Start in science. Chapter I. Review of sources of information on the research problem. Preparation of nutrient medium

Air, soil and water are possible sources of contamination of food by microorganisms, as well as contamination of food and people by pathogenic microbes. In this regard, water has a special important. IN food industry and in public catering establishments it is used for washing processed food raw materials, equipment, and is directly included in many products. Naturally, the water used must meet certain sanitary and hygienic standards.

AIR MICROBIOLOGY

Microorganisms enter the atmospheric air mainly from the soil, as well as from plants, animals, and people. Microorganisms are usually found in the air along with dust particles and in tiny suspended droplets of moisture.

Air is not a favorable environment for the development of microorganisms, since there is no droplet-liquid water in it. In the air, microorganisms can retain their viability only temporarily, and many die more or less quickly under the influence of drying and solar radiation.

Air microflora is diverse in quantity and composition and can vary significantly depending on climatic conditions, time of year, general sanitary condition of the area and other factors. Over the seas, mountains, and ice fields of the Arctic, the air contains very few microbes (units per 1 m3). There are much more of them in the air of populated areas, especially large industrial cities.

As you move away from populated areas, the number of microorganisms in the air decreases noticeably, but viable microorganisms have been found even in the stratosphere, although there are very few of them there. There are significantly fewer microbes in the air in winter than in summer.

Green spaces are of great importance in reducing the number of microbes in the air. The leaves of trees and shrubs have a significant dust-retaining ability -

ness. In addition, plant phytoncides have a detrimental effect on microorganisms. According to Ya. G. Kishko, in the center of Lviv the number of bacteria in 1 m 3 of air is about 3000, inside the city park – 1000, and inside the country park – 500.

The composition of air microflora is unstable. The air usually contains various micrococci, sarcina, spore-forming and non-spore-forming rod-shaped bacteria, fungal spores, yeast; Pathogenic microorganisms may also be present. Some pathogens are transmitted through the air infectious diseases(tuberculosis, staphylococcal and streptococcal influenza infections, etc.), which are released by patients and bacilli carriers when talking, sneezing, coughing.

The number of microorganisms in the air of working and living spaces depends on their sanitary and hygienic condition. When there are crowds of people, poor ventilation, or improper cleaning of premises, the number of microorganisms in the air increases.

At food industry enterprises, in production workshops and in food storage areas, it is necessary to maintain not only a certain humidity and air temperature, but also its cleanliness. Should not be allowed in the surrounding area or in utility rooms trade and catering establishments have accumulations of all kinds of waste.

Sanitary assessment of indoor air is carried out according to two microbiological indicators: total number bacteria and the number of sanitary indicator microorganisms in 1 m 3 of air. Sanitary indicator microorganisms are hemolytic (dissolving red blood cells) streptococci and staphylococci. They are permanent inhabitants of the upper respiratory tract, nasal mucosa and oral cavity of humans. The air in food production workshops should contain no more than 100–500 bacteria per 1 m 3, depending on the nature of production.

As indicative criteria, it is believed possible (A.I. Shafir) to recognize the air of residential premises as clean when there are up to 1500 bacteria and 16 streptococci in 1 m 3; contaminated - at 2500/m 3 of all bacteria and 38 streptococci. The air in refrigeration chambers is examined for contamination with mold spores (see p. 197).

Timely painting, whitewashing of walls, ceilings, systematic wet cleaning premises and ventilation significantly reduce the dust content of the premises and the number of microbes in them.

In some cases, the air supplied to the room (food storage rooms, etc.) is passed through special filters that retain microorganisms; Air disinfection is also sometimes used. Only those disinfectants that quickly cause hygiene are suitable for this purpose.

white microorganisms, are harmless to humans, do not damage equipment and other objects, are colorless and odorless. Disinfectants are used in the form of evaporation or mechanical spraying.

Ultraviolet irradiation and ozonation are used to disinfect the air in some production workshops, medical rooms and refrigeration chambers.

SOIL MICROBIOLOGY

Soil is the natural habitat of microorganisms. They find in the soil all the conditions necessary for their development, food, moisture, protection from the harmful effects of direct sun rays and drying.

Soil microflora in terms of quantitative and species composition varies significantly depending on chemical composition soil, its physical properties, reaction (pH), moisture capacity, degree of aeration. Climatic conditions, time of year, methods of agricultural tillage, and the nature of vegetation cover and other factors.

Microorganisms are also unequally distributed across soil horizons. The smallest of them are usually found in the very surface layer of soil, a few millimeters thick, where microorganisms are exposed to the adverse effects of sunlight and drying. The next layer of soil up to 5–10 cm thick is especially abundantly populated with microorganisms. As you go deeper, the number of microorganisms decreases. At a depth of 25–30 cm, their number is 10–20 times less than in the surface layer 1–2 cm thick (according to A. S. Razumov).

The composition of the microflora also changes with depth. In the upper layers of soil, which contain a lot of organic matter and are subject to good aeration, aerobic saprophytes predominate, capable of decomposing complex organic compounds. The deeper the soil horizons, the poorer they are in organic matter; air access to them is difficult, so anaerobic bacteria predominate there.

The soil microflora is represented by various types of bacteria, actinomycetes, fungi, algae and protozoa.

The permanent inhabitants of the soil include various putrefactive, mainly spore-bearing, aerobic (Bacillus subtilis, B. cereus var. mycoides, B. megaterium) and anaerobic (Clostridium sporogenes, CI. putrificum) bacteria, as well as bacteria that decompose fiber, nitrifying, denitrifying, nitrogen-fixing, sulfur and iron bacteria.

The activity of soil microorganisms plays a big role in creating soil fertility. Consistently replacing each other, microorganisms carry out processes in a circular manner.

a variety of substances in the soil. Organic substances that enter the soil in the form of plant remains, animal corpses and other contaminants are gradually mineralized. Compounds of carbon, nitrogen, phosphorus and other elements are converted from forms inaccessible to plants into substances assimilated by them.

