Microbial Dynamics and Diversity of Bacillus thuringiensis in Textile Effluent Polluted and Non-polluted Rice Field Soils of Orissa, India

Abstract

Microbial diversity was assessed in the soils of non-polluted rice fields of Central Rice Research Institute and Choudwar, and textile effluent contaminated (about 30years) rice fields of Choudwar about 4years after cessation of pollution. The soils contained 0.62-1.01% organic C and 0.07-0.12% total N, and measured 6.18-8.24 pH and 0.6-2.68mS/cm Eh which were more in the polluted Choudwar soil. The microbial populations (×10(6)cfu/g soil) in the soils were: heterotrophs 1.21-10.9, spore formers 0.9-2.43, Gram (-)ve bacteria 4.11-8.0, nitrifiers 0.72-1.5, denitrifiers 0.72-2.43, phosphate solubilizers 0.14-0.9, asymbiotic nitrogen fixers 0.34-0.59, actinomycetes 0.07-0.11, fungi 0-0.5 and Bacillus thuringiensis (Bt) 0.4-0.61 which predominated in the polluted soil of Choudwar. The fungi were scarce in the polluted rice fields. The Bt isolates belonged to three motile and one non-motile group. Two motile Bt isolates were phenotyped as Bt subsp. sotto and israelensis, whereas, the non-motile isolate was Bt subsp. wahuensis. All Bt isolates produced extracellular protease, lipase and amylase enzymes. The microbial guilds had positive correlation among themselves, as well as, with soil physico-chemical characters but the fungi had negative relation and the nitrogen fixers were unrelated with the biotic and abiotic components.