Complex bacterial communities in the deep-sea sediments of the Bay of Bengal and volcanic Barren Island in the Andaman Sea

Abstract

Deep-sea environments are gaining global attention as potential sources of useful microorganisms, thereby warranting a better understanding of the diversity and genomic potential of the microbes present. To this end, here we provide the first insights into the composition of the bacterial communities in deep-sea sediment samples from the southwestern Bay of Bengal and the geographically distinct volcanic Barren Island in the Andaman Sea. High-throughput 16S rRNA gene sequencing of the sediments revealed the presence of >44,000 operational taxonomic units (OTUs) in each of the samples, suggesting high bacterial diversity. Actinobacteria was the most dominant phylum, representing >20% of the taxonomically assignable OTUs, followed by Firmicutes, Proteobacteria, and Chloroflexi. Numerous bacteria that are potentially involved in the sulfur cycle were observed in the Barren Island sediment sample, while bacteria with clinical and industrial potential were observed in the samples from the southwestern Bay of Bengal. Correlation analysis of the biotic and abiotic parameters showed that the differences in bacterial richness and community composition between the sampling sites were mainly dependent on sediment texture. Using a predictive functional metagenomic approach, this study also discusses the genetic variations that may provide an adaptive advantage to sediment bacterial communities for survival in these extreme deep-sea environments. The results from this study should aid future studies focused on bioprospecting and geochemical cycling in the deep sea.