Aeromicrobiology - microbewiki (2022)



  • 1 Introduction
  • 2 Physical Environment
    • 2.1 Atmosphere
    • 2.2 Clouds
    • 2.3 Physical Environment Stresses
  • 3 Microbial Communities
    • 3.1 Bacterial
    • 3.2 Fungal
    • 3.3 Viral
  • 4 Microbial Processes
    • 4.1 Droplet Formation
  • 5 Current Research
  • 6 References


Aeromicrobiology is the study of living microbes which are suspended in the air. These microbes are referred to as bioaerosols (Brandl et. al, 2008). Though there are significantly less atmospheric microorganisms than there are in oceans and in soil, there is still a large enough number that they can affect the atmosphere (Amato, 2012). Once suspended in the air column, these microbes have the opportunity to travel long distances with the help of wind and precipitation, increasing the occurrence of widespread disease by these microorganisms. These aerosols are ecologically significant because they can be associated with disease in humans, animals and plants. Typically microbes will be suspended in clouds, where they are able to perform processes that alter the chemical composition of the cloud, and may even induce precipitation (Amato 2012).

Physical Environment

There are many factors within the physical environment that affect the launching, transport and deposition of bioaerosols. Particles which become suspended in the air column arise mainly from terrestrial and aquatic environments and are typically launched by air turbulence (Pepper 2011). Winds are the primary means of transport for bioaerosols. Bioaerosols can be deposited by a number of mechanisms, including gravity pulling them down, making contact with surfaces, or combining with rain which pulls the particles back down to earth's surface (Pepper 2011).


Along with water droplets, dust particles and other matter, air contains microbes (Al-Dagal 1990). Microbes follow a particular pathway in which they are suspended into the atmosphere. First they are launched into the air. The source of the launching of airborne microbes stems from humans, animals and vegetation. (Al-Dagal 1990). then they are transported (by various methods including winds, machinery and people) and finally are deposited somewhere new. The atmosphere can have a variety of physical characteristics, and can be very extreme in terms of the relative humidity, temperature and radiation. These factors play a huge role in what kinds of microbes will survive in the atmosphere and how long they will stay alive (Pepper 2011).


One area that bioaerosols can be found in is within clouds. Cloud water is a mixture of organic and inorganic compounds suspended within moisture (contribution of microbial activity yo clouds). The conditions in clouds are not conducive to much life, as microbes present there must withstand freezing temperatures, the threat of desiccation, and extreme UV rays. Clouds are also an acidic environment, with a pH ranging from 3 to 7. Nevertheless, there are extremophile microbes which can withstand all of these environmental pressures. Clouds serve as a transport for these microbes, dispersing them over long distances (Amato 2012).

(Video) Ocean Atmosphere Interactions | GEO GIRL

Physical Environment Stresses

The atmosphere is a difficult place for a microbe to survive. Dessication is the primary stress that aeromicrobes face, and it limits the amount of time that they can survive while suspended in the air (Pepper 2011). Humidity within the air is a second factor which can affect the survival of organisms. Certain bacteria, including Gram + bacteria, are more tolerant of high humidity in the air, while others are more tolerant of dessication and dry conditions, such as Gram + cells (Pepper 2011). Temperature must be in an intermediate range, as too hot of temperatures can denature proteins, and too cold of temperatures can cause ice crystal formation (Pepper 2011). Finally, radiation poses a potential hazard for aeromicrobes, as it can damage DNA within the cells.

Microbial Communities

Many different microorganisms can be in aerosol form in the atmosphere, including viruses, bacteria, fungi, yeasts and protozoans. In order to survive in the atmosphere, it is important that these microbes adapt to some of the harsh climatic characteristics of the exterior world, including temperature, gasses and humidity. Many of the microbes that are capable of surviving harsh conditions can readily form endospores, which can withstand extreme conditions (Al-Dagal 336).

Many of these microorganisms can be associated with specific and commonly known diseases. Below are two tables. Table 1 below shows examples of Airborne Plant pathogens, and Table 2 shows examples of airborne human pathogens.