Along with the usual inhabitants of the soil, there are also pathogenic microorganisms, mainly spore-forming bacteria, for example, the causative agents of tetanus, gas gangrene, botulism, etc. Therefore, contamination of food products with soil is dangerous.

When assessing soil sanitary conditions, the criterion is the titer of E. coli and the number of saprophytic bacteria. It is also advisable to define CI. perfringens and enterococci.

WATER MICROBIOLOGY

Natural waters, like soil, are the natural habitat of many microorganisms, where they are able to live, reproduce, and participate in the processes of cycling carbon, nitrogen, sulfur, iron and other elements. Quantitative and ka-

|the natural composition of the microflora of natural waters is varied. Groundwater. The composition of the microflora of groundwater (artesian, spring, groundwater) mainly depends on the depth of the aquifer and its protection from contamination from the outside. Artesian waters, located at great depths, contain very few microorganisms. Groundwater, extracted through conventional wells from shallow aquifers into which surface contaminants can seep, contains significant amounts of bacteria, some of which may be pathogenic. The closer to the surface they are located groundwater, the more abundant their microflora.

Surface waters. These are the waters of open reservoirs (rivers, lakes, reservoirs, etc.). They are distinguished by a wide variety of the composition of their microflora, depending on the chemical composition of the water, the nature of the use of the reservoir, the population of coastal areas, the time of year, meteorological and other conditions. In addition to our own aquatic microorganisms, many microorganisms from the outside enter open water bodies.

In a river, for example, flowing in the area of large settlements or industrial enterprises, water can contain hundreds of thousands and millions of bacteria in 1 cm 3, and above these points there are only hundreds or thousands of bacteria.

There are more microorganisms in the water of the coastal zone of reservoirs, especially standing ones, than far from the shores. More microorganisms are also found in the surface layers of water, but there are especially many of them in silt, mainly in its upper layer, where a film of bacteria is formed, which plays a large role in the processes of transformation of substances in a reservoir. The number of bacteria in open water bodies increases significantly during spring floods or after heavy rains.

The chemical composition of water and its microflora change especially when domestic and industrial wastewater is introduced into the reservoir. Along with various organic and mineral contaminants, a mass of microorganisms are introduced into the reservoir, “among which pathogenic ones can also enter. Many of them, for example, pathogens of intestinal infections, remain virulent in water for a long time (weeks or even months). For domestic and drinking purposes, open and underground reservoirs are used as sources of water supply.

Drinking water. In terms of composition and properties, drinking water must be safe in terms of epidemics, harmless in chemical composition and have favorable organoleptic properties. Artesian waters, which usually do not need purification, best meet these requirements. Water from open reservoirs is treated for waterworks to improve physical and chemical properties and release from microorganisms.

Cleaning drinking water is carried out in several stages. The first is the liberation of water from suspended matter by settling in special basins - settling tanks. For more effective clarification and decolorization of water, settling is carried out using coagulants. The main coagulants are aluminum and iron salts. As a result of the reaction of coagulants with carbon dioxide salts contained in water, aluminum or ferric hydroxides (when using iron salts) are formed, which precipitate in the form of flakes. As the flakes settle, they carry suspended matter and microorganisms with them.

After settling, the water is filtered. Quartz sand is often used as a filter material. A biological film containing large number microorganisms. Currently, water filtration in combination with coagulation is being used, using material with adsorption properties for filtration, for example kaolin, bentonite.

After passing through the filters, the water is completely freed from suspended solids and most microorganisms. However, a certain amount of bacteria still remains in it, and pathogenic ones may also remain. Therefore, after filtration, water is disinfected - disinfected, often by chlorination. Usually chlorine gas or other chlorine-containing substances (hypochlorites, bleach, chloramines) are used. Chlorine, even in small concentrations (fractions of mg/l), has a detrimental effect on many microorganisms. Bacterial spores are more stable than vegetative cells. In addition to free chlorine, undissociated molecules of hypochlorous acid (HOC1), formed during the hydrolysis of chlorine in water, have a significant bactericidal effect. Hypochlorite ions (OC1), formed as a result of the dissociation of hypochlorous acid, also have a detrimental effect on microorganisms. Bacteria

Apparently, atomic (active) oxygen, formed during the reaction of chlorine with water, also has cidal properties.

The dose of chlorine required for disinfection should be greater, the higher the concentration of organic substances in the water, since chlorine is spent on their oxidation. If there is a lack of residual (active) chlorine, the water is not disinfected; Excessive amounts of chlorine give water an unpleasant taste and odor.

New methods of water disinfection are being introduced into water supply practice - ozonation and irradiation with bactericidal ultraviolet rays. Ozonation, in addition to its bactericidal effect, improves the organoleptic properties of water. Ultraviolet irradiation can only be used for water with slight color and turbidity. /Assessment of the quality of drinking water is carried out according to a set of chemical, organoleptic and bacteriological indicators.^ in accordance with GOST 2874–82 total number bacteria should not exceed 100 cells per 1 cm3, the number of E. coli (coli index) should be no more than 3 per 1 liter, and the coli titer should not be less than 300 cm3. Water from wells and open reservoirs is recognized as benign if the coli index is no more than 10 (coli titer is at least 100 cm 3), the total number of bacteria should not be higher than 1000 per 1 cm 3.

d. Due to the fact that the water of open reservoirs and the water of ground wells can be significantly contaminated, during its (bacteriological study) the presence of other (except E. coli) sanitary indicator microorganisms is taken into account: enterococci and Clostridium perfringens as indicators of fecal contamination, as well as bacteria of the genus Proteus, the presence of which in water indicates the presence of significant amounts of organic substances in it.

