Abstract
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 AsV-reducing bacteria (Arthrobacter sp. QXT-31 and Sphingopyxis sp. QXT-31) in a culture medium containing initial AsV (10μM) and bivalent manganese (MnII, 175μM), we demonstrated how the interactions between strains affect valence state and partition of As. The results showed that both the strains first reduced AsV to AsIII via a detoxification mechanism during aerobic growth, with participation of AsV-reducing gene arsC; the expression of a MnII-oxidizing gene of Arthrobacter sp. QXT-31 was then triggered in the presence of Sphingopyxis sp. QXT-31, and emerging MnII-oxidizing activity oxidized 90% of MnII to Mn oxides; the formed Mn oxides oxidized AsIII to AsV and adsorbed AsV; MnII-oxidizing activity decreased significantly in the later stage, resulting to desorption of AsV 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.
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