BY: K. Sai Manogna (MSIWM014)


The study of living microbes that are suspended in the air is known as Aero microbiology. Such microbes are known as bioaerosols. There are significantly fewer microorganisms in the atmosphere than in the oceans and in the soil; there are still many microorganisms that can impact the atmosphere. With the help of wind and precipitation, these microbes have a chance to migrate long distances and increase the rate of infectious diseases caused by these microbes. In humans, animals, and plants, these aerosols are ecologically important because they can be associated with the disease. Microbes can suspend themselves in the atmosphere, where they can communicate and precipitate with the clouds and create specific shifts in the clouds. 

The air has two microbial ecosystems. 

A. Atmosphere 

B. Clouds 

A. Atmosphere: 

1. High light intensities, extreme temperature fluctuations, low amount of organic matter, and a lack of water availability; characterize the atmosphere as a habitat, making it a non-hospitable environment for microorganisms and a generally inadequate habitat development. 

2. In the lower regions of the atmosphere, however, large numbers of microbes are contained. 

B. Clouds: 

1. In the atmosphere, an apparent mass of concentrated watery vapor floating, usually well above the general ground level. 

2. Clouds, with a pH ranging from 3 to 7, are also an acidic environment. 

Sources of airborne microorganisms: 

1. Air is not a favourable microbial growth environment because it does not provide adequate moisture and nutrients to sustain growth and reproduction, and there is also no indigenous flora growth in the air. 

2. Quite a range of sources responsible for introducing microbes into the air have been identified and researched. 

3. The most popular of these is dirt. Microbes are suspended in the air with wind flow and remain there and often accumulate. 

4. Microbes are often released into the air by human activities such as digging, sloughing, and running. 

5. Microbes are often released into the air through air currents and splashes of water. 

6. Besides, air currents strip plant and animal pathogens from their surfaces and disperse them across the atmosphere. 

7. In contrast to animal pathogens, plant pathogens can spread more quickly. For example, a gamine flies over a thousand kilometers with Puccini spores.

Examples of airborne plant pathogens:

Examples of airborne animal pathogens:

8. Human beings are the primary cause of the introduction of bacteria into the air.

Examples of airborne human pathogens:

9. The most comprehensive source is human activity. The pathogenic bacteria in the human respiratory tract and the mouth’s microbes are continuously released into the air, but they cough, sneeze, and laugh. 

Depending on the size and moisture content, the microbes released into the air come in three forms. Those are the three forms: 

1. Droplets 

2. Nuclei Droplets 

3. Dust that is contagious 

Droplets: As we sneeze, millions of droplets are released, and mucus is expelled from about 200 miles away. Such droplets are water droplets that hold microorganisms if a diseased individual releases them. Saliva and mucus comprise these droplets. Most of the microorganisms they transport are from the respiratory tract. The droplet size determines how long microorganisms live on the droplet. Large-sized droplets settle quickly in the air. The source of these droplets carrying the microorganism can be a source of infectious disease. 

Nuclei Droplets: 

Water particles emitted 1 to 5 micrograms in diameter during sneezing and coughing. For respiratory disorders, droplet nuclei are known to be the raw material. On its surface, it contains saliva and mucus. They are stuck in the air for a more extended period because of their small scale. Droplet nuclei, if the bacteria are the constant source of bacterial infections, are known to be 

The present remains viable on its surface. The viability of bacteria depends on physical conditions, such as humidity, sunlight, moisture, and droplet size. 

Dust Particles: 

By bed making, holding a handkerchief, working with a patient with dried secretion, digging and ploughing, these dust particles are released into the air. Microorganisms adhere to these droplets’ surface and are then suspended by the above techniques to dry them. There is a more significant size of dust particles laden with bacteria and settle down in the air. Two forms of droplets cause airborne diseases. 

a. Droplet infection due to droplets with a diameter greater than 100-micron meters. 

b. Any dried droplet residues cause airborne infections. 

Infection with droplets remains localized and concentrated, while airborne infection may be long-distance. Microorganism can grow on dust particles for a more extended period. It is proven harmful in hospitals and laboratories when closed bottles of dried specimens are opened, and cotton plugs are removed from the bottles. 

Factors influencing airborne microbes:

Factors that influence microbial survival in the atmosphere are 

a. Temperature

b. Moisture/Humidity

c. Content of Nutrients 

d. pH and Acidity 

1. The main factor in regulating the growth of microbes in the air is temperature. 

2. High temperatures hinder the production of microbes and often denature the microbes’ structural conformation. 

3. Very few microbes can live and withstand high temperatures, i.e., extremophiles. 

4. Likewise, when ice crystal formation occurs, shallow temperatures are also not ideal for microbial growth. 

5. Humidity has a role in preserving the development of airborne microbes. 

6. Gram-Bacteria associated with aerosols tend to live in low humidity for a more extended period. 

7. The abundance of nutrients in the atmosphere is lower, so it does not help microbial growth. 

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