At the 111th American Society for Microbiology (ASM) meeting in New Orleans this week, Alexander Michaud of State University Montana at Bozeman presented his team's latest findings in the new emerging field of "bioprecipitation," in which scientists are investigating the extent to which bacteria and other microorganisms influence weather events.

In a keynote on Tuesday, Michaud talked about how he and his team found a high concentration of bacteria in the center of the hailstones. The center of the hailstone is the first part of the discovery, the "embryo":

Michaud said that water molecules need a "core" around which they will accumulate and this will lead to precipitation in the form of rain, snow and hail.

« There is growing evidence that these nuclei may be bacteria or other biological particles." added Michaud.

He and his team examined hailstones more than 5 cm in diameter that fell on the campus of the university during a hailstorm in June 2010.

They analyzed meltwater from four layers in each hailstone and found that the inner core contained the most live bacteria, as evidenced by their ability to grow.

The term "bioprecipitation" was first coined in the early 1980s by David Sands, a professor and plant pathologist at Montana State University. This is currently an emerging area where scientists are investigating how ice clouds form and how bacteria and other microorganisms contribute to this by forming nuclei, particles around which ice crystals can form.

As soon as the temperature in the clouds becomes more than -40 degrees Celsius, ice does not spontaneously form:

« Aerosols in clouds play a key role in the processes leading to precipitation».

Christner explained that while different types of particles can serve as nuclei for ice formation, the most active and natural of them is biological, capable of catalyzing the formation of ice at around -2 degrees Celsius.

The most well studied is Pseudomonas syringae, which can be seen as spots on tomatoes after frost.

“Strains of P. syringae have a gene that codes for a protein in their outer membrane that binds water molecules into an ordered arrangement, providing an efficient template that enhances ice crystal formation. Christner explained.

Using a computer model to simulate conditions in aerosol clouds, the researchers found that a high concentration of biological nuclei can influence many events in the Earth's atmosphere, such as the size and concentration of ice crystals in clouds, cloudiness, the amount of rain, snow, hail that falls on ground, and even helps insulate against solar radiation.

Given the volume of nuclei in the atmosphere and the temperature at which they function, Christner concluded that "biological nuclei may play a role in the Earth's hydrological cycle and radiation balance."

Although the atmosphere is hostile environment for the development of microorganisms, the latter are constantly in it. The conditions that exist in the atmosphere do not completely exclude the possibility of microorganisms living in it, especially in the lower layers - the troposphere. It constantly contains water vapor, gaseous nitrogen and carbon and other elements. Microorganisms enter the atmosphere along with dust. They are there for some time in suspension, and then partially settle to the ground, while some die from direct sunlight and drying. In dry sunny weather, microbes die in masses. Due to this, the air microflora is not numerous. It depends on the microflora and the state of the soil, over which the studied air layer is located. There are many more microbes over cultivated soil rich in organic matter than over the soil of barren deserts or over snow-covered fields.

