Microbial Ecology of Sulfur Biogeochemical Cycling at a Mesothermal Hot Spring Atop Northern Himalayas, India.

Sulfur related prokaryotes residing in hot spring present good opportunity for exploring the limitless possibilities of integral ecosystem processes. Metagenomic analysis further expands the phylogenetic breadth of these extraordinary sulfur (S) metabolizing microorganisms as well as their complex metabolic networks and syntrophic interactions in environmental biosystems. Through this study, we explored and expanded the microbial genetic repertoire with focus on S cycling genes through metagenomic analysis of S contaminated hot spring, located at the Northern Himalayas. The analysis revealed rich diversity of microbial consortia with established roles in S cycling such as , , , and (). The major gene families inferred to be abundant across microbial mat, sediment, and water were assigned to as reflected from the reads per kilobase (RPKs) categorized into translation and ribosomal structure and biogenesis. An analysis of sequence similarity showed conserved pattern of both genes ( = 178) retrieved from all metagenomes while other S disproportionation proteins were diverged due to different structural and chemical substrates. The diversity of S oxidizing bacteria (SOB) and sulfate reducing bacteria (SRB) with conserved (r) suggests for it to be an important adaptation for microbial fitness at this site. Here, (i) the oxidative and reductive evolutionary time-scale phylogeny proved that the earliest (but not the first) proteins belong to anaerobic with other () oxidizers, also we confirm that (ii) SRBs belongs to δ- occurring independent lateral gene transfer (LGT) of genes to different and few novel lineages. Further, the structural prediction of unassigned DsrAB proteins confirmed their relatedness with species of (TM score = 0.86, 0.98, 0.96) and (TM score = 0.97, 0.98). We proposed that the genetic repertoire might provide the basis of studying time-scale evolution and horizontal gene transfer of these genes in biogeochemical S cycling.