Culture-independent metagenomic approach to characterize the surface and subsurface soil bacterial community in the Brahmaputra valley, Assam, North-East India, an Indo-Burma mega-biodiversity hotspot.

Soil bacterial communities, which contain the highest level of prokaryotic diversity of any natural environment, are important for ecosystem functioning. A culture-independent metagenomic approach was employed in the present investigation to characterize the diversity of soil bacterial community composition in five geochemically and hydrologically different surface and subsurface soil habitats of Brahmaputra valley, Assam, North-East India, an Indo-Burma mega-biodiversity hotspot. The diversity of soil bacterial community was determined through sequence analysis of 16S-23S intergenic spacer regions (ISR). Polymerase chain reaction (PCR) universal primers, 1406F (5'-TGYACACACCGCCCGT-3') and 155r (5'-GGGTTBCATTCRG-3') were used for amplification of 16S-23S ribosomal DNA intergenic spacers of bacteria. Amplification resulted in an intense array of PCR products approximately ranging in size from 200 to 900 bp. Clear banding patterns were observed in analysed samples using the primer set in combination. A clear change in microbial ISR profile was observed on visual analysis of gel electrophoresis profiles. Fast alignment database searches of PCR amplicons of 16S-23S ISR sequence data revealed that the isolated sequences resembled five major phylogenetic groups of bacteria, namely α-, β- and γ-subdivisions of Proteobacteria, Acidobacterium and Comamonadaceae.