According to the qualitative composition, various pigment forms predominate among the air microflora, giving colored colonies on dense media. This is due to the fact that colorless microbes are more sensitive to the bactericidal action of sunlight, while in pigmented forms, carotenoids serve as protection against the harmful effects of ultraviolet radiation.
The most common inhabitants of the air are yeast, fungi, sardines, staphylococci and various spore bacilli. There are few non-spore-bearing rod-shaped bacteria in the air, as they have a low resistance to drying. Pathogenic microbes can also be found in the air of residential premises, and especially in the environment of patients.
The number of microorganisms and their composition in the air vary depending on many conditions. The dryness of the soil, its dispersion and winds sharply increase the degree of air pollution with microbes. Precipitation significantly purifies the air. The least microbes are in the air over forests, seas and snows. According to the research of B. L. Isachenko, the air above the places covered with all year round snow, can be considered absolutely clean. Under such conditions, 1-2 microbes settle on a bacterial dish per hour.
The workers of the polar expedition of O. Yu. Schmidt in 1930 established the exceptional purity of the air in the Far North. Thus, the air of Novaya Zemlya is almost free from microorganisms. Most microorganisms occur in the layers of air located above industrial cities, over which there is a lot of dust, but as they rise upwards, their number decreases.
The content of microbes in the air also depends on the season. They are least in winter and most in summer, since in winter the soil is covered with snow and the air does not directly come into contact with it. In summer, the wind raises dust from the ground, and with it a lot of microbes. The population of air in spring and autumn occupies a middle position between summer and winter population, since at this time it often rains and the wind raises less dust from moist soil.
Indoor air in winter, on the contrary, is richer in microorganisms than in summer. This is due to the fact that in winter a person spends most of the time indoors. The number of microorganisms is especially high in crowded public spaces - in cinemas, schools, where the air is heated, enriched with moisture, polluted with dust and an admixture of gaseous and vaporous products. The smallest drops of liquid can adsorb various organic substances that enter the air, and thus allow the microorganisms in the drops to multiply. So the air environment provides not only temporary residence of microorganisms there, but sometimes even favors their development.
Microorganisms contained in the air can cause various infectious diseases - influenza, tonsillitis, measles, scarlet fever, etc.
The microbiological study of atmospheric air, as well as indoor air, occupies an important place in the implementation of its purification from bacterial pollution as a measure to combat aerogenic infections.
At present, much attention is paid to the study of atmospheric microbiology in connection with space exploration.

§ The Earth's atmosphere is an illuminated, dynamic, well-mixed environment with a short stay in it 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

The composition of gases in the air Methane (CH 4) - is formed by methanogens, destroyed by methylotrophs. Nitrous oxide and nitric oxide, nitrogen (NO 2, NO, N) - is formed by nitrifiers, destroyed by denitrifiers. Carbon monoxide (CO 2) - formed during respiration, oxidation of organic compounds, fires, and is used in photosynthesis and chemosynthesis Sulfur dioxide (SO 2) - 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 release of the climate system from equilibrium.

Microorganisms in the air are in three main phases of bacterial aerosol Drop, or large-nuclear phase (consists of bacterial cells surrounded by a water-salt shell. The particle diameter is about 0.1 mm or more). Small-nuclear phase (it is formed when particles of the first phase dry and consists of bacterial cells that have retained only chemically bound water on their surface and free water inside the cells, the diameter of most particles does not exceed 0.05 mm). The phase of "bacterial dust" (From the first two phases, bacteria can pass into the composition of larger particles that settle in the form of dust on various subjects. Particle size varies from 0.01 to 1mm)

Sanitary and microbiological study of air Sedimentation method Based on the sedimentation of bacterial particles and drops for 515 minutes under the influence of gravity on the surface of the agar of open Petri dishes A x 100 X \u003d ---- 75 cm 2 Aspiration method Based on the forced sedimentation of microorganisms on the surface of a dense nutrient medium or in the trapping liquid. Use the Krotov apparatus

Criteria for assessing indoor air 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: gases (phenol, C 5 H 6 O 3); aerosol (formalin with creolin); UFL; air removal (ventilation); using air ionizers.

The quantitative and qualitative composition of the microflora of 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 over the taiga, sea 1-10 Air in cities 4000-9800 Park air 175-345 Air in rooms for animals 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 (bogs)

Factors affecting the vital activity of microorganisms Temperature Salt composition of water Dissolved gases Acidity of water Redox potential Bottom sediments

