Exploring the culturable bacterial diversity and its hydrocarbon degrading potentiality isolated from the Oxygen Minimum Zone Sediments of Bay of Bengal

Understanding biota distribution in oxygen minimum zone can help guide further exploration of potentially unusual habitats. The present study explores the culturable bacterial fractions in the oxygen minimum zone sediments of Bay of Bengal. The 16S rRNA gene sequences of 30 morphologically distinct bacterial colonies isolated form oxygen minimum zone of Bay of Bengal reveals 25 phylo-types, predominated by Proteobacteria (83.3%) and Actinobacteria (16.6%). Over all, Alphaproteobacteria and Gammaproteobacteria dominated the culturable fraction in this study. The overall pair-wise distances of bacterial isolates of Bay of Bengal is two times lesser when compared to overall pair-wise distance of bacterial isolates from oxygen minimum zone of Arabian Sea indicating relatively low genetic distances in Bay of Bengal. Not even 1% of bacterial cells in oxygen minimum zone of Bay of Bengal are culturable. We found that oxygen concentration alone could not be a deciding factor of culturable bacterial diversity in oxygen minimum zone. More than 50% bacterial isolates of present study is an active degraders of hydrocarbons. Higher similarity of 16S rRNA sequences produced in this study with that of previously reported efficient hydrobonoclastic bacterial isolates like Vibrio diazotrophicus, Vibrio cyclotrophicus, Pseudomonas poae, Marinobacter hydrocarbonoclasticus, Marinobacter flavimaris and Alcanivorax borkumensis further strengthens the evidence of hydrocarbon presence in Bay of Bengal sediments. This study is first of its time addresses the diversity of culturable bacterial fractions in oxygen minimum zone sediments of Bay of Bengal. Higher number of bacterial isolates from oxygen minimum zone of Bay of Bengal has carbonoclastic potentialities implying that they may play an important role in in situ hydrocarbon degradation in oxygen minimum zone of Bay of Bengal.