RELATIONSHIP BETWEEN MICROORGANISMS AND ATMOSPHERE

 RELATIONSHIP BETWEEN MICROORGANISMS AND ATMOSPHERE     

AEROMICROBIOLOGY

·       Aeromicrobiology is the study of living microorganisms which are suspended in the air. These microbes are referred to as Bioaerosols.

BIOAEROSOLS

·       Bioaerosols are a sub-category of particles released from Terrestrial and Marine ecosystems into the Atmosphere.

·       Charles Darwin was the first to observe the transport of dust particles but Louis Pasteur was the first to research microbes and their activity within the air.

·       Bioaerosols include Bacteria, Fungi, Viruses and Pollen.

ATMOSPHERE

·       The Atmosphere of earth is the layer of Gases, commonly known as Air that surrounds the planet earth and is retained by Earth's gravity.

·       Significantly more microorganisms are present in Atmosphere than there are in Oceans and in Soil.

·       Microorganisms follow a particular pathway in which they are suspended into the Atmosphere.

a)     First they are launched into the air. The source of the launching of air borne microbes stems from humans, animals and vegetation.

b)    Then, they are transported (by various methods including winds, machinery and people).

c)     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 microorganisms will survive in the atmosphere and how long they will stay alive.

Percentage of Gases in Atmosphere

a)     Nitrogen                          -             79 %

b)    Oxygen                             -             31 %

c)     Carbon-di-oxide          -             0.034 %

d)    Other Gases                   -             Trace amount

*Other Gases – Neon, Helium, Methane and Krypton.

 

Water Vapour Percentage in Atmosphere

0.25 %

Different Layers of Atmosphere

S.No	Layers of Atmosphere	Kilometers (km) from Earth
1	Exosphere	700 to 10,000 km
2	Thermosphere	80 to 700 km
3	Mesosphere	50 to 80 km
4	Stratosphere	12 to 50 km
5	Troposphere	0 to 12 km

MICROBIAL COMMUNITIES IN ATMOSPHERE

PYSICAL ENVIRONMENTAL STRESS TO MICROORGANISMS IN ATMOSPHERE

·       The atmosphere is a difficult place for a microbe to survive.

1)    Dessication (extreme dryness) is the primary stress that aeromicrobes face, and it limits the amount of time that they can survive while suspended in the air. Certain bacteria, including Gram positive bacteria are more tolerant of high Dessication in the air.

2)    Humidity (concentration of water vapour in air) within the air is a second factor which can affect the survival of organisms. Certain bacteria, including Gram positive bacteria are more tolerant of high humidity in the air.

3)    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.

4)     Radiation poses a potential hazard for aeromicrobes, as it can damage DNA within the cells.

LIFE CYCLE OF MICCROORGANISMS IN ATMOSPHERE

·       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 air stream.

·       The microbes that are able to withstand and survive in the 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

MICROBIAL TRANSMISSION THROUGH CLOUDS

·       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 to 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.

 

DROPLETS TRANSMISSION OF MICROORGANISMS

·       Respiratory droplets are large and are not able to remain suspended in the air thus they are usually dispersed over short distances.

·       "Droplet transmission occurs when Respiratory droplets generated via Coughing, Sneezing or Talking contact susceptible mucosal surfaces, such as the eyes, nose or mouth.

·       Transmission may also occur indirectly via contact with contaminated Fomites with hands and then mucosal surfaces.

The pathogen-containing particles also called “Flugge Droplets” (discovered by Carl Flügge) are 01 - 2 mm in diameter and are reduced by evaporation to Droplet Nuclei – small (smaller than 100 μ in diameter), dry particles that can remain airborne for long periods.