Author(s):

Daphy Meurial C and K Kumar

Abstract: Culturable anaerobic bacterial populations on paddy field soil were found on the order of 10² CFU^-1 g of soil^-1, and the percentages of spores were usually less than 1% of the total anaerobes. Anaerobic bacteria were isolated from the soil samples by picking up colonies on the roll tube agar. The nitrogen fixing obligate and facultative anaerobes were isolated and characterised from paddy ecosystem. The phylogenetic analysis of 30 isolates based on 16S rRNA gene sequences revealed that the composition of dominant culturable anaerobic bacteria on rice soil was rather simple. Molecular analysis based on 16S rRNA gene sequencing revealed that the anaerobic N₂ fixing bacterial isolates NFTh2 showed maximum similarity with Clostridium pasteurianum. Higher nitrogenase activity was noticed for the screened obligate and facultative anaerobic bacteria and exhibited maximum activity on 132^th day (19.81 n moles of C₂H₄ mg^-1 protein h^-1. In the present investigation, the occurrences of anaerobic nitrogen fixer in the paddy ecosystem and their role in the RSA modulations as influenced by anaerobic nitrogen fixer under gnotobiotic condition have been examined.

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