Microbial Interspecies Interactions Affect Arsenic Fate in the Presence of Mn^II

Biotransformation of arsenic (As) plays an important role in its environmental fate. However, the impact of direct microbial interspecies interactions on valence state and migration of As is rarely reported and cognized. Here, by co-cultivating two aerobic As^V-reducing bacteria (Arthrobacter sp. QXT-31 and Sphingopyxis sp. QXT-31) in a culture medium containing initial As^V (10 μM) and bivalent manganese (Mn^II, 175 μM), we demonstrated how the interactions between strains affect valence state and partition of As. The results showed that both the strains first reduced As^V to As^III via a detoxification mechanism during aerobic growth, with participation of As^V-reducing gene arsC; the expression of a Mn^II-oxidizing gene of Arthrobacter sp. QXT-31 was then triggered in the presence of Sphingopyxis sp. QXT-31, and emerging Mn^II-oxidizing activity oxidized 90% of Mn^II to Mn oxides; the formed Mn oxides oxidized As^III to As^V and adsorbed As^V; Mn^II-oxidizing activity decreased significantly in the later stage, resulting to desorption of As^V from Mn oxides and subsequent bioreduction in aqueous phase. Considering the universality of the two bacterial genera and the interspecies interactions, our study hints at the pervasive impact of direct microbial interspecies interactions on the environmental fate of As in an aquatic ecosystem containing Mn.