Biodegradation of sodium selenite by a highly tolerant strain Rhodococcus qingshengii PM1: Biochemical characterization and comparative genome analysis

Background

Rhodococcus is an important genus of soil bacteria known for its metabolic diversity and environmental adaptability under harsh and contaminated conditions. However, few studies have reported on the selenium metabolism of Rhodococcus species.

Results

Here, we isolated a highly selenite-resistance strain PM1 (up to 100 mM) from a selenium-rich mine in Enshi City. This strain reduced 50 mM sodium selenite by 99 % within 72 h. SEM and XPS revealed that PM1 reduced selenite to selenium nanorods (SeNRs). Phylogenetic analysis identified PM1 as R. qingshengii. The whole genome of strain PM1 was sequenced, and a comparative genome analysis of strain PM1with 64 other genomes of Rhodococcus was performed. Whole genome sequencing identified a total of 97 heavy metal resistance genes in strain PM1. Comparative genomics revealed that Rhodococcus species possess an open pan-genome, indicating adaptability to diverse environments. Genomic analysis revealed a total of 96 putative selenite-reducing proteins in strain PM1. Four gene clusters, involved in the pentose phosphate pathway, iron-sulfur cluster assembly, sulfate reductase cluster, and sulfate transport complex, showed high conservation of sequence identity within these species.

Conclusions

To our knowledge, this research enhances our understanding of high selenite reduction in strain PM1 at genomic level and elucidates the biotechnological applications of selenite-reducing bacteria in environmental remediation.