Abundance, Geo-Microbial Role and Community Diversity of Sulfate-Reducing Bacteria in Tropical Estuarine Sediments

Abstract

Sulfate-reducing bacteria (SRB), a diverse taxonomic group of anaerobic microorganisms that use oxidised sulfur compounds as terminal electron acceptors, drive the key biogeochemical process of sulfate reduction. However, little is known about the structural and functional diversity of SRB in tropical coastal habitats. Thus, the goal of this study is to explore and compare the community diversity of Ashtamudi and Vembanad estuaries and evaluate the sedimentary sulfate reduction rate. The microbiome profiling of SRB was carried out using New Generation Sequencing (NGS) techniques (Illumina sequencing) based on gene amplification of the dissimilatory sulfate reductase (dsr) enzyme to confirm the diversity and dominant taxa of SRB. The diversity of SRB represented by the alpha diversity index of the Ashtamudi estuary (6.55) was two-fold than Vembanad estuary. In the Vembanad estuary, the marine zone (4.09) harboured more diversity than the freshwater zone (1.825). High diversity and less abundant taxa in the Ashtamudi estuary point out the presence of a rare biosphere, which is hitherto unexplored. Interestingly, the diversity of SRB at the phylum level was the same in both estuaries. However, a significant difference was seen at the species level, which reveals that the difference in the community structure of SRB in both estuaries is a result of selective preponderance. This differential diversity of SRB has an obvious influence on methane production during the breakdown of organic matter in addition to sulfate reduction. Several species of SRB have an important role in the biodegradation of persistent pollutants and the removal of heavy metals.

Keywords: sulfate reduction, estuarine sediments, biogeochemistry, new generation sequencing