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

Sanitary and microbiological examination of water Determination of bacteria of the family Enterobacteriaceae Membrane filter method. The required volume of water - 300 ml - is filtered through 100 ml membrane filters. The filters are transferred to Endo's medium in a Petri dish and incubated at 37 ° C for 24 hours. The number of red and red with a metallic sheen of colonies is counted. Identification of bacteria is carried out according to 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 - in 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 cultures 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 spores of sulfite-reducing clostridia in 20 ml of water. direct seeding method. Inoculate 20 ml of water into tubes with iron sulfite agar (2 volumes of 10 ml in 2 tubes or 4 volumes of 5 ml in 4 tubes), incubate at 44 ° C for 24 hours and count 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 is poured into all cups with the addition of a daily culture of E. coli. Mix, leave to solidify and incubate at 37 ° C for 24 hours. Take into account the result by counting the plaques in Petri dishes in PFU (plaque-forming units) in 100 ml of water. There should be no plaques in the control dish. Titration method. The method is based on the preliminary cultivation of coliphages in the enrichment medium in the presence of E. coli and the 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 Not 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

At the slightest breath of wind, a mass of small dust particles rises into the air, and with them microbes. The air ocean for microorganisms is a barren desert: they have nothing to eat there. In addition, for many microbes, the rays of the sun are deadly. Usually the stay of microbes in the air is short-lived. On the smallest specks of dust, as if on 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 farther from the ground, the less microbes. There are not so many of them in the mountain air as in the air of narrow and dusty streets. There are very few microbes over the sea, away from the coast. Members of the Arctic and Antarctic expeditions sometimes have to work knee-deep in icy water, but usually none of them get sick with contagious diseases associated with colds. This is explained by the fact that the air in the polar zone is almost free from microorganisms, including pathogens.

Scientists have found that over 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. With a strong wind, when dust spreads over the city in a gray haze, the number of microbes at a height of 500 m increases to 8 thousand. Microbes were also found at a height of 6 km. Even at an altitude of 23 km, where the atmosphere is permeated with cosmic rays, bacteria and molds were caught with the help of balloons.

In the air of industrial cities, millions of microorganisms rush along with dust. A liter of air in a poorly ventilated room contains about 500,000 dust particles. During the day, a person inhales about 10 thousand liters of air. Most microbes we ingest without any ill effects. But in the air, especially indoors, pathogens of infectious diseases can also appear.

Some microbes (causative agents of plague, whooping cough) in the air quickly die. But the tubercle bacillus and the microbes that cause suppuration endure drying for a long time. Tuberculosis bacilli remain viable in the 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 the patient sneezes or coughs, pathogens enter the air along with droplets of moisture. Up to 40,000 tubercle bacilli were found in each drop of spray from the cough of tuberculosis patients. With the smallest splashes of sputum, microbes fly off when coughing at 2-3 m, and with a strong cough, up to 9 m.

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

Microbes are not only harmful to human health. The pathogens of animals and plants also spread through the air. Microorganisms, together with dust, settle on food products, cause their sourness, putrefactive decomposition.

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 a habitat are the most favorable, then viruses and bacteria in the air do not live very long.

How bacteria get into the air

If bacteria live in soil and water, then they are present in the air space. This environment is not able to ensure the normal life of microorganisms, as it does not contain nutrients, and UV radiation from the Sun often leads to the death of bacteria.

The movement of air from the surface raises dust and microscopic particles of matter, along with the microorganisms contained on them - this is how bacteria find themselves in the air. They are moved by air currents and eventually settle to the ground.

Since microbes rise from the surface, the bacterial contamination of the air space, 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 less microorganisms it contains. But they are. Bacteria in airspace have even been found in the stratosphere, at an altitude of more than 23 km from the surface, where the air layer is extremely rarefied, and the impact of cosmic rays is very harsh and is not restrained by the atmosphere.

A bacterial sample at a height 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 over a water surface far from the coast.

What bacteria can be in the air

Since bacteria do not live in airspace, but are only carried by wind currents, it is not necessary to talk about some typical representatives of bacteria.

In the air may be the most different kinds bacteria that react differently to being in such an unfavorable environment:

• do not withstand dehydration and quickly die;
• they enter the spore phase and wait months for critical conditions for life.

