Methods for purifying air from bacteria. Bacteria in the atmosphere play a key role in the formation of precipitation. At what temperature do microorganisms die?
Taking prevailing winds into account, David J. Smith estimated that air samples collected from the summit of a dormant volcano in Oregon would contain large amounts of DNA from dead microorganisms from Asia and the Pacific. He didn't expect anything to be able to survive the harsh temperatures of the upper atmosphere and reach the research station at Mount Batchelor Observatory, which is located at an altitude of three thousand meters.
“I thought we could only collect dead biomass,” says Smith, who works as a research scientist at NASA Ames Research Center.
But when his team returned to the laboratory in the spring of 2011, collecting air samples from two large plumes of volcanic ash, scientists found a thriving group of little travelers. More than 27% of bacteria and 47% of fungi from the samples taken were alive.
Ultimately, the team identified nearly 2,100 species of microbes, including Archea microbes, previously found only on the isolated Japanese coast. “In my opinion, this was indisputable evidence,” Smith says. As he likes to put it, Asia sneezed on America.
Context
Earth is a planet of bacteria
Ukraine is young 03/27/2013The eternal battle between bacteria and medicine
SwissInfo 03/01/2015Traces of a supernova in terrestrial bacteria
Nature 04/17/2013Microbes have been found in the skies since Darwin collected samples of airborne dust on the HMS Beagle a thousand miles west of Africa in the 1830s. But new capabilities in DNA analysis, high-altitude sampling and atmospheric modeling are giving scientists new insights into life high above the Earth. For example, recent research suggests that microbes have secret influences on the atmosphere. They collect clouds, cause rain, spread disease from continent to continent, and maybe even change the climate.
“I think the atmosphere is a big track, literally,” Smith said. “It allows ecosystems thousands of kilometers apart to exchange microorganisms, and in my opinion this has much deeper ecological consequences than we think.”
Airborne microbes can have a huge impact on our planet. Some scientists attribute the 2001 outbreak of foot-and-mouth disease in Britain to a giant storm in northern Africa that carried dust and disease spores thousands of miles north. This storm occurred just a week before the first cases of foot and mouth disease were detected on British soil.
Sheep blue tongue virus, which infects domestic and wild animals, was once present only in Africa. But it is now being found in the UK, which may be a result of prevailing winds.
Scientists studying the disappearance of coral reefs in the pristine Caribbean say it's all because of dust and the microbes it carries, which are lifted into the air during sandstorms in Africa and then flown west. They say the sea fan coral-killing fungus first arrived in the Caribbean in 1983, when a drought in the Sahara caused dust clouds to blow across the Atlantic.
In west Texas, scientists from Texas Tech University collected air samples upwind and downwind of 10 cattle feedlots. Samples from the downwind side had 4000% more antibiotic-resistant microbes than those from the windward side. Associate Professor Philip Smith, who specializes in terrestrial ecotoxicology, and Associate Professor Greg Mayer, who specializes in molecular toxicology, say the work has laid the foundation for further research.
They have conducted a study on microbial resistance, which will be published in early 2016, and now want to understand how far particles can travel and whether antibiotic resistance can be transferred to local microbes. Antibiotics, Mayer notes, existed in nature long before humans borrowed them. But what happens when they concentrate in one place or are carried by the wind?
One thing is now clear: there are much more viable microbes in harsh and inhospitable places than researchers thought.
Scientists from the Georgia Institute of Technology, receiving a research grant from NASA, studied air samples taken from an airplane flying high above hurricane zones. They found that living cells accounted for approximately 20% of the number of microbes lifted into the air by the storm.
"We didn't expect to find so many living and intact bacterial cells at an altitude of 10,000 meters," says microbiologist Kostas Konstantinidis of the Georgia Institute of Technology.
Konstantinidis and his colleagues became interested in how microbes contribute to cloud formation and precipitation. The nucleus of an airborne bacterial cell initiates condensation. Some scientists now believe that microbes play an important role in meteorology. “They can actively influence cloud formation and climate,” says Constantinidis.
Smith became interested in how microbes survive and even recover after a long journey in harsh radiation conditions in the upper atmosphere. He led NASA's EMIST (Microorganisms in the Stratosphere) project, which took spore-forming bacteria twice in a balloon 38 kilometers above the New Mexico desert to understand how they survive there.