One such bacterial microorganism that can resist environmental stresses is Bacillus anthracis. It is a gram positive rod shaped bacteria that utilizes spore formation to resist environmental stresses. The spore is a dehydrated cell with extremely thick cell walls which can remain inactive for many years. This spore makes Bacillus anthracis a highly resilient bacteria, allowing it can survive extreme temperatures, chemical contamination, and low nutrient environments (Gatchalian 2010). This bacteria is associated with Anthrax, which is a severe respiratory disease that infects humans.


Another such microorganism that can resist environmental stresses is Aspergillus fumigatus, which is a major airborne fungal pathogen (McCormick 2010). This pathogen is capable of causing many human diseases when conidia are inhaled into the lungs. While A. fumigatus lacks virulence traits, it is very adaptable to changing environmental conditions and therefore is still capable of mass infection. (McCormick 2010).


An example of a viral airborne pathogen is the Avian Influenza Virus, which is a single stranded RNA visur that can infect a broad range of animal species as well as humans and cause the Avian Influenza.

Table 2: Examples of Airborne Human Pathogens. Table from Maier, chapter 5

Microbial Processes

The figure on the bottom right depicts the processes that a microbe undergoes during its life cycle. The microbes undergo the emission process, in which they are emitted from surfaces such as water, soil or vegetation and become airborne and transported into the airstream. The red boxes indicate some of the harsh environmental conditions that the microbes must withstand while airborne. The microbes that are able to withstand and survive these environmental pressures are the more resistant varieties. The microbes make it into clouds, where they can begin the breakdown of organic compounds. Finally, the microbes are "rained" out of the clouds through wet deposition, and they begin colonization of their new location (Amato 2012).

Droplet Formation

The emission process mentioned above, in which microbes are lifted in the air often involves microbes being suspended in droplets, which are large enough to keep the microbes hydrated and large enough to maintain a virulent amount of pathogen, but are still small enough to stay suspended in the air (Robinson 2012).

Current Research

Studies about bioaerosols are difficult to conduct because identifying specific microbes and fungi in the air is a daunting task. One study conducted by Mark Hayes and associated looked into the feasibility of identifying specific particles in the air using fingerprinting techniques. It discussed sampling and analysis techniques that can help to identify cellular material. This is important because the particles in the air are information rich and can tell us a lot about where they originated or certain biochemical information about the organisms (Hayes 2012).

A great deal of the research conducted on bioaerosols studies their effects on humans, since human disease is one of the effects of bioaerosols. One such study conducted by Brandl and associates studied the distribution and dynamics of particles within the air in a lecture hall. Knowing what is in the air is important as human mortality rates increase with the rise of airborne particulate populations (Brandl 2008). Additionally, people are continually spending more time indoors, and knowing what exists within the air they breathe is important. This study found that bioaerosol populations were highest when there were a great deal of students in the hallways and the lecture area, proving that humans are a vector for the transport of bioaerosols.

Another study conducted this year by Vinni Hansen looked into components in both greenhouses and open fields to see which affected the levels of fungal bioaerosols. This study was conducted primarily to determine which is more detrimental to farmworkers. The study concluded that the bioaerosol levels were related to the environment, the work tasks, and the vegetable crops.


al-Dagal, M., & Fung, D. Y. (1990). Aeromicrobiology--a review. Critical Reviews in Food Science and Nutrition, 29(5), 333-340. Retrieved from

Amato, Pierre. "Clouds Provide Atmospheric Oases for Microbes." Microbe Magazine: n. pag. American Society for Microbiology. Web. 1 Apr. 2012. <>.

Brandl, Helmut, et al. "Short-Term Dynamic Patterns of Bioaerosol Generation and Displacement in an Indoor Environment." International Journal of Aerobiology (Oct. 2008): n. pag. Academic Search Premier. Web. 1 Apr. 2012.

Gatchalian, N.G., et al. "Dry Thermal Resistance Of Bacillus Anthracis (Sterne) Spores And Spores Of Other Bacillus Species: Implications For Biological Agent Destruction Via Waste Incineration." Journal Of Applied Microbiology 109.1 (2010): 99-106. Academic Search Premier. Web. 22 Apr. 2012.

