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Flexible bacterial strains that oxidize arsenite in anoxic or aerobic conditions and utilize hydrogen or acetate as alternative electron donors

Lookup NU author(s): Dr Lucia Rodriguez Freire


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Arsenic is a carcinogenic compound widely distributed in the groundwater around the world. The fate of arsenic in groundwater depends on the activity of microorganisms either by oxidizing arsenite (AsIII), or by reducing arsenate (AsV). Because of the higher toxicity and mobility of AsIII compared to AsV, microbial-catalyzed oxidation of AsIII to AsV can lower the environmental impact of arsenic. Although aerobic AsIII-oxidizing bacteria are well known, anoxic oxidation of AsIII with nitrate as electron acceptor has also been shown to occur. In this study, three AsIII-oxidizing bacterial strains, Azoarcus sp. strain EC1-pb1, Azoarcus sp. strain EC3-pb1 and Diaphorobacter sp. strain MC-pb1, have been characterized. Each strain was tested for its ability to oxidize AsIII with four different electron acceptors, nitrate, nitrite, chlorate and oxygen. Complete AsIII oxidation was achieved with both nitrate and oxygen, demonstrating the novel ability of these bacterial strains to oxidize AsIII in either anoxic or aerobic conditions. Nitrate was only reduced to nitrite. Different electron donors were used to study their suitability in supporting nitrate reduction. Hydrogen and acetate were readily utilized by all the cultures. The flexibility of these AsIII-oxidizing bacteria to use oxygen and nitrate to oxidize AsIII as well as organic and inorganic substrates as alternative electron donors explains their presence in non-arsenic-contaminated environments. The findings suggest that at least some AsIII-oxidizing bacteria are flexible with respect to electron-acceptors and electron-donors and that they are potentially widespread in low arsenic concentration environments.

Publication metadata

Author(s): Rodriguez-Freire L, Sun W, Sierra-Alvarez R, Field JA

Publication type: Article

Publication status: Published

Journal: Biodegradation

Year: 2012

Volume: 23

Pages: 133-143

Print publication date: 01/02/2012

Online publication date: 26/06/2011

ISSN (print): 0923-9820

ISSN (electronic): 1572-9729

Publisher: Springer


DOI: 10.1007/s10532-011-9493-x


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