Metagenomic insights into production of zero valent sulfur from dissimilatory sulfate reduction in a methanogenic bioreactor

Abstract

Dissimilatory sulfate reduction mediated by sulfate-reducing microorganisms (SRMs) has a pivotal role in the sulfur cycle, from which the generation of zero valent sulfur (ZVS) represents a novel pathway. Molecular details in the sulfite reduction to sulfide are still in debate. Also, the community composition and metabolic potential in sulfate-to-ZVS microbial communities remain to be elucidated. In this study, we employed genome-centric metagenomics approach to investigate the major players in a sulfate-to-ZVS bioreactor (ZVS-SR). Totally 51 metagenome assembled genomes (MAGs) were retrieved from the ZVS-SR microbiome, most belonging to phyla Proteobacteria, Actinobacteria, Bacteroides and Chloroflexi. Major players possibly responsible for ZVS generation included Desulfobacter, Desulfococcus, Desulfobacula and Desulfobacterales. A Desulfobacterales bacterium (SRB-bin23) was selected for subsequent detailed characterization of genome-encoded metabolic pathways and key functional genes involved in ZVS generation. This study expands our knowledge on the dissimilatory sulfate reduction in SRMs and may have important environmental implications.