For NASA, this work involves protecting planets from adverse impacts. If a spaceship infected with terrestrial bacteria flies to Mars, where conditions are similar to the Earth's stratosphere, and the bacteria survive the flight, this will complicate our search for traces of Martian life, and may even destroy the microbes there, if they exist.
But this work also provides broader opportunities. Like researchers of the past who scoured tropical rainforests in search of miracle drugs, today's scientists may one day find a cure in the miniature inhabitants of the atmosphere. Maybe atmospheric bacteria will give us reliable protection from the sun and radiation.
“The amazing thing is that the organism that can survive in extremely harsh environments is, in many cases, single-celled,” Smith says. - How does he manage to do this?
InoSMI materials contain assessments exclusively of foreign media and do not reflect the position of the InoSMI editorial staff.
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The reason people get sick is often the viruses and bacteria that live around them. They are responsible for the spoilage of food and water, for the development of infections and inflammation. One of the means to combat them is temperature. But it affects different types of microorganisms in completely different ways.
What types of microorganisms are there?
All microorganisms are divided into three conditional groups, depending on which temperature range is most suitable for them. Scientists calculate the exact values by observing the growth and reproduction of bacteria or viruses. If these processes occur at maximum speed, then the conditions are most suitable. Thus, scientists highlight:
- Psychrophylls, or cold-loving microorganisms, for which temperatures from -2 to +30 C are best suited. Such bacteria can easily live in your refrigerator. A special membrane shell, which contains a large amount of unsaturated fatty acids and retains its properties in the cold, helps them withstand the cold. This type of microorganism includes, for example, clostridium or mold.
- Mesophylls, which grow and reproduce best in the range from +20 to + 50 C. This group includes most microorganisms, including those that cause infectious diseases in humans. For example, the bacterium Proteus, which can cause gastritis and gastroenteritis.
- Thermophiles, which grow and reproduce best at temperatures of +50 - +60 C, and some of their species can survive at +100 C. Such microorganisms include, for example, actinomycetes, which mainly live in soil and water.
The viruses that most often cause colds and flu are mesophylls. Therefore, in the cold, especially in dry air, they die within a few hours.
At what temperature do microorganisms die?
Why do you need to know at what temperature bacteria die? For example, in order to preserve food from spoilage longer. Or to keep your temperature down when you have a cold. However, even the same microorganisms, depending on other environmental conditions, may have different sensitivity to cold or heat.
Most microorganisms die when heated to +50 C, but only if heating occurs in dry air, but in liquid they can survive at +70 C. In order to protect meat or fish, they will have to be heated to 100 C. A In the human body, most infections die at +37.5–38 C.
In the external environment
The survival of bacteria and viruses in the external environment will depend not only on temperature, but also on what surface they are on and at what humidity. For example:
- Cold and flu pathogens can survive on smooth surfaces from 15 hours to two to three days. True, their ability to cause disease decreases sharply after 24 hours. The causative agents of intestinal infections, such as salmonella or E. coli, can remain active for up to 4 hours. Staphylococcus aureus up to several weeks.
- On the surface of the skin, viruses and bacteria die quite quickly. Approximately 40% of them die within an hour. For example, herpes lasts on the skin for a maximum of two hours, and the flu pathogen lasts no longer than 30 minutes.
- In the air, microorganisms that cause flu and colds do not persist for as long as is commonly believed. The influenza virus will die within five hours, especially in clear sunny weather, when it is also exposed to ultraviolet radiation from the sun. The infection will survive a little longer in frosty weather.
- Bacteria and viruses survive the longest in water and soil. Salmonella can live in water for 72 hours, in soil for up to two months, and Vibrio cholerae for up to 13 days.
In order to avoid most infections, including those that cause acute respiratory diseases, it is enough to wash your hands after you come from the street, additionally rinse your nose with special sprays and keep the house clean.
In the human body
For most pathogens of infectious diseases, it is the internal environment of the human body that is ideal. The same influenza virus multiplies especially well in a humid environment and at a temperature of +36–37 C. That is, in the conditions that exist in your respiratory system. Moreover, in the human body it can persist from five to ten days, depending on the state of immunity and the treatment performed. That is why the minimum course of taking antiviral drugs is five days.
As for the fever that torments you during illness. Then numbers at + 38 and even at +40 C cannot kill the virus itself. However, this temperature blocks the ability of the pathogen to penetrate new cells and multiply. In addition, it is the elevated temperature that triggers the body’s production of interferon, a special protein that actually destroys the virus.
