Population dynamics of soil microbes and diversity of Bacillus thuringiensis in agricultural and botanic garden soils of India

摘要

Different microbial guilds of three rice fields (aerobic (dry or wet) laterite and red sandy, and anaerobic (flooded), clay-loam), a botanical garden (wet, aerobic, humus) and a sorghum (dry, aerobic, sandy) soil were investigated. Population (x106?cfu/g dr. soil) of the aerobic (3.8 - 26.2) and anaerobic (0.91 - 13.6) heterotrophic, aerobic (1.1 - 3.7) and anaerobic (0.8 - 1.3) spore forming, Gram (-)ve (0.3 - 0.7), phosphate solubilizing (0.01 - 0.06), asymbiotic?N2-fixing (0.26 - 0.88), sulfur oxidizing (0.13 - 0.75), sulfate reducing (0.01 - 0.1), nitrifying (0.1 - 0.23) and denitrifying (0.04 - 0.25) bacteria; actinomycetes (0.01x104?cfu/g dr. soil), fungi (0.01 - 0.05x105?cfu/g dr. soils) and?Bacillus thuringiensis?(Bt) (0.13-0.25x106cfu/g dr. soil) population were variable in different soils. Nevertheless, proportions of Bt in relation to spore forming bacteria were comparable (index (5-9) x10-4) and they produced either monotypic (bipyramidal or spherical) or heterotypic (polymorphic-bipyramidal or bipyramidal-rhomboidal) crystals although the bipyramidal crystal producing Bt were predominant in the soils. The bipyramidal crystal producing Bt were diverse in different ecologies, resistant to penicillin group of antibiotics and tolerated 5 - 6% NaCl. Phenotypic characters allowed to group the Bt isolates of botanic garden as?B. thuringiensis?subsp.?coreanensis?and as?B. thuringiensis?subsp.?thompsoni/coreanensis, sorghum fields as?B. thuringiensissubsp.?finitimus?and but those of rice fields as?B. thuringiensis?subsp.?thuringiensis/ shandongiensis, finitimus?and?thompsoni/coreanensis.?The isolates produced 25.78, 25.78, 86.26, 24.73, 68.0, 26.8 and 26.8 kDa proteins and equivalent to Cyt, Cry5 and Cry2 toxins effective against the insects of Diptera and Lepidoptera/Coleoptera.