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.

§ The Earth's atmosphere is an illuminated, dynamic, well-mixed environment with short-term residence of various components and fast transport systems.

Layers of the atmosphere Stratosphere Tropopause 1) Convection layer - 10 km 2) Transitional, or outer layer of free turbulence - 500 - 1000 m Troposphere 3) Turbulent boundary layer 10 -500 m 4) Local vortex layer - 2 - 10 m 5) Laminar boundary layer 1 mm – 2 m

Composition of gases in the air Methane (CH 4) – is formed by methanogens and destroyed by methylotrophs. Oxide and nitrous oxide, nitrogen (NO 2, NO, N) - is formed by nitrifiers, destroyed by denitrifiers. Carbon monoxide (CO 2) - is formed during respiration, oxidation of organic compounds, fires, and is used in photosynthesis and chemosythesis Sulfur dioxide (SO 2) - is formed by sulfur bacteria and during the combustion of sulfur-containing fuels Oxygen and hydrogen

The main source of greenhouse gases on Earth is the activity of microorganisms. Anthropogenic activity only increases the imbalance in the atmosphere by 510%, which contributes to the climate system going out of balance.

Microorganisms in the air are found in three main phases of the bacterial aerosol: Droplet, or large-nuclear phase (consists of bacterial cells surrounded by a water-salt shell. Particle diameter is about 0.1 mm or more). Fine-nuclear phase (formed when the particles of the first phase dry out and consists of bacterial cells that retain only chemically bound water on their surface and free water inside the cells, the diameter of most particles does not exceed 0.05 mm). “Bacterial dust” phase (From the first two phases, bacteria can transform into larger particles that settle as dust on various objects. The particle size varies from 0.01 to 1 mm)

Sanitary microbiological study of air Sedimentation method Based on the sedimentation of bacterial particles and droplets in 515 minutes under the influence of gravity on the agar surface of open Petri dishes A x 100 X = ---- 75 cm 2 Aspiration method Based on the forced sedimentation of microorganisms on the surface of a dense nutrient medium or into the collection liquid. Using the Krotov apparatus

Criteria for assessing the air of residential premises Air assessment Total number of bacteria in 1 m 3 Number of streptococci Summer clean polluted up to 1500 to 2500 up to 16 to 36 Winter clean polluted up to 4500 to 7000 up to 36 to 124

Air disinfection is carried out: with gases (phenol, C 5 H 6 O 3); aerosol (formalin with creolin); UFL; removing air (ventilation); the use of air ionizers.

The quantitative and qualitative composition of the microflora of the atmospheric air depends on the nature of the soil and water cover, the general sanitary condition of the area, seasonal, climatic and meteorological factors (intensity of solar radiation, temperature, precipitation, etc.).

Number of microorganisms in the air Locality Number of microbes in 1 m 3 Air above the taiga, sea 1 -10 air in cities 4000- 9800 park air 175- 345 air in animal premises 12000- 86000

Aquatic ecosystems include: Oceans, seas Lakes Rivers Groundwater Amphibious landscapes, ecotones Swamps

Depending on the biological consumption of oxygen and the concentration of organic matter, water bodies are distinguished by the degree of trophy: Oligotrophic - 50 ∙ 103 bacterial cells per 1 ml (Lake Baikal, Ladoga) Mesotrophic - 1000 ∙ 103 bacterial cells per 1 ml (ponds) Eutrophic - 2000 - 10000 ∙ 103 bacterial cells per 1 ml (rivers) Dystrophic – 1000 – 2000 ∙ 103 bacterial cells per 1 ml (swamps)

Factors influencing the life activity of microorganisms Temperature Salt composition of water Dissolved gases Water acidity Oxidation reduction potential Bottom sediments

Characteristics of aquatic microorganisms Allochthonous (coming from outside) (pathogenic, lactic acid, etc.) Autochthonous (natives) (cyanobacteria, gliding bacteria, sulfur, methanogens, methylotrophs,