Sanitary standards for water used in the food industry and catering establishments are the same as for drinking water.

Wastewater. This is water used in industrial enterprises for various production processes, contaminated with a variety of organic and mineral impurities. Such contaminated water is called industrial wastewater. At individual industrial enterprises, the amount of wastewater amounts to thousands and tens of thousands of cubic meters per day.

A large amount of polluted water is also obtained as a result of the population’s use of clean water for domestic needs. Such water is called domestic wastewater. The amount of domestic wastewater, depending on the improvement of residential areas, ranges from 125 to 420 liters per person per day.

Wastewater, in addition to a large amount of organic and mineral contaminants, contains a lot of different microorganisms, including pathogenic ones.

The removal of wastewater from the place of its generation is regulated by special rules. Before being discharged into open water bodies, wastewater must be treated. The degree of purification depends on the quantity and chemical composition of the water, as well as on the nature of the reservoir into which it can be discharged.

Wastewater treatment is carried out various methods– physical, chemical and biological (biochemical). After mechanical cleaning– settling – wastewater containing a lot of organic substances is subjected to biological methods cleaning. These purification methods are based on the use of the biochemical activity of aerobic and anaerobic microorganisms - their ability to process organic and mineral substances in the processes of constructive and energy metabolism of the cell. Aerobic biological treatment is carried out in natural and artificial conditions. Under natural conditions, wastewater treatment is carried out by filtering it through layers of soil on special land plots called filtration fields and irrigation fields, as well as in biological (treatment) ponds.

Soil microorganisms oxidize organic matter in seeping water, turning them into inorganic compounds, i.e., by mineralizing them, they purify the water. In addition to being freed from organic contaminants, up to 99% of the bacteria present in the wastewater are retained in the soil. The purified wastewater that passes through the soil enters collecting drainage pipes, through which it is discharged into an open reservoir.

Irrigation fields differ from filtration fields in that the same land plots used simultaneously for wastewater treatment and for growing crops (herbs, vegetables, fruit trees etc.). Irrigation fields purify significantly less wastewater than filtration fields of the same area, but plants use valuable fertilizer substances obtained from the mineralization of organic substances in wastewater.

Biological ponds are artificial reservoirs connected in series into which diluted waste water is discharged. The purification of water in them is similar to the processes occurring in reservoirs during their natural self-purification (see p. 174). Biological wastewater treatment is most widely used in artificial conditions at special treatment facilities - biological filters and aeration tanks. Biological treatment is preceded by mechanical treatment.

Biological filters (biofilters) are tanks filled with coarse material (slag, crushed stone or plastic porous blocks)./Wastewater is filtered through the thickness of this loading material. Air supply (aeration) into biofilters can be natural or artificial (forced), when air is blown through the thickness of the load by fans. These 7 biofilters

called aerofilters. On the surface of the loading material, various organisms (microorganisms, protozoa, etc.) develop abundantly, forming a more or less powerful film called biological.

The process of wastewater purification under the influence of biological film microorganisms consists of two phases. First, carbon-containing organic substances are oxidized and ammonification of nitrogen-containing organic substances occurs. After oxidation of the main mass of organic substances, the resulting ammonia salts are subjected to oxidation, which turn into salts of nitrous and nitric acids (nitrification process). The first phase occurs mainly in the most superficial layers of the loading material, the second - in its deeper layers.

Aerotanks are flow-through pools into which, together with settled waste water introduce a certain amount of so-called activated sludge(in the form of flakes), the bulk of which consists of various microorganisms. The mixture of wastewater and sludge, flowing through the aeration tank, is subject to active aeration. The air entering the aeration tank, a source of oxygen, maintains sludge in suspension and vigorously mixes the liquid, which promotes constant and rapid contact of activated sludge organisms with wastewater nutrients and oxygen. In aeration tanks, the same process occurs as in biofilters—sequential biochemical oxidation of organic substances in waste liquid. However, in aeration tanks the process is much more intense than in biofilters due to better aeration of the waste liquid. The qualitative composition of the micropopulation of biofilm and activated sludge can serve as an indicator of the operation of a wastewater treatment plant.

After passing through the biofilter and aeration tank, the water enters settling tanks to free it from biofilm and activated sludge, and then is discharged into the reservoir. Sometimes water is disinfected with chlorine or bleach before release.

During wastewater treatment, a large amount of sediment accumulates, containing many organic substances and microorganisms, including pathogenic ones. Treatment and neutralization of sediments are carried out in digesters.

Complex organic compounds of sediment (proteins, fats, fiber, etc.) as a result of various processes of fermentation and decay are converted into fatty acids, alcohols and gaseous products (carbon dioxide, ammonia, methane, hydrogen). Among gaseous products, 60–65% is methane, which can be used as a flammable gas. The digested sludge is dewatered, dried and transported to agricultural fields as fertilizer, and in briquetted form it can also be used as fuel.

Pollution and self-purification of water bodies. The aquatic environment and the organisms inhabiting it are closely interconnected. When untreated or undertreated wastewater is released into a body of water, the living conditions of its natural population change dramatically. Many organisms living in unpolluted water die out, and others begin to develop in the reservoir to replace them.

The degree of contamination of a reservoir with organic substances is called saprobity.

At the point of discharge of wastewater that contains organic contaminants, many saprophytic microorganisms develop and the processes of decay and fermentation they cause actively occur in the water. In this highly polluted zone of the reservoir, called the polysaprobic zone, the number of bacteria reaches several million per 1 cm 3 of water.

As the content of organic compounds decreases, i.e., as they become mineralized, the number of saprophytic bacteria also decreases; their number is ΙΟ 5 -–10 4 per 1 cm 3 of water. In this moderately polluted zone of the reservoir, called the mesosaprobic zone, other aquatic organisms (protozoa, rotifers, algae, etc.) begin to develop.

