Genomic Insights into the Bioremediation Potential and Codon Usage Dynamics of a Multi-Metal Resistant Bacillus tropicus Strain from Forest Soil

Heavy metals and metalloids are increasingly dispersed throughout different parts of the planet due to various human activities, leading to toxicity in living organisms. Bacterial cells have tremendous potential to bioaccumulate or degrade enzymatically toxic heavy metals and adsorb metal ions. This study was done to evaluate the growth kinetics, bioaccumulation and biosorption potential, metabolic profile, and chromate reductase activity of an indigenous forest soil bacterium, Bacillus tropicus RWS2. The bacterium was able to bioaccumulate 47.6 mg g−1 of Pb, 56.9 mg g−1 of Cr, and 37.8 mg g−1 of As(V) with a removal efficiency of 97.5%, 74.2% and 44.94%, respectively. The Pb and Cr biosorption potential of the dried cellular biomass of the bacterium was relatively high. The bacterium also depicted potential in reducing the toxic hexavalent chromate to the trivalent form. Whole genome sequencing and codon usage analysis were also performed. The bacterial genome was found to comprise about 23 genes associated with heavy metal tolerance. Codon usage bias analysis depicted a moderately biased genome, while natural selection was predominant in shaping the codon usage bias of the genes associated with conferring heavy metal resistance to multiple heavy metals. This study demonstrates RWS2 as a multi-metal resistant bacterium and the combined physiological, biochemical, and genomic features of RWS2 underscore its promise as a genetically adaptable and efficient bioremediation agent.