Different microbiome
and Bacillus thuringiensis diversity and dynamics of field soils of sole rain
fed rice, and deep/shallow water rice-fish cultivation systems of National Rice
Research Institute was assessed to enrich knowledge on functionalities of
active microbial guilds of aforementioned micro-ecologies. Diversity and
dynamics (x105 cfu/g soil, approx.) of microbial guilds viz.
heterotrophs (1.04-7.87), spore formers (0.37-0.99), Gram negative bacteria
(0.87-9.44), asymbiotic N2 fixers (0.10-0.17), nitrifiers
(0.04-0.38), denitrifiers (0.09-0.38), spore crystal formers (0.003-0.02),
actinobacteria (0.004-0.005) and fungi (0.003-0.01), as well as, indices
(0.07-0.19 x 10-2) of spore-crystal forming bacteria i.e. Bacillus
thuringiensis (Bt) were highly diverse in rain fed rice and deep/shallow water
rice-fish farming field soils. Four spore-crystal forming bacterial isolates
viz. TB426 and 432 of rice field, and TB436 of deep water rice-fish and TB442
of shallow water rice-fish farming field soils were diverse in phenotypic
characters, antibiotic/salt (6–11% NaCl) tolerance, crystal composition
(bipyramidal but variable sizes) etc. The Bt isolates (Bts) had 62.10-76.87 kbp
genomic DNA (gDNA) and single plasmid (24.33- 42.50 kbp). The Bts (TB 426/432)
had 12-14 cellular proteins (9.88-540.7 kDa). Phenotypic identities of TB426
and 432 were Bacillus thuringiensis (Bt) var. galleriae, TB436 was Bt var.
thompsoni/coreanensis and TB442 was Bt var. dendrolimus/sotto. The results
proved structural and functional diversity of Bt population in NRRI rice soils
of different micro-ecologies. The resident Bt with different toxin composition
would be potent natural biocide and can be exploited for suppression of
different rice field pests to sustain productivity.
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