Sanitary microbiological examination of water Determination of bacteria of the Enterobacteriaceae family Membrane filter method. The required volume of water - 300 ml - is filtered through 100 ml membrane filters. The filters are transferred to Endo medium in a Petri dish and incubated at 37 ° C for 24 hours. The number of red and metallic red colonies is counted. Identification of bacteria is carried out using the oxidase test and the test for the formation of acid and gas during the fermentation of lactose (mannitol) Titration method. The principle of the method is to inoculate 333 ml of water - 3 volumes of 100 ml, 3 volumes of 10 ml, 3 volumes of 1 ml - into lactose-peptone (or glucose-peptone) medium, followed by re-seeding into Endo medium and culture identification

Determination of spores of sulfite-reducing bacteria Membrane filter method. The method is based on filtering water through membrane filters, growing crops in iron sulfite agar under anaerobic conditions and counting black colonies. The results of the analysis are expressed as the number of colony-forming units (CFU) of sulfite-reducing clostridia spores in 20 ml of water. Direct sowing method. Inoculate 20 ml of water into test tubes with iron sulfite agar (2 volumes of 10 ml in 2 test tubes or 4 volumes of 5 ml in 4 test tubes), incubate at 44 ° C for 24 hours and count the black colonies. The results are expressed as the number of CFU in 20 ml of water.

Determination of coliphages Direct method. The test water is added to 5 sterile cups of 20 ml each. In the 6th - control water is not taken. Then melted and cooled to 45 ° agar with the addition of a daily culture of E. coli is poured into all cups. Mix, leave to harden and incubate at 37 ° C for 24 hours. The result is taken into account by counting plaques in Petri dishes in PFU (plaque-forming units) in 100 ml of water. There should be no plaques in the control plate. Titration method. The method is based on preliminary growing of coliphages in an enrichment medium in the presence of E. coli and subsequent detection of coliphage plaques on the E. coli lawn.

Drinking water quality standards Units of measurement Standards 1. Total microbial number of CFU in 1 ml of water No more than 50 2. Bacteria of the Enterobacteriaceae family Number of intestinal bacteria in 300 ml of water Absence 3. Thermotolerant coliform bacteria Number of intestinal bacteria in 300 ml of water Absence 4. Spores sulfite-reducing clostridia Number of spores in 20 ml of water Absence 5. Coliphages Number of PFU in 100 ml of water Absence Indicators

Microorganisms have completely populated our planet. They are everywhere - in water, on land, in the air, they are not afraid of high and low temperatures, the presence or absence of oxygen or light, high concentrations of salts or acids are not critical. Bacteria survive everywhere. And yet, if water and soil as habitats are the most favorable, then viruses and bacteria in the air do not live very long.

How do bacteria end up in the air?

While bacteria live in soil and water, they are present in the air. This environment is not capable of providing normal life activity for microorganisms, since it does not contain nutrients, and the UV radiation of the Sun often leads to the death of bacteria.

The movement of air from the surface lifts dust and microscopic particles of matter along with the microorganisms they contain - this is how bacteria end up in the air. They move with air currents and eventually settle to the ground.

Since microbes rise from the surface, the bacterial contamination of the airspace, both qualitatively and quantitatively, directly depends on the microbiological saturation of the surface layer.

The higher the air layer is located from the surface of the planet, the fewer microorganisms it contains. But they exist. Bacteria in the airspace were found even in the stratosphere, at an altitude of more than 23 km from the surface, where the air layer is extremely thin and the impact of cosmic rays is very severe and is not contained by the atmosphere.

A bacterial sample at an altitude of 500 m above the surface in a large city is quantitatively thousands of times higher than an air sample in a high mountain region or above the water surface far from the coast.

What bacteria can be in the air

Since bacteria do not live in the air, but are only transported by wind currents, there is no need to talk about any typical representatives of bacteria.

There can be a variety of types of bacteria in the air, which react differently to being in such an unfavorable environment for them:

• cannot withstand dehydration and die quickly;
• go into the spore phase and wait out critical conditions for life for months.

For humans, the presence of pathogenic microorganisms in the air is essential, including:

• plague bacillus (the causative agent of bubonic and septic plague, plague pneumonia);
• Bordet-Gengou bacteria (the causative agent of whooping cough);
• Koch's bacillus (the causative agent of tuberculosis);
• Vibrio cholerae (the causative agent of cholera).

Almost all of the listed bacteria, when released into the air, die quickly enough, but there are also such as Koch’s bacillus (tuberculosis), an acid-resistant spore-forming bacterium that remains viable even in dry dust for up to 3 months.

