Phylogenetic and genome analyses of antimony-oxidizing bacteria isolated from antimony mined soil

Antimony-oxidizing bacteria play an important role in the biogeochemical cycling of antimony, converting the more toxic Sb(Ⅲ) to the less toxic Sb(Ⅴ). Little is known about the bacterial species and mechanisms involved in mediating Sb(Ⅲ) oxidation. In this study, 25 Sb(Ⅲ)-resistant bacteria were isolated from Sb mined soil. Among these strains, 6 were Sb(Ⅲ)-oxidizing bacteria including Acinetobacter sp. JL7, Comamonas sp. JL25, Comamonas sp. JL40, Comamonas sp. S44, Stenotrophomonas sp. JL9 and Variovorax sp. JL23. Strain S44 showed the highest Sb(Ⅲ) oxidation rate which could aerobically oxidize 50 μM Sb(Ⅲ) to Sb(Ⅴ) in 3 d. Whole genome sequencing of strain S44 revealed a number of genes encoding putative metal(loid) resistance proteins including 2 putative As(Ⅲ)/Sb(Ⅲ) efflux pump proteins ArsB. Based on our study, the ability of Sb(Ⅲ) resistance and oxidation was found among diverse bacterial lineages. Microbiological oxidation of Sb(Ⅲ) may therefore be widely distributed across different bacterial lineages mediating detoxification of Sb at high concentrations in the environment.