 microns, but most are much smaller.

When studying bacteria under a microscope, scientists noticed that bacteria are not just similar to each other, they have the ability to have several external appearances, that is forms bacteria.

Shape of bacteria.

spherical (cocci)

rod-shaped (bacillus)

convoluted (vibrios)

similar to a spiral (spirilla)

spirochetes (6-10 turns)

streptococci (chain of cocci)

staphylococci (clusters of cocci)

The simplest form of bacteria is a ball, it is called coccus, which translated means “berry”. When multiplying, cocci sometimes remain connected in pairs, such a connection is called diplococcus, with a larger amount a chain is formed, which is called streptococcus. When cocci are connected in clusters, they get the name staphylococcus. Cocci that have an elongated shape are called sticks, if they have a curved shape, then they are called vibrio. Spiral-shaped long bacteria are called - spirilla or spirochete. There are other forms, but these are the most important.

The shape determines the abilities of bacteria such as attachment to the surface, mobility, and absorption of nutrients. In addition, bacteria can live in colonies.

Bacteria

History of the study of bacteria.

The Dutch naturalist Antonie van Leeuwenhoek first saw bacteria in an optical microscope in 1676 and called them “animalcules.”

Christian Ehrenberg coined the name “bacteria” in 1828.

Louis Pasteur in the 1850s initiated the study of the physiology and metabolism of bacteria, and also discovered their pathogenic properties.

Robert Koch formulated the general principles for identifying the causative agent of a disease. In 1905 he was awarded the Nobel Prize for his research into tuberculosis.

M.V. Beyerinck and S.N.Vinogradsky laid the foundations of general microbiology and the study of the role of bacteria in nature.

Bacteria very prolific . Reproduce bacteria dividing one cell into two. Under favorable conditions, cell division in many bacteria can occur every 20-30 minutes. With such rapid reproduction, the offspring of one bacterium in 5 days is capable of forming a mass that could fill all the seas and oceans. However, this does not happen in nature, since most bacteria quickly die under the influence of sunlight, drying, lack of food, etc.

In order to tolerate unfavorable conditions, bacteria have learned to form disputes – special forms of bacteria. They are formed when the bacteria inside its shell dries out, decreasing in size. In this case, the contents of the cell, shrinking, move away from the shell, become rounded and form on its surface, being inside the mother shell, a new, denser shell. Spores (from the Greek word "spore" - seed) of some bacteria persist for a very long time in the most unfavorable conditions. They can withstand drying, heat and frost, and do not immediately die even in boiling water. Spores are easily spread by wind, water, etc. There are many of them in the air and soil. Under favorable conditions, the spore germinates and becomes a living bacterium. Bacterial spores are an adaptation to survive in unfavorable conditions.

Bacteria

The living conditions of bacteria are very diverse.

Type breathing among bacteria there are aerobes and anaerobes .

Like all living things, most bacteria require oxygen. However, there are bacteria that can live without oxygen. Once in an environment where there is a lot of oxygen, they die. Under natural conditions, bacteria that require oxygen live on the surface of the soil, in the upper layers of water, and in the atmospheric air. Those bacteria for which oxygen is destructive live in the deep layers of the soil, in silt, and in the water column.

Bacteria

The life activity of bacteria can occur in different temperature conditions. Some of them are able to develop under temperature conditions from -2 to +75 degrees. Bacteria can live in places where virtually nothing can survive: boiling geysers, underground oil lakes, acid lakes where there are no fish. Some bacteria can survive even in space. But the most favorable temperature for most bacteria can be considered from +4 to +40 degrees. At higher temperatures, many types of bacteria die. To destroy bacteria, they are exposed to steam at a temperature of 120 degrees for 20 minutes. Sun rays are also harmful to bacteria.

The structure of a bacterium. Each bacterium is just one cell with a thin membrane and cytoplasm.

A bacterium, like any cell, is covered cell membrane, on top of the cell membrane there is a special protective shell - cell wall, which is made from a special substance - murein. The liquid part of the cell is called cytoplasm. Bacteria prokaryotes , they do not have a nucleus, instead there is a clot of cytoplasm in which there is a molecule that carries information - a DNA molecule, and is called nucleoid, translated as "core-like". Flagellum bacteria are necessary for movement, but not all bacteria have a flagellum, and not all of them are capable of movement. Not all bacteria have special villi(bacilli are covered with hairs - pili), of which there are two types: some of which attach the bacterium to the necessary surfaces, others serve to transmit information between bacteria. Inside the bacterium is storage nutrient. Both the cell wall and the cell membrane are permeable to substances that bacteria need for life, primarily for nutrition. When harmful substances for bacteria are formed, they are also removed through the shell and membrane, which is how bacteria metabolize.

Blitz poll “Do you believe that” (+, -).

	Do you believe that...
	Bacteria are ubiquitous
	Divided into three groups based on shape
	Spherical bacteria - cocci
	Bacteria nuclear organisms
	Autotrophic and heterotrophic mode of nutrition
	Form spores during reproduction
	The hereditary substance is located in the nucleus
	Aerobic and anaerobic respiration
	The science that studies bacteria - microbiology
Right answers:		Peer assessment:

Blitz poll “Do you believe that” (+, -).

	Do you believe that...
	Bacteria are ubiquitous
	Divided into three groups based on shape
	Spherical bacteria - cocci
	Bacteria nuclear organisms
	Autotrophic and heterotrophic mode of nutrition
	Form spores during reproduction
	The hereditary substance is located in the nucleus
	Aerobic and anaerobic respiration
	The science that studies bacteria - microbiology
	Discoverer of the bacterium, Anthony van Leevehoek
Right answers:		Peer assessment:

Blitz poll “Do you believe that” (+, -).

	Do you believe that...
	Bacteria are ubiquitous
	Divided into three groups based on shape
	Spherical bacteria - cocci
	Bacteria nuclear organisms
	Autotrophic and heterotrophic mode of nutrition
	Form spores during reproduction
	The hereditary substance is located in the nucleus
	Aerobic and anaerobic respiration
	The science that studies bacteria - microbiology
	Discoverer of the bacterium, Anthony van Leevehoek
Right answers:		Peer assessment:

Blitz poll “Do you believe that”

Students fill out an answer sheet with tasks (+, -).

	Do you believe that...
	Bacteria are ubiquitous
	Divided into three groups based on shape
	Spherical bacteria - cocci
	Bacteria nuclear organisms
	Autotrophic and heterotrophic mode of nutrition
	Form spores during reproduction
	The hereditary substance is located in the nucleus
	Aerobic and anaerobic respiration
	The science that studies bacteria - microbiology
	Discoverer of the bacterium, Anthony van Leevehoek
Right answers:		Peer assessment:

Reception "Mnemotechnics" Expressions on the topic are read out, students do not write anything down. After this, students reproduce them from memory in their notebooks. At the end, the winner is revealed, the one who remembers the most words.

Strateria "Traffic Light" formative assessment.

Green card - satisfied with myself, I did everything in my power and even more

Yellow card – could have done better

Red card – I’m not happy, I didn’t do everything I could.