Saprophytic bacteria die off as a result of lack of food, under the influence of antibiotic substances secreted by some algae. Rotifers and protozoa eat bacteria, and they are lysed by a bacteriophage. Normal ecological conditions, fauna and flora are gradually being restored in the reservoir. In this zone of the reservoir, called the oligosaprobic zone, the number of saprophytic bacteria decreases to 10 2 - 10 1 cells per 1 cm 3 of water.

This process of cleansing a reservoir from organic contaminants and bacteria is called natural self-purification. Its intensity depends on the amount of pollutants entering the reservoir, their composition, and the degree of dilution. clean waters, oxygen saturation of water, its temperature.

Although the water of natural reservoirs has a self-purifying ability, if large amounts of organic contaminants enter over extended areas, it is sanitary unsafe and unsuitable for use. In this regard, in our country the release of wastewater into reservoirs without pre-treatment not allowed.

The problem of protection and use of natural water resources in the Soviet Union is given much attention, which is reflected in a number of resolutions of the CPSU Central Committee and the USSR Council of Ministers. For construction treatment facilities large funds are allocated. A number of industrial enterprises carry out recycling and reuse of water in technological processes, which leads to a reduction in wastewater volume. For recent years in our country V Due to the reduction in the discharge of untreated industrial wastewater, the sanitary and hygienic condition of many rivers has improved.

As a habitat, air is unfavorable for the development of microorganisms, since it lacks nutrients: Microorganisms enter the air with dust blown from the surface of the earth by the wind. In the air, microbes either quickly die off or settle again on the surface of the earth and on various subjects. The contamination of air with microorganisms is constantly changing; The cleaner the air, the poorer it is in microorganisms. Above snowy plains, over the ocean and high mountains, the air contains almost no germs. There are more of them in the air over the valleys than over the mountains. In the air above fertile soil, fields and vegetable gardens more than over a desert or snow field.

Air microflora is exposed to a number of adverse effects: drying and exposure to direct sunlight. Depending on the weather, the microflora of the air changes significantly. The air of warm countries contains more microbes than the air of cold countries.

The greatest number of microorganisms is contained in the air in summer, the smallest in winter. The saturation of air with microorganisms also depends on the distance from populated areas: in the lower layers of air and above large cities there are more of them than in the upper layers of air and above small cities settlements.

The composition of air microflora is different. Basically, microorganisms in the air are harmless - these are causative agents of various fermentations, molds and yeasts. However, pathogenic microbes and viruses are also found in the air. In contrast to the pathogenic microflora of soil and water, pathogens of respiratory tract infections predominate in the air. Indoor air often contains staphylococci, streptococci, pathogenic fungi, tuberculosis and diphtheria bacilli, pneumococci, and meningococci.

Air is a source of microbial contamination of food products, technological raw materials and equipment, industrial cultures of microorganisms, etc. Therefore, air purity is an important condition for production high quality at food industry enterprises.

In dusty rooms, the number of microorganisms increases to tens of thousands of cells in 1 m 3 of air. In non-residential basements and cellars the air contains fewer microbes than in open places. Dust is especially contaminated with microbes: 1 g of indoor and street dust contains about 1 million microbes, among which pathogenic ones are often found.

High contamination of air with microorganisms indicates low sanitary condition premises. If there are up to 500 microbial cells in 1 m 3 of residential or production premises the air is considered clean.

Prokaryotes have almost unlimited abilities to spread across our planet. Microorganisms usually inhabit soil, water, air, as well as plant, animal and human organisms. They are often found in the most inappropriate ecological niches. Thus, some types of bacteria (for example, Bacillus submarinus) are able to live in oceans at depths of more than 5000 meters; extremely thermophilic bacteria (Thermus aquaticus) are isolated from the water of hot springs, halophilic bacteria are found in the water of the Dead Sea.

In each microzone, prokaryotes form complex microbiocenoses. The structure and functions of microbiocenoses largely depend on the totality of operating environmental factors. Certain environmental factors can stimulate the development of microorganisms or have a depressing effect on them.

Humidity. The development of microorganisms, like any other organisms, is primarily determined by humidity conditions. It is the presence of moisture that determines the level of metabolism in the cell, the growth energy and reproduction of the bacterium. Different groups of prokaryotes are characterized by very different requirements for humidity and differently react and dry out. Most bacteria develop normally at environmental humidity above 20%. Drying of bacteria leads to dehydration of the cell cytoplasm, almost complete cessation of metabolic processes and ultimately to the transition of the microbial cell to a state of suspended animation

Temperature. Prokaryotes do not have physiological mechanism, regulating the temperature of the cell, and, therefore, their vital activity directly depends on the ambient temperature. Bacteria, like any other organisms, have their own temperature range. It is characterized by three cardinal points: minimum temperature, below which the growth and development of bacteria stops; optimal temperature corresponding to the highest microbial speed; the maximum temperature above which the growth rate of bacteria is reduced to virtually zero.

Based on the temperature range, all prokaryotes are divided into three groups: psychrophiles, mesophylls, thermophiles. Psychrophiles (from the Greek psychros - cold, phyleo - love) are represented by bacteria that develop at low temperatures from -5°C to +35°C; among them, there is a subgroup of obligate psychrophiles, unable to grow at temperatures above +20 C. The second, very extensive a subgroup consists of facultative psychrophiles - bacteria adapted to the action of variable temperatures from -5°C to +35°C.

