Microbial Diversity in Uranium Deposits from Jaduguda and Bagjata Uranium Mines, India as Revealed by Clone Library and Denaturing Gradient Gel Electrophoresis Analyses

Microbial communities within subsurface uranium (U) deposits were explored to understand the nature of community composition and their potential role in biogeochemical cycle and bioremediation. Geochemical analysis revealed that the U ores were mainly hosted on metamorphosed chlorite-biotite schists, containing varied organic carbon and elevated level of several heavy metals (U, Cu, Cr, Zn, etc.). Microbial diversity as explored by 16S rRNA gene clone library and DGGE analyses revealed predominance of <i>Proteobacteria</i>, <i>Acidobacteria</i>, <i>Bacteroidetes</i> along with <i>Firmicutes</i> and candidate division OP9 within the domain <i>Bacteria</i> and <i>Euryarchaeota</i> within the domain <i>Archaea</i>. Among the physiochemical parameters, level of organic carbon showed considerable impact on influencing community diversity and composition. Samples from Jaduguda with high organic carbon showed abundance of bacteria known for metabolizing different carbon compounds and affiliated to unclassified uncultured members of <i>Chitnophagaceae</i> (<i>Bacteroidetes</i>), Gp4 of <i>Acidobacteria</i> and unclassified β-<i>Proteobacteria</i> and halophilic, nitrate-reducing γ-<i>Proteobacteria</i>. A relatively diverse assemblage of species capable of autotrophic/heterotrophic N₂ fixation, CH₄ utilization, H₂(0)/Fe(II)/Mn(II)/S(0) oxidation, NO₃/Fe(III) reduction, U and other metal precipitation/mineralization and affiliated to families <i>Rhizobiaceae, Bradyrhizobiaceae, Caulobacteraceae</i>, <i>Comamonadaceae</i> and genera <i>Acinetobacter, Marinobacter</i> and <i>Alcanivorax</i> constituted the Bagjata samples. Distribution and interrelations among abundance of various bacterial groups detected in other U mines/radioactive waste sites were compared with our data. Overall, the study reported distinct compositions of indigenous microbial communities among the samples from two mines and provided a better insight in geomicrobiology of U deposits.