Molecular Characterization of Prokaryotic Communities Associated with Lonar Crater Basalts

The Lonar crater is an unusually well-preserved meteorite impact structure that is located in one of the largest volcanic provinces on Earth (i.e., the Deccan Traps in India). The diversity of endoliths in Lonar crater basalts or Deccan flood basalts is not known. Here, the phylogenetic diversity of endolithic Bacteria and Archaea inhabiting basalts retrieved from four discrete sampling sites on the Lonar crater walls and the lake-bed was assessed using culture-independent molecular methods. Taxonomic classification of 16S rRNA gene sequences from all four basalt samples revealed similarities as well as dissimilarities in the presence or absence of several prokaryotic taxa. Cluster analysis of Denaturing gradient gel electrophoresis fingerprints and UniFrac analysis of clone library sequences suggested substantial variations in bacterial and archaeal diversity between crater-wall and lake-bed sites. Although sequences affiliated to the bacterial phyla Actinobacteria, Acidobacteria and Chloroflexi were relatively more abundant in crater-wall basalts than in lake-bed basalts; the reverse was observed for sequences related to Proteobacteria, Firmicutes, Cyanobacteria and Bacteroidetes. Archaea in crater-wall and lake-bed basalt libraries were almost completely represented by Thaumarchaeota and Euryarchaeota, respectively. Diversity indices and richness estimates suggested the diversity of endolithic Bacteria to be higher than that of Archaea in the Lonar crater basalts. A substantial number of clone library sequences did not affiliate with extant Bacteria and Archaea. The detection of several putative lineages associated with C, N and S cycling suggests that the Lonar crater basalts are colonized by metabolically diverse prokaryotic communities involved in biogeochemical cycling of major elements.