The presence of infectious disease agents in the air increases the risk of infection for an individual, as well as the occurrence of an epidemic when a large group of people is exposed to infection.

Bacteria can be transmitted not only through dry particles in the wind

When a patient coughs or sneezes, droplets of sputum released into the air, containing a large number of bacteria that cause the disease. If droplets of sputum containing pathogenic bacteria come into contact with a healthy person, they are likely to cause infection. This method of transmission of infectious diseases is called airborne.

Pathogenic bacteria that cause infectious diseases and are transmitted almost exclusively by air include:

• flu;
• scarlet fever;
• smallpox;
• diphtheria;
• measles;
• tuberculosis.

Differences in bacterial composition of air

It is natural that the air in different places has its own characteristics, depending on many factors. If this is an enclosed space, then the following factors have a great influence on the level of bacterial contamination of the space:

• the specifics of the use of the room - it could be a bedroom, work area, pharmaceutical laboratory, etc.;
• carrying out ventilation;
• compliance with sanitary and hygienic standards in the premises;
• planned implementation of measures to clean the indoor air from bacteria.

Bacterial contamination in places associated with long-term stay of large masses of people, such as train stations, subway stations and cars, hospitals, kindergartens, etc., is characterized by the highest rates.

To assess the level of quantity and composition of bacteria, sanitary and hygienic standards applicable to any enclosed space are used:

• apartments;
• work areas;
• medical hospitals;
• any public places.

For indoor air, viridans streptococci and staphylococci are considered to be sanitary indicator microorganisms, and the presence of hemolytic streptococci in the sample indicates the threat of an epidemic.

The quantitative and qualitative bacteriological composition of air masses both in the open air and in enclosed spaces (apartments, work areas, etc.) is not a static value, but varies depending on the time of year, with minimum values ​​in winter and maximum values ​​in summer.

Air purity is assessed according to SanPin 2.1.3.1375-03 by the number of microorganisms determined in the volume of air; most often, the sample is tied to 1 m 3 of the air being tested.

Methods for purifying air from germs

According to studies, the air in apartments or work areas is many times dirtier and more toxic than outside. This is due to the presence in the air, in addition to microbes, viruses, mold and fungal spores, household or industrial dust, pet hair, tobacco smoke, volatile chemical compounds (furniture, flooring, household chemicals, etc.) and much more.

To clean the air from bacteria, you can use various methods, but first of all you need to get rid of dirt and dust - it is with them that microorganisms enter the air.

Wet cleaning and vacuuming as methods of air purification

Household and industrial dust affects the human body as a strong allergen; with the slightest movement of air, it moves from place to place, and with it bacteria.

The most reliable way to get rid of dust and the bacteria it contains is to carry out wet cleaning using disinfectants. Moreover, this procedure must be carried out regularly.

You can remove dust from surfaces with a vacuum cleaner - they clean floors and floor coverings quite well. However, there is no guarantee of complete removal of caked dust; a higher level of cleanliness can be achieved with a modern washing vacuum cleaner with HEPA filters.

Carpets in apartments should be taken outside and beaten out - this is a long-known way to get rid of accumulated dust.

Ventilation to purify the air

An effective method of cleaning the air from dust and bacteria both in apartments and in work areas is to ventilate the room. It is most effective to carry it out early in the morning and late in the evening (at home - before bed).

Air purifiers

These devices are designed to purify the air in living quarters and work areas from air pollutants. A filtration method is used where airborne dust, harmful substances and bacteria remain on the filter.

The quality of air purification directly depends on the type of filter used.

Air purifier filters are divided into:

• mechanical – remove only large-sized contaminants from the air;
• coal - quite effective, but cannot be used to purify air at high humidity;
• HEPA filters are modern, highly efficient filters; retain all impurities, including bacteria and their spores; As an additional plus, they humidify the air in the room.

Humidifiers

In addition to cleanliness, the air must have a certain level of humidity - if the air in living quarters and work areas is dry, moisture from the skin will saturate the air. Which naturally leads to drying of the skin and mucous membranes, the formation of microcracks, which will reduce the antibacterial and antiviral resistance of the body.

The optimal level of indoor air humidity is the range of 35-50%:

• for humans – the most comfortable humidity;
• for bacteria – a zone of development inhibition.

