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

Lucía Rodríguez-Freire, Wenjie Sun, Reyes Sierra-Alvarez, Jim A. Field

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


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 (As III), or by reducing arsenate (As V). Because of the higher toxicity and mobility of As III compared to As V, microbial-catalyzed oxidation of As III to As V can lower the environmental impact of arsenic. Although aerobic As III-oxidizing bacteria are well known, anoxic oxidation of As III with nitrate as electron acceptor has also been shown to occur. In this study, three As III-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 As III with four different electron acceptors, nitrate, nitrite, chlorate and oxygen. Complete As III oxidation was achieved with both nitrate and oxygen, demonstrating the novel ability of these bacterial strains to oxidize As III 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 As III-oxidizing bacteria to use oxygen and nitrate to oxidize As III 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 As III-oxidizing bacteria are flexible with respect to electron-acceptors and electron-donors and that they are potentially widespread in low arsenic concentration environments.

Original languageEnglish (US)
Pages (from-to)133-143
Number of pages11
Issue number1
StatePublished - Feb 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Pollution
  • Bioengineering
  • Environmental Engineering
  • Microbiology
  • Environmental Chemistry


  • Arsenite oxidation
  • Flexibility
  • Metabolism
  • Nitrate reduction
  • Pure culture


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