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Factors Influencing Actinomycete Population in Soil

Factors influencing actinomycete population in soil
Organic matter Actinomycetes are abundant in land having a high organic matter status. When the soil is amended with animal manure and organic manure, their number in the soil increases.

pH Actinomycetes are tolerant to acidity and their number declines below pH5.

Temperature Most actinomycetes are mesophilic and thermophilic. Their numbers are high during composting (since heat is evolved during the decomposition of organic manner). They can tolerate up to 65°C.

Moisture Since most of them are aerobic, actinomycetes cannot withstand waterlogging. Unlike bacteria, they (especially the filamentous forms) can withstand dry conditions. Even in the deserts actinomycetes dominate the other forms.

Depth Filmentous forms found in the A horizon as well as at considerable depth make up a larger segment of the subsurface community, i.e. they are found even in the C horizon, e.g. Nocardia, Streptomyces, Actinoplanes.

Functions They are ineffective competitors since they are fastidious organisms. They are less in number when nutrients are high because of greater competition from bacteria and fungi.

They are heterotrophic feeders. Cellulose is decomposed by many species apart from proteins, lipids, starch and chitin.

Many species have the capacity to synthesise toxic metabolites like antibiotics which are effective against bacteria, fungi and yeasts.

Many species of Streptomyces liberate extracellular enzymes which lyse
bacteria.

Actinomycetes participate in the following processes:
Decomposition of certain resistant components of plant and animal
tissues. They are effective competitors only when resistant compounds remain.

Formation of humus through the conversion of plant remains and leaf litters.

Transformation at high temperature. For example, composting and manuring by thermophilic actinomycetes will be common.

Actinomycetes cause certain plant diseases, e.g. potato scab. They also cause certain human infections like Nocardiosis.

They are important as microbial antagonists and in regulating the composition of soil community.

 
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