The mechanism of action of low temperature on a microbial cell is the freezing of metabolic processes in it, the cessation of growth and reproduction, and the transition of the microbe to a state of suspended animation. Mesophiles (from the Greek mejoj - average) include the overwhelming majority of prokaryotes, for which the temperature range lies from +1 ° C to + 47 ° C. This group includes many pathogenic bacteria that cause disease in warm-blooded animals and humans. Thermophiles (from the Greek thermos - heat, heat) constitute a fairly large and diverse group of bacteria growing in the temperature range from +10°C to +90°C. Unlike low temperatures, high temperatures have a more detrimental effect on the microbial cell. When the temperature rises above the maximum limit, RNA is released from the cell, the activity of enzymatic systems is disrupted, proteins are denatured, and ultimately causes irreversible degradation of cellular structures. Particularly resistant to high temperatures exhibit bacterial spores that can withstand boiling temperatures for 2-3 hours.

Light. Light acts as a disinfectant on bacteria. Direct sunlight kills most germs within a few hours. Pathogenic bacteria are more sensitive to light than saprophytes. The hygienic effect of light, as a natural disinfectant, is very great; it frees the external environment from pathogenic bacteria. The most powerful bactericidal effect is exerted by rays with a short long wavelength - ultraviolet. The source of these rays are mercury-quartz lamps and bactericidal uviol lamps. Other types of radiant energy - x-rays and gamma rays - cause the death of microbes only when exposed in large doses. Bacteria are protected from sunlight by pigments - carotenoids, which are found in many bacterial cells.

Pressure. Microorganisms are little sensitive to atmospheric pressure, which is apparently due to the low sensitivity of proteins to its denaturing influence. Only pressure of 10,000 atmospheres has a sharply negative effect?

Chemicals. Chemical toxic substances, entering the bacterial cell, interact with one or another of its important components and disrupt the functions of the bacterium. This leads to the growth of the organism stopping (bacteriostatic effect) or its death (bactericidal effect)

Qualitative composition of air microflora

Air is an environment containing a significant number of microorganisms. They are transported by air over considerable distances. In one cubic meter air and the number of sanitary indicator bacteria. To determine sanitary indicative microorganisms, sedimentation and aspiration methods are used, but inoculations are carried out on selective nutrient media.

The body cavities of humans and animals communicating with the outside world are populated by an abundant normal microflora that is fairly constant in qualitative composition and changes relatively little during infectious diseases. For many types of microbes (inhabitants of the body of a healthy person), the oral cavity or intestines are the only natural environment habitat. Therefore, the detection of such microbes outside the body indicates contamination of the object with corresponding secretions. Finding representatives of the oral microflora in the studied material, we have the right to think about the ingress of mucus from the respiratory tract, which may contain pathogens of diphtheria, scarlet fever, tuberculosis and others. By detecting normal intestinal inhabitants, we conclude that there is fecal contamination and the possibility of the presence of typhoid or dysentery bacilli. The microbes isolated in these cases serve as indicators of sanitary problems and the potential danger of the objects under study, and therefore are called sanitary indicators.

The qualitative composition of air microflora is not stable and largely depends on local sources of pollution. Usually, when analyzing air microflora, pigmented saprophytic bacteria of the genus Micrococcus, spore forms of the genus Bacillus, as well as actinomycetes, molds and yeasts are isolated in large quantities.

Spore bacteria. These are gram-positive rod-shaped bacteria with peritrichally arranged flagella. They are divided into two large genera: aerobic, which belong to the genus Bacillus, and anaerobic, which belong to the genus Clostridium. Bacillus spores can be located in various parts mother cell. In this case, its shape either takes the form of a mace, a spindle or a drumstick. Anaerobic bacteria are widely distributed in soils, water bodies and other substrates. They take part in the decomposition of various organic substances and are pathogens of diseases in humans, animals and plants.

Pigment-forming coccoid microorganisms. This group represents bacteria of the Mikrococcus and Streptococcus families. This broad group of microorganisms includes both saprophytes that live in the external environment and in the body of humans and animals, as well as pathogenic species that cause various purulent diseases. The Micrococcus family includes cocci measuring 0.5 - 3.5 µm, dividing in more than one plane and forming irregular clusters. Staphylococci are representatives of normal microflora. Their main location is the mucous membranes of the upper respiratory tract of humans and some warm-blooded animals, as well as the skin. Staphylococci are also present in the intestines healthy people. Staphylococci get into the environment, into the air, onto household items with saliva and sputum when talking, coughing, as well as from the skin, from places of inflammation and wound surfaces. Staphylococci belong to the Micrococcus family, the most studied are three species: St. Aureus St. epidermidis, St. saprodiccus. Staphylococci have a spherical shape, are arranged in the form of bunches of grapes, are gram-positive, do not form spores or capsules, and are immobile. They are unpretentious to nutrient media, are facultative anaerobes, and on meat peptone agar they form round, opaque colonies with a diameter of 1 - 2 millimeters, smooth, shiny, with different pigments. Staphylococci are recommended as sanitary indicator microorganisms for indoor air. Since staphylococci comprise not only saprophytic groups of microbes, but also pathogenic ones with a vaguely expressed degree of their pathogenicity and virulence. Staphylococci are the causative agents of pustules, skin diseases, boils, abscesses, and phlegmons. In a weakened body, the penetration of staphylococci into the blood is accompanied by the formation of sepsis with the formation of secondary abscesses in internal organs: liver, lungs, kidneys. Most common in women giving birth. Some staphylococci, getting into food products and multiplying in them, cause poisoning.

