Atmosphere as a Habitat

Microbes and Atmosphere
Part-1
Relationship between Microbes and Atmosphere
Atmosphere as a Habitat
Transport of Spores
Sampling of Air
Launching
Transport of Microorgannisms in Air
Deposition and Adhesion
Types of Deposition
Gravitational Settling
Surface Impaction
Rain and Electrostatic Deposition
Methods of Air Sampling
Impingement
Impaction
Centrifugation
Filtration and Deposition
Sampling Methods and their characteristics

Atmosphere as a Habitat

	Atmosphere as a Habitat Even though atmosphere is a hostile environment for microbes, there are substantial number of microbes in the lower troposphere, where because of thermal gradients there is rapid mixing of air. Movement of the air represents a major pathway for the dispersal of microbes. Several bacterial, viral and fungal diseases are spread through the atmosphere. Temporary locations in the troposphere may provide habitats for microbes. Clouds possess concentrations of water that permit growth of microbes. Light intensities and CO₂ concentration in cloud layers are sufficient to support growth of photo-autotrophs.
In industrial areas, there may even be enough concentration of organic chemicals in the atmosphere to permit growth of some heterotrophs. But conclusive proof is lacking and the practical importance of such life appears to be negligible. Although many microbes that grow in the hydrosphere or lithosphere can become airborne, there are no known autochthonous atmospheric microbes. During dispersal, aquatic and soil microbes may enter and pass through the atmosphere before reaching other favourable aquatic or terrestrial ecosystems. Dispersal through the atmosphere ensures continued survival of many microbes. Microbes in the atmosphere occur as spores soredi cysts and other vegetative resistant structures.
Spores whose primary function is dispersal are known as xenospores. Fungi, algae, some protozoa, Actinomycetes and lichens produce spores that are present in the atmosphere. Viruses are transported through the atmosphere as inactive particles that are functionally equivalent to the dormant spores of living microbes.

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