Bacterial Dynamics in the Northern Indian Ocean Region: Understanding from the Pre-genomics to Present-Day OMICS Era

Abstract

The Northern Indian Ocean (NIO) is one of the most characteristic regions of the world oceans with diverse oceanographic features. Understanding of the microbial community structure in these unique habitats has rapidly increased in the last decade, especially with the advent of molecular tools and the application of NGS technologies. Studies on marine microbial ecology in the NIO regions, from the pre-genomics era relied on culture techniques, microscopic observations, qualitative plate assays and biochemical tests. Molecular techniques and 16S rRNA gene sequencing introduced after the late 1990s significantly enhanced the understanding of bacterial diversity. These molecular tools revealed the presence of bacterial phyla and provided insights into their functional characteristics. Recent, NGS-based metagenomic studies further expanded the understanding of bacterial community structures, especially in the oxygen minimum zones and deep-sea sediments. These tools have identified bacterial taxa in-depth, revealing the existence of numerous Candidatus taxa known only by their genomic makeup. Despite these advancements, a large part of the bacterial diversity from the NIO remains unexplored, with many unanswered questions related to microbial carbon pump. Further transcriptome based studies can greatly improve the understanding of the microbial processes in the NIO, which is a dynamic, oceanographic habitat.