Air as a habitat for microorganisms is less favorable than soil and water, since it contains very little or no nutrients for the proliferation of microorganisms. However, once in the air, many microorganisms can remain in it for more or less a long time. Microorganisms are distributed unevenly in the air. There are more microorganisms in dusty and dirty air than in clean air, since they are adsorbed on the surface of solid particles. The air is especially polluted near the earth's surface, and as it moves away from it it becomes increasingly cleaner. There are more microorganisms in the air of the city center, and fewer in the outskirts. In summer there are more microorganisms in the air, in winter there are fewer.
Microorganisms have even been found in clouds. At high altitudes, microorganisms are found that form pigments, which increase their resistance to unfavorable living conditions, especially ultraviolet rays. Microorganisms are not found above 84 km above sea level.
Number and species composition of microorganisms in the air . Under natural conditions, hundreds of species of saprophytic microorganisms are found in the air, represented by cocci (including sarcina), spore-forming bacteria and filamentous fungi, which are highly resistant to ultraviolet rays and other adverse environmental influences. The air in open spaces is relatively clean, while the air in closed spaces is much more polluted. In the air of enclosed spaces with poor ventilation, microorganisms released through the human respiratory tract accumulate. Pathogenic microorganisms enter the air from phlegm and saliva when coughing, talking, or sneezing. Even a healthy person releases 10...20 thousand CFU into the air when sneezing and coughing, and a sick person releases many times more.
The number of microorganisms in the air varies over wide ranges: from single bacteria to tens of thousands of CFU/1m3. Thus, the Arctic air contains 2...3 CFU per 20 m 3, and in cities with industrial enterprises a huge number of bacteria are found in the air. In a forest, especially a coniferous one, there are very few microorganisms in the air; forest phytoncides have a detrimental effect on them. Above Moscow at an altitude of 500 m in 1 m 3 of air, from 1100 to 2700 CFU of microorganisms were found, and at an altitude of 2000 m – 500-700 CFU. Spore-forming bacteria and filamentous fungi were found at an altitude of 20 km, other groups of microorganisms - at an altitude of 61...77 km.
On average, a person inhales 12,000...14,000 dm 3 of air per day. At the same time, 99.8% of microorganisms contained in the air are retained in the respiratory tract.
Air pollution by pathogenic microorganisms . When you sneeze, cough or talk, many droplets of liquid containing microorganisms are released into the air. These droplets can remain suspended in the air for hours, i.e. form persistent aerosols. Due to moisture, microorganisms in droplets live longer. Infection with many acute respiratory diseases (influenza, measles, diphtheria, pneumonic plague, etc.) occurs through this airborne route. This way of spreading pathogens is one of the main reasons for the development of not only epidemics, but also major pandemics of influenza, and in the past, pneumonic plague.
In addition to airborne droplets, pathogenic microorganisms can spread through the air via dust. This is explained by the fact that the microorganisms found in the secretions of patients (drops of sputum, mucus, etc.) are surrounded by a protein substrate, so they are more resistant to drying out and other factors. When such droplets dry, they turn into a kind of microbial dust containing many pathogenic microorganisms.
Microbial dust particles have a diameter from 1 to 100 microns. For particles with a diameter of more than 100 microns, gravity exceeds air resistance and they quickly settle. The speed of dust transfer depends on the intensity of air movements. Microbial dust plays a particularly important role in the epidemiology of tuberculosis, diphtheria, tularemia and other diseases.
To reduce microbial contamination of the air in production areas physical methods are used to clean and disinfect it. With the help of a supply and exhaust ventilation system, polluted air is removed from the premises, and cleaner atmospheric air enters in its place. Filtration of incoming air through special air filters significantly increases the efficiency of ventilation.
The most widely used method is filtering air through fibrous porous or granular materials. Although fiber filters have a diameter of at least 5 microns and a weak seal (gaps of at least 50 microns), they easily retain most microorganisms with an average size of about 1 micron.
Filters impregnated with a special dust-binding liquid trap up to 90-95% of microorganisms and dust particles in the air. After cleaning, the air is disinfected. Using fine air filters (FPO) you can achieve cleaning efficiency of up to 99.999%. The required degree of indoor air purification is determined by the conditions and nature of the product being manufactured. Modern equipment for biological air purification ensures the organization of general and special areas. A biological air purification line, as a rule, includes several technological elements operating in series: an oil filter, a coarse filter, a head filter and individual fine filters. The set of individual elements in the system is determined by the specific production task.