Hayes, Mark et al. "Exploring The Feasibility Of Bioaerosol Analysis As A Novel Fingerprinting Technique." Analytical & Bioanalytical Chemistry 403.1 (2012): 15-26. Academic Search Premier. Web. 10 Apr. 2012.

Madsen, Anne Mette et al. "Factors Affecting Vegetable Growers’ Exposure To Fungal Bioaerosols And Airborne Dust." Annals Of Occupational Hygiene 56.2 (2012): 170-181. Academic Search Premier. Web. 10 Apr. 2012.

McCormick, Allison, Jürgen Loeffler, and Frank Ebel. "Aspergillus Fumigatus: Contours Of An Opportunistic Human Pathogen." Cellular Microbiology 12.11 (2010): 1535-1543. Academic Search Premier. Web. 22 Apr. 2012.

Pepper, Ian L., and Scot E. Dowd. "Aeromicrobiology." Environmental Microbiology. N.p.: Academic Press, 2009. 83-101. Print.

Robinson, Marguerite, Nikolaos Stilianakis, and Yannis Drossinos. "Spatial Dynamics of Airborne Infectious Diseases." Journal of Theoretical Biology 297 (Mar. 2012): 116-126. Print.

Saber, Hamed. Clouds. August 22, 2011. "The Long Strange Journey of Earth's Microbes." Matte Network. Web. 10 Apr. 2012. <>.

Edited by Anne Logisz, a student of Angela Kent at the University of Illinois at Urbana-Champaign.


What is Aeromicrobiology pathway? ›

Aeromicrobiological Pathway. The aeromicrobiological pathway describes: (1) the launching of bioaerosols into the air; (2) the subsequent transport via diffusion and dispersion of these particles; and finally (3) their deposition.

Why is Aeromicrobiology important? ›

[7] The microbiology of air is significant in many places such as hospitals, food processing, air conditioning and many other places. Air Microflora Significance in Hospitals and Source, significance, and control of indoor microbial aerosols: human health aspects. both give examples of the significance.

What are the five basic techniques the 5 I's microbiologist use to work with microbes? ›

Culture Techniques

There are five basic microbiology lab procedures (Five “I's”) that are utilized by the microbiologists to examine and characterize microbes namely Inoculation, Incubation, Isolation, Inspection (Observation), and Identification.

What are the factors affecting air microflora? ›

The factors that affect air microflora include atmospheric temperature, humidity, air current, the height at which the microorganisms are found etc.

How do you isolate microorganisms from soil? ›

Bacteria present in soil can be isolated by several methods.
  1. Soil dilution/ 24-48 hour nutrient broth culture of Staphylococcus, Streptococcus, Escherichia coli.
  2. Nutrient agar plates.
  3. Inoculating loop.
  4. Bunsen burner/Laminar clean air flow.
  5. Glass marking pencil.
  6. Incubator.

How do you isolate bacteria in the air? ›

Principle. The Isolation of Microorganism From Air is performed by using the settle-plate technique. In this method a suitable medium is poured over a sterile petri dish and then allow it to slidify. After that the plate is exposed to the open air for a few minutes.

Is there good bacteria in air? ›

The air you breathe is teeming with more than 1,800 kinds of bacteria, including harmless relatives of microbes associated with bioterrorist attacks, according to a new study.

How do microbes affect the environment? ›

The most significant effect of the microorganisms on earth is their ability to recycle the primary elements that make up all living systems, especially carbon (C), oxygen (O) and nitrogen (N). These elements occur in different molecular forms that must be shared among all types of life.

What microbes are found in water? ›

Of the many infectious microorganisms found in the environment, bacteria (such as Shigella, Escherichia coli, Vibrio, and Salmonella), viruses (such as Norwalk virus and rotaviruses), and protozoans (such as Entamoeba, Giardia, and Cryptosporidium) may be found in water.

Is microbiology hard in college? ›

Microbiology is a hard subject to study. It's very detail heavy; requiring you to remember a lot of facts about microscopic organisms, morphologies and modes of action. Without some basic knowledge of biology and chemistry, or the ability to memorize things easily, it's likely you'll struggle.

