Abstract
Selenium (Se), a potentially toxic trace element, undergoes complex biogeochemical cycling in the environment, largely driven by microbial activity. The reduction in selenate or selenite to elemental selenium is an environmentally beneficial process, as it decreases both Se toxicity and mobility. This reduction is catalyzed by enzymes encoded by various related genes. The link between Se reduction gene clusters and specific taxonomic groups is significant for elucidating the ecological roles and processes of Se reduction in diverse environments. In this study, a new species of Se-reducing microorganism belonging to the genus Anaerobacillus was isolated from a mining site. A comparative analysis of the growth characteristics reveals that Anaerobacillus species exhibit notable metabolic versatility, particularly in their fermentation abilities and utilization of diverse electron donors and acceptors. Genome analysis identified a diverse array of gene clusters associated with selenate uptake (sul, pst), selenate reduction (ser), and selenite reduction (hig, frd, trx, and bsh). Since selenate reduction is the first crucial step in Se reduction, genes linked to selenate reductase are the focus. The serA gene clusters analysis suggests that the serA gene is highly conserved across Anaerobacillus species. The surrounding genes of serA show significant variability in both presence and gene size. This evolutionary difference in coenzyme utilization and serA regulation suggests distinct survival strategies among Anaerobacillus species. This study offers insights into Se bio-transformations and the adaptive strategies of Se-reducing microorganisms.