Disinfected air can be obtained using UV irradiation. For this purpose, the room is equipped with stationary or portable bactericidal lamps at the rate of 2.0-2.5 W/m 3 of room volume. Operating the lamps for 6 hours can reduce the number of microorganisms in the air by 80-90%. However, it should be borne in mind that the operation of conventional lamps should be carried out in the absence of people, since their radiation has an adverse effect on the skin, mucous membranes of the body and eyes. Air disinfection in the presence of people can only be carried out using ultraviolet bactericidal irradiators-recirculators, which are designed for periodic and continuous operation.
Typically, the air in the production premises of food enterprises should contain no more than 500 CFU/m3. For some industries, the permissible levels of microorganisms in the air are more stringent; their values are given in regulatory documentation.
Air sanitary assessment. To determine air microorganisms, the following methods are used:
sedimentation (Koch method), filtration (air is passed through sterile water);
methods based on the principle of the impact action of an air jet using special instruments. The latter methods are more reliable, since they allow one to accurately determine the quantitative air pollution by microorganisms and study their species composition.
At food industry enterprises, in production workshops and in food storage areas, it is necessary to maintain certain humidity, temperature and microbiological purity of the air.
The sanitary assessment of indoor air is carried out according to the following indicators: KMAFAnM (the number of mesophilic aerobic and facultative anaerobic microorganisms); content of mold (mycelial) fungi and yeast; the number of sanitary-indicative streptococci in 1m3 of air.
The number of cells (CFU) in 1 m 3 of air is used to judge the degree of streptococcus contamination of human nasopharyngeal microorganisms and, therefore, the possible presence of pathogenic microorganisms in the air.
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.
Despite the fact that the atmosphere is an unfavorable environment for the development of microorganisms, the latter are constantly present in it. The conditions existing 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, nitrogen and carbon gases and other elements. Microorganisms enter the atmosphere along with dust. They remain there for some time in a suspended state, and then partially settle to the ground, while some die from direct sunlight and drying out. In dry, sunny weather, microbes die en masse. Due to this, the air microflora is sparse. It depends on the microflora and the condition of the soil above which the air layer under study is located. Cultivated soil rich in organic matter contains far more microbes than soil in barren deserts or snow-covered fields.
In terms of qualitative composition, the air microflora is dominated by various pigment forms that produce colored colonies on dense media. This is due to the fact that colorless microbes are more sensitive to the bactericidal effect 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 yeasts, mushrooms, sardines, staphylococci and various spore rods. There are few non-spore-bearing rod-shaped bacteria in the air, as they have low resistance to drying. Pathogenic microbes may also be present in the air of residential premises and especially in the environment of patients.
The number of microorganisms and their composition in the air varies depending on many conditions. Dry soil, its atomization and winds sharply increase the degree of air pollution by microbes. Precipitation significantly cleans the air. The least number of microbes is in the air above forests, seas and snow. According to research by B. L. Isachenko, the air above places covered with snow all year round can be considered absolutely clean. Under such conditions, 1-2 microbes settle on a bacterial cup per hour.
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 of 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 upward, their number decreases.
The content of microbes in the air also depends on the time of year. There are fewer of them in winter and more in summer, since in winter the soil is covered with snow and the air does not come into direct contact with it. In summer, the wind raises dust from the ground, and with it a mass of microbes. The air population in spring and autumn occupies an intermediate position between the summer and winter populations, since at this time it often rains and the wind raises less dust from the moist soil.
The air of indoor spaces in winter, on the contrary, is richer in microorganisms than in summer. This is explained by the fact that in winter a person spends most of his 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 admixtures of gaseous and vaporous products. The smallest drops of liquid can adsorb various organic substances entering the air, and thus enable microorganisms located in the drops to multiply. Thus, the air environment provides not only the temporary residence of microorganisms there, but sometimes even favors their development.
Microorganisms contained in the air can cause various infectious diseases - influenza, sore throat, measles, scarlet fever, etc.
Microbiological study of atmospheric air, as well as indoor air, occupies an important place in purifying it from bacterial contamination as a measure to combat aerogenic infections.
Currently, much attention is paid to the study of atmospheric microbiology in connection with space exploration.
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