Microbial distribution and diversity along a vertical profile in the water column of a seasonal Oxygen minimum zone in the Southeast Arabian Sea

Abstract

The Oxygen Minimum Zones (OMZ) support a milieu of microbial communities capable of degrading complex molecules. The current study reports the vertical distribution of microorganisms and diversity of bacteria in Arabian Sea OMZ, measured using fluorescence in situ hybridization (FISH) technique and 16S rRNA gene amplicon sequencing respectively. Bacterial and archaeal abundances were of the magnitude 104–105 and 103 cells ml−1 respectively. Proteobacteria was the most abundant phyla. The other phyla included were Bacteriodota, Actinobacteria, Verrucomicrobia, Marinimicrobia, Chloroflexi, Nitrospinota and SAR 324 clade. The results of alpha diversity analysis (Shannon and Chao1) of OTUs showed that the bacterial communities were different between physically close water masses at different depths in an OMZ. The predictive analysis of metagenome functions showed that the bacteria present in OMZ were able to metabolize different complex molecules such as polysaccharides, aromatic compounds, nucleosides, sulfur under hypoxic conditions in the OMZ. Overall, the results of the current study indicate the OMZ is a niche for a diverse group of bacteria which can process various complex metabolites. Further studies on the isolation and functional characterization of these microorganisms may be beneficial for exploring their biotechnological potentials.