Humidifiers are used to maintain optimal humidity levels in work areas and living areas.

Depending on the type, humidifiers are:

• ultrasonic;
• traditional;
• direct spray;
• steam generators.

To decide which humidifier to use in each specific case, you should know their advantages and disadvantages.

Brief overview of humidifier characteristics

1.Ultrasonic humidifiers.

Pros: economical in cost and energy consumption, during operation they create little noise (fan).

Cons: use of distillate; no automatic water filling; the threat of microflora developing in the container (most often legionella) with its subsequent release into the air, the need for regular disinfection of the container; short service life.

2. Traditional – cold evaporation humidifiers.

Pros: low cost, purifies room air, uses tap water.

Disadvantages: it is noisy, requires regular cleaning and disinfection, there is a danger of the development of pathogenic microflora and its release into the room air, high wear and tear.

3. Direct spray humidifiers.

High-class equipment with virtually no shortcomings. The disadvantages include the high cost and the need for professional installation.

4. Humidifiers - steam generators.

Pros: average cost, disinfection of water by boiling.

Disadvantages: very energy-intensive, large in size, noisy in operation, require frequent maintenance, direct steam output is a potential danger.

Humidifiers of any type solve the problem of cleaning the air from dust and bacteria in a work area or living space; you just need to determine how many and which humidifiers are optimal in a particular case.

The role of green spaces

The cleaner the air in places of public and personal use, the less it contains various bacteria, including pathogenic ones.

The importance of green spaces in air purification cannot be overestimated - plants deposit dust, and the phytoncides they secrete kill microbes.

Plants in the apartment

Indoor plants in residential and work areas perform the function of a biological filter - they absorb harmful substances from the air, collect dust on the leaves, humidify the air, release oxygen and phytoncides that kill pathogenic bacteria.

Common antiseptic plants for home air purification:

• geranium;
• aloe;
• begonia;
• myrtle;
• rosemary.

The average radius of the antibacterial effect of the plant is about 3 m; in addition, the plants deodorize the air and have a tonic effect.

Outdoor plants purify the air

Trees and shrubs in the open air constantly clean the air space from both mechanical impurities and toxins, and pathogenic microorganisms. Plants release volatile phytoncides that kill bacteria.

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The atmosphere is one of the most important components of our planet. It is she who “shelters” people from the harsh conditions of outer space, such as solar radiation and space debris. However, many facts about the atmosphere are unknown to most people.

1. True color of the sky

Although it's hard to believe, the sky is actually purple. When light enters the atmosphere, air and water particles absorb the light, scattering it. At the same time, the violet color scatters the most, which is why people see a blue sky.

2. An exclusive element in the Earth's atmosphere

As many remember from school, the Earth's atmosphere consists of approximately 78% nitrogen, 21% oxygen and small amounts of argon, carbon dioxide and other gases. But few people know that our atmosphere is the only one so far discovered by scientists (besides comet 67P) that has free oxygen. Because oxygen is a highly reactive gas, it often reacts with other chemicals in space. Its pure form on Earth makes the planet habitable.

3. White stripe in the sky

Surely, some people have sometimes wondered why a white stripe remains in the sky behind a jet plane. These white trails, known as contrails, form when hot, humid exhaust gases from a plane's engine mix with cooler outside air. Water vapor from the exhaust freezes and becomes visible.

4. Main layers of the atmosphere

The Earth's atmosphere consists of five main layers, which make life on the planet possible. The first of these, the troposphere, extends from sea level to an altitude of about 17 km at the equator. Most weather events occur here.

5. Ozone layer

The next layer of the atmosphere, the stratosphere, reaches an altitude of approximately 50 km at the equator. It contains the ozone layer, which protects people from dangerous ultraviolet rays. Even though this layer is above the troposphere, it may actually be warmer due to the energy absorbed from the sun's rays. Most jet planes and weather balloons fly in the stratosphere. Airplanes can fly faster in it because they are less affected by gravity and friction. Weather balloons can provide a better picture of storms, most of which occur lower in the troposphere.

6. Mesosphere

The mesosphere is the middle layer, extending to a height of 85 km above the surface of the planet. Its temperature hovers around -120 °C. Most meteors that enter the Earth's atmosphere burn up in the mesosphere. The last two layers that extend into space are the thermosphere and exosphere.

