Soil contains many kinds of microorganisms. Soil is fundamental and irreplaceable; it governs plant productivity of terrestrial ecosystem and it maintains biogeochemical cycles because microorganisms in the soil degrade, sooner or later, virtually all organic compounds including persistent xenobiotics and naturally occurring polyphenolic compounds. This study deals with the microbial diversity at three sites of traditional paddy field in Peravurani taluk, Thanjavur district, Tamil Nadu. Study period was one year covering all the four seasons viz, Monsoon (October to December), Post monsoon (January – March), Summer (April to June), Pre monsoon (July to september). The physico-chemical properties of collected soil were analyzed. About, 47 different colonies were isolated from the 12 soil samples. The colonies distributed in 24 different bacterial species belonging to the 16 genera were isolated by using Nutrient agar medium and identified by colony, morphological and biochemical test and 23 different fungal species belonging to 9 genera were isolated by using Rose Bengal Agar medium and identified by Lacto phenol cotton blue staining. The predominant bacterial species isolated were Bacillus and Pseudomonas and the predominant fungal species isolated were Aspergillus niger, Aspergillus flavus, Aspergillus fumigates, Aspergillus sydowi, Aspergillus nidulans. From this study inferred the seasonal variation in the nutrient availability, soil microbial population and physico-chemical parameters to comparable levels of microbial richness were observed.