Streptococci, like staphylococci, are inhabitants of the upper respiratory tract of humans and many animals. They are constantly and in large quantities present in the oral cavity, nose and nasopharynx of patients with chronic streptococcal infections of the upper respiratory tract, as well as healthy people, and therefore can enter the indoor air with saliva and sputum when talking and coughing. The main difficulty in using streptococci as sanitary indicator microorganisms is that streptococci represent a large group that includes a large number of species: from saprophytes to pathogenic streptococci that cause diseases such as scarlet fever, sepsis and many purulent-inflammatory processes. Streptococci belong to the Streptococcus family. View St. pyogenes has highest value in human pathology. Morphologically, they are chains of round or slightly oval cocci with a diameter of 0.6-1 µm grams - positive. They do not form spores and are immobile; some pathogenic strains form a capsule. On solid nutrient media, colonies of streptococci are gray, opaque, small, 1 mm in diameter. Streptococci are not very resistant to environment, they can only be preserved for several days in the dust of rooms: on linen, household items of the patient. Streptococci are not found in the air of premises uninhabited by humans.

Actinomycetes. They are a group of Gram-positive organisms capable of mycelial growth and hyphal formation. The mycelium of actinomycetes is unicellular, with a diameter of about 1.5 microns; substrate and aerial mycelium are distinguished. On the latter, spore bearers are formed, from which conidia, which serve for reproduction, are released. All actinomycetes have a cell structure typical of prokaryotes. These are predominantly aerobic organisms. Many actinomycetes secrete antibiotic substances that are used to fight infectious diseases. Among human and animal diseases.

Mold fungi. Molds belong to perfect fungi, which are characterized by the presence of a sexual method of reproduction. The most common are representatives of the genera Misor, Penicillum, Aspergillus. The fruiting body of these mushrooms most often has the shape of a head, inside which many endospores are enclosed. Currently, molds have attracted attention due to the fact that some of them secrete active antimicrobial substances - antibiotics. The diameter of their hyphae ranges from 5 to 50 microns. The cell wall of most molds contains chitin or compounds close to it. As pathogens of human diseases, molds are of little importance. Yeast mushrooms. Yeast cells are round, oval or rod-shaped, with a diameter of 4-12 microns. On solid nutrient media, yeast grows in the form of convex, round, lobed, smooth and folded colonies of a paste-like consistency. Yeast colonies are usually either colorless or yellowish-orange or pink. Thus, among the microbes inhabiting the air there are saprophytes, but there are pathogenic microorganisms that cause various human diseases. Therefore, the study of air microflora and assessment of the bacteriological danger of air is an urgent task, which is dealt with by sanitary microbiology.

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Introduction

The air environment is unsuitable for the proliferation of microbes due to the lack of nutrients, the presence of sunlight that is harmful to many bacteria, etc. Therefore, air pollution by microorganisms is usually relatively low. However, the air in urban areas and crowded places, especially industrial centers, is characterized by increased dust content. It is the dust particle that, as a rule, is a favorable environment for the life of microorganisms and their colonies. Up to 383 species of bacteria and 28 genera of microscopic fungi are found in the atmospheric air, which is due to the variety of sources of air pollution, which are humans, wild and domestic animals, plant organisms, and soil cover. Not all microorganisms are pathogenic.

The school is one of the places with large crowds of people. Throughout the day, a large number of dust particles accumulate within the school, which serves as a favorable environment for the reproduction of organisms. During lessons, we inhale these particles, and, consequently, microorganisms too. We became interested in where in our school there is the largest concentration of microorganisms, so studying this topic is for us relevant.

Before starting the study, we put forward hypothesis: the greatest number of microorganisms will be observed in places where there is a large concentration of students: classrooms, locker rooms and toilets.

Purpose of the work: detect microorganisms in the air.

To achieve this goal, we have identified the following tasks:

get acquainted with the literature on this topic;

find out which areas of the school premises are the most frequently visited and, therefore, the most dusty;

detect the presence of microorganisms in the air different rooms schools.

Object of study: air from different rooms of school No. 30.

Subject of research: the presence of microorganisms contained in the air within the school.

When writing the work we used the following methods:

Reading literature;

Observation;

Experiment.

Chapter 1. Theoretical part.

Literature review.

Microbiological analysis of air was started in the middle of the last century by the great French scientist Louis Pasteur, who in his experiments proved the presence of microorganisms in the air. Human contact with microorganisms in the air is observed throughout life, and there are reasons for increased attention enough for this question. Numerous bacteriological analyzes of the air have established the presence of microorganisms both in atmospheric air and in the air of enclosed spaces. The microflora of the discovered organisms is very diverse, and the air is their natural distribution route. Considering this fact, we are exposed to the influence of microorganisms on the street, at home and in the workplace, and the relationship between air cleanliness and public health is obvious. Microbiological analysis of air is carried out in order to study the conditions of the air environment and develop a set of hygienic measures that are aimed at creating optimal conditions for the prevention of airborne infections.

Most microbes belong to the group of bacteria. This group is widespread in nature and the most well studied, so the study of microbes usually begins with bacteria.

Bacteria are divided according to the shape of their cells: into spherical - cocci, rod-shaped or cylindrical - the bacteria themselves - and convoluted - vibrios and spirilla. In addition, there are also filamentous bacteria and myxobacteria.

Rod-shaped bacteria make up the largest groups. This group includes many pathogens of infectious diseases: anthrax, brucellosis, tetanus, and intestinal infections.

But among the bacteria of this group there are also many useful microbes, for example intrifiers, and bacteria that absorb nitrogen from the air.

Coiled bacteria are called spirilla if they have the appearance of a spiral with several curls, and vibrios if they have one curl not exceeding ¼ turn of the spiral. Typical representatives of vibrios are the causative agent of cholera and aquatic vibrios, very similar to Vibrio cholerae, but not pathogenic, common inhabitants of fresh water bodies, as well as spirilla.

Filamentous bacteria are long threads of cells joined together. These are mainly aquatic microorganisms.

Myxobacteria (mucous bacteria) are the most highly organized bacteria. Most species have a well-formed core.

The internal structure of bacteria remains insufficiently studied due to technical difficulties in the research methodology.