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

• plague bacillus (causative agent of bubonic and septic plague, plague pneumonia);
• bacterium Borde-Jangu (the causative agent of whooping cough);
• Koch's stick (the causative agent of tuberculosis);
• cholera vibrio (causative agent of cholera).

Almost all of these bacteria, getting into the air, die quite quickly, however, 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 pathogens in the air increases the risk of infection of an individual, as well as the emergence of an epidemic when a significant group of people is exposed to infection.

Bacteria can be transmitted not only with dry particles downwind

When the patient coughs or sneezes, droplets of sputum secreted by him, containing a large number of bacteria that cause the disease, enter the air. Upon contact with a healthy person, droplets of sputum containing pathogenic bacteria, with highly likely will 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.

The difference in the bacterial composition of the air

Naturally, the air in different places has its own characteristics, depending on many factors. If this is a closed area, then great importance The following factors influence the level of contamination of space with bacteria:

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

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

As an assessment of the level of quantity and composition of bacteria, sanitary and hygienic standards applicable to any enclosed space are used:

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

For indoor air, green streptococci and staphylococci are considered to be sanitary indicative 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 outdoors and indoors (apartments, working areas, etc.) is not a static value, but varies depending on the season, 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 studied.

Methods for cleaning the air from microbes

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, domestic or industrial dust, pet hair, tobacco smoke, volatile chemical compounds(furniture, flooring, household chemicals, etc.) and much more.

Various methods can be used to clean the air from bacteria, but first of all, it is necessary 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; at the slightest movement of air, it moves from place to place, and with it the bacteria.

The most reliable way to get rid of dust and bacteria contained in it 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 modern washing vacuum cleaner with HEPA filters can achieve a higher level of cleanliness.

Carpets lying in apartments should be taken out into the street and knocked out - this is a long-known way to get rid of accumulated dust.

Ventilation for air purification

An effective method of cleaning the air from dust and bacteria in both apartments and 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 going to bed).

Air cleaners

These devices are designed to purify the air in residential premises and work areas from impurities that pollute the air. The filtration method is applied when the dust contained in the air, harmful substances and bacteria remain on the filter.

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

Air cleaner 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 - modern high-performance filters; retain all impurities, including bacteria and their spores; as an additional plus - humidify the air in the room.

Humidifiers

In addition to cleanliness, the air must have a certain level of humidity - with dry air in living quarters and work areas, moisture from the skin will saturate the air. What is natural hello to the 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 humidity in the room is the range of 35-50%:

• for a person - the most comfortable humidity;
• for bacteria - a zone of inhibition of development.

Humidifiers are used to maintain an optimal level of humidity in work areas and places of residence.

Depending on the type of humidifiers are:

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

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

A brief overview of the characteristics of humidifiers

1.Ultrasonic humidifiers.

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

Cons: use of distillate; no automatic topping up of water; the threat of development of microflora 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, cleans the room air, tap water is used.

Cons: it works noisily, requires regular cleaning and disinfection, the risk of development of pathogenic microflora and its entry into the air of the room, high wear.

3. Direct spray humidifiers.

High-class equipment, practically devoid of flaws. Of the minuses can be noted high cost and the need for professional installation.

4. Humidifiers - steam generators.

Pros: average cost, disinfection of water by boiling.

Cons: very energy intensive, large size, noisy in operation, require frequent maintenance, direct steam release is a potential hazard.

Humidifiers of any type solve the problem of cleaning the air from dust and bacteria in the work area or living space, you only 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 private use, the less it contains various bacteria, including pathogens.

The importance of green spaces in air purification cannot be overestimated - plants precipitate dust, and the phytoncides released by them kill microbes.

Plants in the apartment

Indoor plants in residential and working areas act as 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;
• scarlet;
• 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 are constantly cleaning the air space from mechanical impurities and toxins, as well as from pathogens. Plants emit volatile phytoncides that kill bacteria.

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