7. Disappearance of the atmosphere

The Earth most likely lost its atmosphere several times. When the planet was covered in oceans of magma, massive interstellar objects crashed into it. These impacts, which also formed the Moon, may have formed the planet's atmosphere for the first time.

8. If there were no atmospheric gases...

Without the various gases in the atmosphere, the Earth would be too cold for human existence. Water vapor, carbon dioxide and other atmospheric gases absorb heat from the sun and “distribute” it across the planet's surface, helping to create a habitable climate.

9. Formation of the ozone layer

The notorious (and essential) ozone layer was created when oxygen atoms reacted with ultraviolet light from the sun to form ozone. It is ozone that absorbs most of the harmful radiation from the sun. Despite its importance, the ozone layer was formed relatively recently after enough life arose in the oceans to release into the atmosphere the amount of oxygen needed to create a minimum concentration of ozone

10. Ionosphere

The ionosphere is so called because high-energy particles from space and the sun help form ions, creating an "electric layer" around the planet. When there were no satellites, this layer helped reflect radio waves.

11. Acid rain

Acid rain, which destroys entire forests and devastates aquatic ecosystems, forms in the atmosphere when sulfur dioxide or nitrogen oxide particles mix with water vapor and fall to the ground as rain. These chemical compounds are also found in nature: sulfur dioxide is produced during volcanic eruptions, and nitrogen oxide is produced during lightning strikes.

12. Lightning power

Lightning is so powerful that just one bolt can heat the surrounding air up to 30,000°C. The rapid heating causes an explosive expansion of nearby air, which is heard as a sound wave called thunder.

Aurora Borealis and Aurora Australis (northern and southern auroras) are caused by ion reactions occurring in the fourth level of the atmosphere, the thermosphere. When highly charged particles from the solar wind collide with air molecules above the planet's magnetic poles, they glow and create dazzling light shows.

14. Sunsets

Sunsets often look like the sky is on fire as small atmospheric particles scatter the light, reflecting it in orange and yellow hues. The same principle underlies the formation of rainbows.

In 2013, scientists discovered that tiny microbes can survive many kilometers above the Earth's surface. At an altitude of 8-15 km above the planet, microbes were discovered that destroy organic chemicals and float in the atmosphere, “feeding” on them.

Adherents of the theory of the apocalypse and various other horror stories will be interested in learning about.

Microscopic living organisms, the tiniest on the planet, the most numerous inhabitants of the Earth are bacteria. These are creatures, at least amazing, arousing the interest of science since they were finally noticed by humanity with the invention of multiple magnification of objects (microscope). Before this, the evolution of bacteria took place in people, one might say, “under our very noses,” but no one paid enough attention to them. And completely in vain!

Antiquity of origin

They are the most ancient inhabitants of our planet. The long-standing habitat of bacteria is the Earth. Bacteria were the first living organisms to appear here, according to some scientists, about three and a half billion years ago (for comparison, the age of the Earth is about four billion). That is, roughly speaking, the age of bacteria is comparable to the age of the nature around us. By the way, the known history of mankind goes back only a few tens of thousands of years. We are so “young” compared to these microorganisms.

The smallest and most numerous

Bacteria are also the smallest known living species. The fact is that the cells of almost all living organisms have approximately the same size. But not bacterial cells. The average one is about ten times smaller in size than the average cell, for example, a human cell. Because they are so tiny, they are also the most numerous inhabitants. It is known that a lump of soil where bacteria live can contain as many inhabitants as, for example, people in all European countries.

Endurance

Nature, when creating bacteria, invested in them a huge margin of strength, significantly exceeding the endurance of other representatives of the fauna. Since the times of “deep antiquity”, many cataclysms have occurred on Earth, and bacteria have learned to withstand them. To this day, the habitat of bacteria is so diverse that it arouses deep interest among microbiologists. Microorganisms can sometimes be found in places where certainly no other creature can live.

Where can bacteria live?

For example, in boiling geysers, where the water temperature can reach almost a hundred degrees above zero. Or - in underground oil lakes, as well as in acidic lakes unsuitable for life, where any fish or other animal would immediately dissolve - this is where bacteria can live.

