Comparative metagenomic analyses of a high-altitude Himalayan geothermal spring revealed temperature-constrained habitat-specific microbial community and metabolic dynamics.

Abstract

Metagenomic surveys across microbial mat (~ 55°C) samples of high-altitude (1760m above sea level) Himalayan geothermal springs have revealed specialized community enriched with niche-specific functions. In this study, we have performed metagenomic sequence-based analyses to get insights into taxonomic composition and functional potential of hyperthermophiles in water (~ 95°C) and sediment samples (78-98°C). Community analyses revealed predominance of thermophilic bacterial and archeal genera dwelling in water in contrast to microbial mats (55°C), namely Methylophilus, Methyloversatilis, Emticicia, Caulobacter, Thermus, Enhydrobacter and Pyrobaculum. Sediment samples having surface temperature (~ 78°C) were colonized by Pyrobaculum and Chloroflexus while genus Massilia was found to be inhabited in high-temperature sediments (~ 98°C). Functional analyses of metagenomic sequences revealed genetic enrichment of genes such as type IV secretion system, flagellar assembly and two-component system in contrast to mats. Furthermore, inter-sample comparison of enriched microbial diversity among water, sediment and microbial mats revealed habitat-specific clustering of the samples within same environment highlighting the role of temperature dynamics in modulating community structure across different habitats in same niche. However, function-based analysis demonstrated site-specific clustering among sediment, microbial mat and water samples. Furthermore, a novel thermophilic genotype of the genus Emticicia (designated as strain MM) was reconstructed from metagenome data. This is a correlative study between three major habitats present in geothermal spring environment, i.e., water, sediment and microbial mats revealing greater phylogenetic and functional dispersion emphasizing changing habitat-specific dynamics with temperature.