Microbial community structure analysis of hypersaline niches and elucidation of their role in the biogeochemical cycling of nitrogen, sulphur and methane

Some hypersaline ecosystems exist in the form of halite, the salt deposits formed due to the evaporation of salt water. Over a period of time, the salt-saturated hypersaline lakes or seas get dried up, leading to the deposition of halite and other significant minerals. The ancient halite deposits may contain halophiles from the same era as the surrounding minerals. In the current study, the taxonomic diversity of halite deposited in the Drang Mine was analysed and compared with the microbiome of similar ecosystems, i.e., a nearby brine, Pangong Lake and Sambhar Lake. The analysis showed that Proteobacteria was the most abundant phylum across all the samples. The phylum Firmicutes exhibited the second-highest abundance in the Drang ecosystem, while Bacteroidetes were more numerous than Firmicutes in other selected niches. The lowest species richness based on the Chao I index was found in Sambhar Lake, likely because of the presence of two major extreme parameters, namely high salinity and alkaline pH. The species diversity calculated by Shannon and Simpson indices was lowest in Drang Mine, possibly because of the very high salt concentration in halite ecosystems, as also corroborated by physi-ochemical analysis. The beta-diversity analysis based on the Bray-Curtis matrix showed the formation of a separate cluster of Drang Mine samples, pointing towards its unique bacterial community structure as compared to other samples. The current study not only aided in the generation of baseline information about the taxonomic diversity of halite deposited in the Drang Mine but also highlighted its different bacterial community structure when compared to other similar ecosystems. It also indicated their potential role in N, S and CH4 biogeochemical cycling.