Which isolation technique is most effective? ›

Streaking for Isolation Procedure. There are several methods of streaking for isolation. The vast majority of our students have been most successful with the quadrant method of streaking which is described below.

Which bacteria is found in the air? ›

The number of bacteria found ranged from 0.013 to 1.88 organisms per liter of air sampled. Representatives of 19 different genera were found in 21 samples. The most frequently isolated organisms and their percent of occurence were Micrococcus (41%), Staphylococcus (11%), and Aerococcus (8%).

What are the 5 factors that influence microbial growth? ›

CHAPTER 6 - Microbial Growth
  • Physical factors - temp, pH, water, oxygen, pressure.
  • Nutrients - Cell constituents and energy sources.

What are the 6 factors for microbial growth? ›

  • Factor # 1. Solutes and Water Acidity:
  • Factor # 2. Temperature:
  • Factor # 3. pH:
  • Factor # 4. Oxygen Requirements:
  • Factor # 5. Pressure:
  • Factor # 6. Radiation:

Which medium is used for isolation of bacteria from soil? ›

Two culture media were used in both sites to obtain bacterial isolates: SEM and Luria–Bertani (LB) [30]. Briefly, SEM was prepared by mixing agar with an aqueous soil fraction (soil:distilled water, 1:1 p/v). This fraction was obtained using 80 g of soil mixed with 80 mL of distilled water.

How many microorganisms are in a gram of soil? ›

Up to 10 billion bacterial cells inhabit each gram of soil in and around plant roots, a region known as the rhizosphere.

How do you identify microorganisms in soil? ›

By use of the DNA primers and DNA probes which were synthesized by PCR, the homologous metalloprotease gene was detected in DNA directly extracted from soils. The soil microorganisms are considered to be the main source of soil protease.

What are the 3 main methods to isolate bacteria? ›

Following isolation methods are employed to isolate microbes from mixed cultures:
  • Streaking.
  • Plating.
  • Dilution.
  • Enriched procedure, and.
  • Single cell technique.

What is the principle of isolation of bacteria? ›

Isolation of bacteria involves various steps – Specimen collection, Preservation and transportation of specimen, Microscopic examination of sample. Various methods used for isolation of bacteria culture methods which includes culture on solid or liquid media and automated system.

What is the purpose of isolating bacteria? ›

Isolation is done to obtain pure bacterial cultures. Bacteria are usually isolated from fish kidney and spleen; and from the hepatopancreas, lymphoid organ and muscles of shrimp. These tissues are monitor organs that usually harbor the disease-causing bacteria during infection.

What happens if you breath in bacteria? ›

When we breathe in bacteria, cells along our nasal passages release “tiny fluid-filled sacs,” called exosomes, that directly fight the microbes.

Do bacteria live in our lungs? ›

The lungs are not sterile or free from bacteria; rather, they harbor a distinct microbiome whose composition is driven by different ecological rules than for the gastrointestinal tract.

Are probiotics good for lungs? ›

In addition, probiotic use has been associated with lower incidence of ventilator-associated pneumonia [95], reduced respiratory infections in healthy and hospitalized children [96, 97], and reduced duration of infection with the common cold [98].

Can we live without microbes? ›

We wouldn't be able to digest our food properly without our gut bacteria. Crops around the world would start to die without the nutrients generated by microbes. Dead fish would float to the surface of lakes and oceans, and ocean life would be extinguished.

Why are microbes so important? ›

Microscopic creatures—including bacteria, fungi and viruses—can make you ill. But what you may not realize is that trillions of microbes are living in and on your body right now. Most don't harm you at all. In fact, they help you digest food, protect against infection and even maintain your reproductive health.

Where are microbes found? ›

Microbes are tiny living things that are found all around us and are too small to be seen by the naked eye. They live in water, soil, and in the air. The human body is home to millions of these microbes too, also called microorganisms.

What are 3 harmful microbes which come from water? ›

The principle bacteria pathogens that have been shown to cause human intestinal disease associated with drinking water are: Salmonella typhi, Typhoid fever; Salmonella paratyphi-A, paratyphoid fever; other Salmonella species, salmonellosis, enteric fever; Shigella dysenteriae, S.