Scientists suggest that some may even exist in space! By the way, one of the versions of the settlement of the globe with living beings, the theory of the origin of life on the planet, is based on these data.

Controversy

To survive such unfavorable conditions, some bacteria form spores. We can say that this is a special, sleeping, resting form. Before forming a spore, the bacterium begins to dry out, removing liquid from itself. It decreases in size, remaining inside its shell, and is additionally covered with another shell - of a protective nature. In this form, a microorganism can exist for a very, very long time, thus, as it were, “waiting out” difficult times. Then, depending on the environment in which the bacteria live - favorable or not - they can resume their vital functions in full. This unique ability to survive in adverse conditions is being carefully studied by microbiologists.

Ubiquitous

To the question “where do bacteria live?” You can answer very simply: “Almost everywhere!” Namely: around us and in us, in the atmosphere, in the soil, in the water. And every person comes into contact with myriads of these creatures every day, without noticing it. Among them there are pathogenic and opportunistic bacteria. There are also completely safe for the human body.

On the ground

The soil where bacteria live contains the greatest amount of them. There are nutrients necessary for life and the optimal amount of water; there is no direct sunlight. Most of these bacteria are saprophytes. They participate in the formation of the fertile part of the soil (humus). However, pathogenic microorganisms are also present here: the causative agents of tetanus, botulism, gas gangrene and other diseases. They can then enter the air and water, further infecting humans with these diseases.

Thus, the causative agent of tetanus, a rather large rod, enters the body from the soil during various skin lesions and multiplies in anaerobic (without oxygen) conditions.

In water

Another place where bacteria can live is in an aquatic environment. They get here when they are washed away from the soil and runoff ends up in water bodies. For this reason, by the way, there are much fewer bacteria in artesian water than in ground water. And ordinary water from a lake or river can become an environment where pathogenic bacteria live, a place for the spread of many dangerous diseases: typhoid fever, cholera, dysentery and some others. For example, dysentery is caused by bacteria from Shigella species and is accompanied by severe intoxication of the body and damage to the gastrointestinal tract.

In the atmosphere

There are not as many of them in the air where bacteria can live as in the soil. The atmosphere is an intermediate stage in the migration of microorganisms, and therefore cannot serve - due to the lack of nutrients and insufficient humidity - as a permanent habitat for bacteria. Bacteria enter the air with dust and microscopic droplets of water, but then eventually settle on the soil. However, in densely populated areas - large cities, for example - the number of microorganisms contained in the air can be large, especially in the summer. And the air itself can serve as an environment where all kinds of infections live. Some of them: diphtheria, whooping cough. And also tuberculosis caused by

On a person

There are a great variety of microorganisms on human skin. But they are unevenly distributed over the entire plane. Bacteria have “favorite” places, and there are areas that resemble deserted deserts. Moreover, according to scientists, most microorganisms that live on human skin are not harmful. On the contrary, they perform a kind of protective function for humans from microbes considered dangerous. It has been scientifically proven that excessive sterility and cleanliness are not so good (of course, no one has yet canceled the simple ones). The least amount of bacteria is found in humans. The main amount is on the forearms (there are up to 45 species there). Many bacteria live on the mucous membranes, the so-called wet areas, where they feel very comfortable. In dry ones (palms, buttocks) - the living conditions are not entirely suitable for microorganisms.

Inside us

According to microbiologists, approximately three kilograms of bacteria live in it! And in quantitative terms, this is a huge army that cannot be ignored. However, bacteria are smart neighbors. The bulk of those living in the human body (as well as other mammals) are useful and maintain a peaceful neighborhood with their “masters.” Some help digestion. Others perform security functions: as a result of their actions, pathogenic microorganisms that attempt to enter the protected territory are immediately destroyed. 99% of the population are bifidobacteria and bacteroides. And enterococci, Escherichia coli (which is conditionally pathogenic), lactobacilli - approximately from 1 to 10%. Under unfavorable conditions, they can cause various diseases, but in the body of a healthy person they perform useful functions. Various fungi and staphylococci also live there, which can also be pathogenic. But basically, in the gastrointestinal tract there is a certain bacteriological balance, as if intended by nature, which maintains human health at the proper level. And with a sufficiently high immunity, they cannot penetrate inside and cause harm.