Air microflora can be divided into constant, frequently occurring, and variable, representatives of which, entering the air from their natural habitats, do not remain viable for long. Pigment-forming cocci, rods, yeasts, fungi, actinomycetes, spore-bearing bacilli and clostridia, etc., i.e., microorganisms resistant to light and drying, are constantly found in the air. There are more microorganisms in the air of large cities than in rural areas.

The composition of microflora and the number of microorganisms found in 1 m 3 of air (microbial number of air) depend on the sanitary and hygienic regime, the number of people in the room, their health status and other conditions. Pathogenic microorganisms can also enter the air from animals and people (patients and carriers).

Dust particles serve as a favorable environment for the life of various microorganisms. Scientists have discovered 383 species of bacteria and 28 genera of microscopic fungi in the air. Sources of air pollution are soil, water, plants, animals, humans and waste products of living organisms.

The microflora of the air depends on the microflora of the soil or water above which the layers of air are located. Microbes can multiply in soil and water, but they do not multiply in the air, but only persist for a while. Raised into the air by dust, they either settle with droplets back to the surface of the earth, or die in the air from lack of nutrition and from the action of ultraviolet rays. Therefore, the microflora of the air is less abundant than the microflora of water and soil

The air in enclosed spaces is very rich in microbes, especially in cinemas, train stations, schools, livestock premises and others. Along with harmless saprophytes, pathogenic microbes may also be present in the air, especially indoors: tuberculosis bacillus, streptococci, staphylococci, influenza pathogens, whooping cough, and so on. Influenza, measles, and whooping cough are transmitted exclusively through airborne droplets. When you cough or sneeze, tiny aerosol droplets containing pathogens are released into the air, which other people inhale and, when infected, become ill. Microbiological analysis of air for pathogenic flora is carried out only for epidemic indications. The cleaner the air in public places, around human habitation and in rooms, the fewer people are sick.

Microbes harm not only human health. Pathogens of animal and plant diseases also spread through the air. Microorganisms, together with dust, settle on food products, causing them to sour and putrefactive decomposition

Microbiological analysis of air has been carried out for a very long time. Research has proven that indoor air is very rich in microorganisms. Dust particles located in enclosed spaces serve as a favorable environment for the life of various microorganisms. The composition of microflora and the number of microorganisms found in 1 m 3 of air (microbial number of air) depend on the sanitary and hygienic regime, the number of people in the room, their state of health and other conditions.

Chapter 2. Practical part

Preparation of nutrient medium

Microbes tend to multiply when they enter a nutrient medium, and from one microorganism, under certain conditions, one colony grows, which can contain many thousands of microbes. Such a colony is clearly visible to the naked eye. The process of growing a colony of microorganisms is called incubation.

We prepared the nutrient medium for sowing microorganisms as follows: In a flask with a volume of 750-1000 ml, brew 2 tbsp. spoons of water-soluble starch in 1 glass of water. The resulting solution was heated to boiling in a sealed container and boiled for 10 minutes, avoiding strong boiling. The resulting thick gel was poured into Petri dishes (previously sterilized in a medical office under quartz lamp- Appendix 1), closed with a lid and cooled.

We inoculated microorganisms from the air as follows:

Numbered Petri dishes

Cup No. 1 was left as a control (it was not opened throughout the entire period of sowing and incubation)

Cup No. 2 - 11 was opened and left open for 5 minutes in the study rooms, after which they were closed with lids.

The number and growth of colonies of microorganisms in Petri dishes were monitored during 3-7 days of incubation. Observations were recorded in table No. 1

The number of colonies grown on the nutrient medium in each Petri dish was counted and described. ( The experiment can be considered completed correctly if no more than 3 colonies grew in dish No. 1 (control) after 7 days of observation)

Table No. 1. Offices within which the study was conducted.

Petri dish no.	Cabinet name (No.)
	Control
	Cabinet primary classes
	Gym
	Wardrobe (high school)
	Wardrobe (junior grades)
	Girls toilet
	Corridor (hall 3 floors)

	Geography room (318)
	Computer Science Room
	Library

The description of microbial colonies grown on a nutrient medium was carried out according to the following indicators: shape (round, irregular); surface (smooth, shiny, rough, dry, folded); edge (smooth, wavy, bearded); color; size (diameter).

Over the course of 14 days, we observed the growth of colonies. On day 14 we got the following results (table No. 2), figure No. 1.

table 2.

Description of the colonies

Cabinet name	Description of the colonies
Control cup	The control Petri dish remained closed for 14 days. We did not find a single colony in it; the contents of the cup did not change. The color, composition and shape of the nutrient medium remained unchanged.
Primary classroom	The nutrient medium in the Petri dishes has remained virtually unchanged; in some places, white inclusions of a smooth shape are observed in the amount of 3 pieces.
Gym	One colony is clearly visible on the nutrient medium lilac color, with an area of approximately 2 sq.cm. A light colony begins to form along the edges brown. Colonies have a smooth round shape with smooth edges.
Wardrobe (high school)	The nutrient medium clearly shows two lightly grown colonies. yellow small sizes. The edges of the colonies are wavy, the surface is smooth.
Wardrobe (junior grades)	The nutrient medium clearly shows a large number of dark brown colonies, small size. Colonies by appearance reminiscent of ground black pepper. Some of the colonies settled on the edges of the Petri dish.
Girls toilet	On the nutrient medium, 29 light beige colonies are clearly visible. The main part of the colonies is located in the central part of the Petri dish.
Corridor (hall 3 floors)	Almost nothing has changed on the Petri dish. The peculiarity is that the nutrient medium turned out to be very dried out, nothing sprouted on it.
Technology room (for girls)	92 colonies are clearly visible on the nutrient medium white. A special feature is that the colonies are arranged in a circle, in concentrated rings.
Geography room (No. 318)	On the nutrient medium, 4 colonies are clearly visible orange color, almost completely covering the Petri dish. A special feature is that the nutrient medium has become more liquid.
Computer Science Room	Violet, white and light colonies are clearly visible on the nutrient medium. beige color. The peculiarity is that the white colony has porous structure.
Library	On the nutrient medium, 92 colonies are clearly visible, white in color, with small sizes. The colonies are located close to each other, resembling inclusions. A light brown colony begins to appear on top of the pinpoint colonies.

