Phylogenetic diversity of culturable marine bacteria from sediments underlying the oxygen minimum zone of the Arabian Sea and their role in nitrate reduction

Abstract

The eastern Arabian Sea has a unique and permanent oxygen minimum zone (OMZ) extending along the western continental margin of India. The Arabian Sea OMZ is a site of intense denitrification, contributing to 20% of the global oceanic denitrification, playing a significant role in the nitrogen cycle. This study reveals the members of the culturable marine bacterial communities thriving and functioning in the sediment underlying the Arabian Sea OMZ, through 16S rDNA phylogenetic analysis and elucidating their nitrate reduction potential. Phylogenetic analyses revealed that these cultured bacteria distributed into five phyla, viz. Firmicutes (45.7%) Gammaproteobacteria (36.84%), Actinobacteria (8.7%), Bacteroidetes (5.26%), and Alphaproteobacteria (3.5%). The presence of denitrification genes such as narG, nirS, and nosZ in the cultured bacteria (39%) explains their importance in this process. Present study on the diversity and distribution of bacterial communities in the OMZ surface sediment and their probable role in the nitrogen cycle will provide insight into the microbial biogeochemical processes occurring in this region