What bacteria is in dirty water? ›

The presence of coliform bacteria, specifically E. coli (a type of coliform bacteria), in drinking water suggests the water may contain pathogens that can cause diarrhea, vomiting, cramps, nausea, headaches, fever, fatigue, and even death sometimes.

Is tap water safe to drink? ›

In most parts of the United States and Canada, it's safe to drink tap water from public water systems. Tap water that's been properly filtered is equally safe as bottled water and provides you with essential minerals you may not get from bottled water.

How bioaerosols are formed? ›

In most situations, the formation of bioaerosols occurs in the form of complex mixtures of allergens, toxins, and other miscellaneous ones. Exposure to bioaerosols tends to be associated with various health effects (e. g., infectious diseases, acute toxic effects, allergies, and cancer).

What is Aero microflora? ›

Aeromicrobiology is the study of living microbes which are suspended in the air. These microbes are referred to as bioaerosols (Brandl et. al, 2008).

What is mean by air microbiology? ›

Air microbiology is a scientific discipline that concerns the microorganisms, including bacteria, archaea, fungi and viruses, in the atmospheric air. It is a subdiscipline of environmental microbiology.

What is Aeromicroflora? ›

Aim: Study of Aeromicroflora Introduction: Aeromicrobiology is the study of all living microbes (bacteria, fungi, viruses, yeast.

How do you sample bioaerosols? ›

Filtration and filter-based samplers. Filtration is one of the most commonly used methods to capture airborne particles, including bioaerosols, because it is convenient and easy to use. Once the bioaerosol particles are collected on a filter, they can be eluted into liquid for subsequent analysis by various techniques.

Where do bioaerosols thrive? ›

Bioaerosols grow in moisture films on surfaces. Several studies have suggested that bioaerosols may contribute to occupant discomfort through several different mechanisms: irritant emissions; release of fragments, spores, or viable organisms leading to allergy; and secretion of complex toxins.

What is the fate of bioaerosols? ›

Fate of bioaerosols in atmosphere

Loading of microorganisms occurs in higher degree from terrestrial sources than aquatic sources. The airborne particles may get released and transported by wind current from various point sources, area sources or line sources.

Why are microbes found in air? ›

Unlike soil microbes, which can be regarded as native to their environment, microbes found in the air only get there by being introduced from another source. Indeed, certain human activities, such as waste disposal, waste treatment, agriculture and industry, have the potential to release microbes into the air.

What are kind of microbes found in air? ›

The number of bacteria found ranged from 0.013 to 1.88 organisms per liter of air sampled. Representatives of 19 different genera were found in 21 samples. The most frequently isolated organisms and their percent of occurence were Micrococcus (41%), Staphylococcus (11%), and Aerococcus (8%).

Who is regarded as father of aerobiology? ›

Philip Gregory has been called the father of modern aerobiology and it was his inspiration that initiated work on air sampling resolving many basic principles (Hirst, 1990, 1992; Lacey et al., 1997).

How many microbes are in the air? ›

The air you breathe is teeming with more than 1,800 kinds of bacteria, including harmless relatives of microbes associated with bioterrorist attacks, according to a new study.

Can bacteria grow in air? ›

Humans and outdoor air are likely to be the major sources of airborne bacteria as well as bacteria growing in indoors (Burrows et al., 2009; Fahlgren et al., 2010; Bowers et al., 2013).

Who Discovered air microbiology? ›

The existence of microscopic organisms was discovered during the period 1665-83 by two Fellows of The Royal Society, Robert Hooke and Antoni van Leeuwenhoek.

What is water microbiology? ›

Definition. Water microbiology is the scientific discipline that is concerned with the study of all biological aspects of the microorganisms (bacteria, archaea, viruses, fungi, parasites and protozoa) that exist in water.

How do you study microorganisms? ›

The Microscope

The principal way a microbiologist studies microorganisms is by observing them through a microscope. A microscope is a device that enlarges objects using a process called magnification.

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