Figure 1. Number of colonies growing in offices.

The main part of the colonies had a smooth shape and smooth edges. In the computer science classroom, one colony had a porous structure, and in the junior school wardrobe, the colonies were represented by dots (Appendix 1)

As can be seen from the figure, a larger number of colonies grew in the following classrooms: wardrobe (junior grades), technology classroom (for girls) and in the library. The main reason is that a large number of students are present in these classrooms throughout the day, and students in the lower grades are in the cloakroom for two shifts.

No colonies grew at all in the control plate. The reason is that it did not open after sterilization throughout the entire sowing. Also, there were no colonies in the dish, which was inoculated in the corridor. We assume this happened because the sowing was carried out immediately after washing the floors and wet cleaning was carried out in the corridor several times throughout the day.

As can be seen from the table, the grown colonies had different colors, sizes, shapes and edges. Detailed description We want to do them and determine the species composition in the future using a digital microscope.

Using a nutrient medium, you can grow colonies of microorganisms within the school. The grown colonies differ from each other in number, shape, size, and the nature of the edges.

Conclusion.

As a result of the study, we came to the following conclusions:

The air of an enclosed space is very rich in a variety of microorganisms that can be detected during sowing on a nutrient medium;

The absence of colonies in the control Petri dish indicates that the inoculation was carried out correctly.

The maximum number of colonies of microorganisms is typical for offices where maximum quantity students: wardrobe, library, technology room.

Wet cleaning and ventilation significantly reduces the number of microorganisms in the air, as evidenced by the absence of colonies in the corridors.

Based on the data obtained, we can say that our hypothesis was completely confirmed.

Further direction of work:

Do a seeding in the remaining rooms;

Determine the species diversity of grown colonies using a digital microscope;

To convey to school students information about the importance of ventilation and wet cleaning to improve indoor air quality.

5. Literature.

1. Anikeev V.V., Lukomskaya K.A. Guide to practical classes in microbiology. - M.: “Prosveshcheniye”, 1983.

2. Gusev M.V., Mineeva L.A. Microbiology. Third edition. - M.: Rybari, 2004

3. Muravyov A.G., Pugal N.A., Lavrova V.N. Ecological workshop: Tutorial with a set of instruction cards / Ed. Ph.D. A.G. Muravyova. - 2nd ed., rev. - St. Petersburg: Christmas+, 2012. - 176 p.: ill.

Internet resources:

4.http://www.ebio.ru/gri06.html

5.http://www.webmedinfo.ru/library/mikrobiologija.php

Applications

appendix 1.

Sterilization of Petri dishes in a medical office

appendix 2.

Grown colonies

Control cup

Primary classroom

Gym

Wardrobe (high school)

Wardrobe (junior grades)

Girls toilet

Corridor (hall 3 floors)

technology room (girls)

Geography office

Computer Science Room

At the slightest breath of wind, a mass of small dust particles rises into the air, and with them microbes. The ocean of air is a barren desert for microorganisms: they have nothing to eat there. In addition, the sun's rays are fatal to many microbes. Usually the presence of microbes in the air is short-lived. On the smallest specks of dust, like parachutes, they settle to the ground. For some bacteria and fungi, air currents are the main route of spread. Mold spores are often carried through the air over very long distances.

The higher and further from the ground, the fewer microbes. There are not as many of them in the mountain air as in the air of narrow and dusty streets. There are very few microbes above the sea, away from the shores. Participants on Arctic and Antarctic expeditions sometimes have to work knee-deep in icy water, but usually none of them contract contagious diseases associated with colds. This is explained by the fact that the air in the polar zone is almost free of microorganisms, including pathogens.

Scientists have found that above Moscow at an altitude of 500 m, 1 m 3 of air contains about 3 thousand microbes, at an altitude of 1000 m - already 1700, and at an altitude of 2 thousand m - only 700-800 microbes. In a strong wind, when dust spreads over the city like a gray haze, the number of microbes at an altitude of 500 m increases to 8 thousand. Microbes were also found at an altitude of 6 km. Even at an altitude of 23 km, where the atmosphere is permeated with cosmic rays, bacteria and molds were caught using balloons.

Millions of microorganisms are carried along with dust in the air of industrial cities. A liter of air in a poorly ventilated living room contains about 500 thousand dust particles. A person inhales about 10 thousand liters of air per day. We absorb most microbes without any ill effects. But pathogens of infectious diseases can also appear in the air, especially in enclosed spaces.

Some microbes (causative agents of plague, whooping cough) quickly die in the air. But the tuberculosis bacillus and microbes that cause suppuration endure drying for a long time. Tuberculosis bacilli remain viable in dust for up to 3 months. Together with dust particles, they are carried through the air over long distances.

Infection can spread not only with dust. When a patient sneezes or coughs, pathogens enter the air along with droplets of moisture. In each droplet of cough splashes from tuberculosis patients, up to 40 thousand tuberculosis bacilli were found. With the smallest splashes of sputum, microbes fly away 2-3 m when coughing, and up to 9 m with a strong cough.

The cleaner the air in public places, around human habitation and in rooms, the less people get sick. It is estimated that if you sweep the vacuum cleaner brush over the surface of an object four times, up to 50% of germs are removed, and if you sweep it twelve times, almost 100%. Forests and parks are of great importance in the fight for clean air. Green spaces settle, absorb dust and release phytoncides that kill microbes.