In addition to be naturally present in bedrock aquifers, arsenic from anthropogenic activities also accumulate in low concentrations in aquatic environments. Arsenite (As(III)) and arsenate (As(V)) represent the two most common oxidation states of arsenic in aquatic environments. As(III) is less particle reactive and represents the more hydrologically mobile form of arsenic, whereas As(V) readily adsorbs to mineral surfaces and is less mobile. As the abiotic reduction of As(V) is slow, As(V) is considered to be mainly reduced microbially via respiration or detoxification processes. In this study, the impact of low concentrations of arsenic on the anaerobic respiration of manganese and iron oxy(hydr)oxides by a model metal-reducing microorganism was investigated. Results reveal that exposure to relatively low As(V) concentrations activates respiration of iron and manganese by both <i>Shewanella putrefaciens</i> strain 200 and <i>S. oneidensis</i> strain MR-1 when phosphate availability is low only. Above a certain As(V) threshold, however, the toxicity of As(V) appears irreversible and rates of both manganese and iron reduction decrease significantly. Arsenic speciation measurements during these experiments demonstrate that the toxicity of arsenic is regulated by the complex interplay between surface reactions and redox processes. Overall, these findings suggest that phosphate transporters may be involved in the uptake of As(V) from the environment and that As(V) toxicity promotes reductive dissolution of two important contaminant scavengers in natural environments.

Impact of arsenic on microbial metal reduction

2019 Spring National Meeting

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