Microbial profiling of the Himalayan Puga geothermal system

Terrestrial hot springs are emerging as leading candidate sites for the origin of life based on biotically favorable combinations of geophysicochemical properties. Within the diverse scope of hot springs observed globally the Puga geothermal system of the Indian Himalayas offers a unique perspective due an enrichment with Boron, an element associated with early Earth hot spring deposits and prebiotic chemistry. To provide insight into the biology of the Puga hot springs and contribute to an astrobiological understanding, we profiled the microbial communities of ten microsites across four active springs. Overall, a low species richness and diversity was observed, consistent with extreme environments. The most highly abundant phyla included Proteobacteria (26.8%), Bacteroidetes (14.1%), Chloroflexi (12.6%), Aquificae (11.0%) and Cyanobacteria (8.4%). Most of the identified bacteria are known thermophiles with many members renowned geothermal inhabitants. However, Archaea were not detected within our data. Variation in the relative abundance of taxa resulted in distinct microbial profiles for each of the microsites. Significant intra- and inter-spring variations suggest biogeographical factors to be effective at site level, and biogeochemical factors at microsite scale. Sub-sinter niches present as potential microsites for the origin of life and may be among the most fruitful for modelling of abiogenesis. Our work highlights the microbial complexity of the Puga hot springs and raises the importance of considering microsite variation across hot springs in general.