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Environmental microbes can speciate and cycle arsenic
E Danielle Rhine1, Elizabeth Garcia-Dominguez, Craig D Phelps
1Biotechnology Center for Agriculture and the Environment, Cook College, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA.
Environmental Science & Technology
|February 16, 2006
Summary
Microorganisms can transform arsenic between arsenate and arsenite forms, influencing its environmental behavior. This redox cycling is linked to microbial metabolism and responds to changing oxygen conditions.
Area of Science:
- Environmental Microbiology
- Geochemistry
- Environmental Science
Background:
- Naturally occurring arsenic exists as arsenate [As(V)] and arsenite [As(III)]
- Arsenic contamination in groundwater poses significant health risks
- Microorganisms play a key role in mediating arsenic redox transformations
Purpose of the Study:
- To investigate microbial mediation of arsenic redox cycling
- To determine if environmental microorganisms can link arsenic redox cycling to their metabolism
- To assess the impact of dynamic environmental conditions on arsenic speciation
Main Methods:
- Isolation of an arsenate-respiring reducer (strain Y5) and an arsenite oxidizer (strain OL1) from Onondaga Lake
- Co-culturing of isolates under controlled anoxic and oxic conditions in serum bottles
- Monitoring of arsenic speciation changes over a 28-day incubation period
Main Results:
- Arsenate [As(V)] was stoichiometrically reduced to arsenite [As(III)] by microorganisms under anoxic conditions
- Arsenite [As(III)] was completely oxidized back to arsenate [As(V)] upon introduction of air (oxic conditions)
- Abiotic controls showed no significant arsenic transformation, confirming microbial mediation
Conclusions:
- Microorganisms can effectively cycle arsenic between As(V) and As(III) states
- Arsenic redox cycling is responsive to environmental oxygen availability
- Microbial arsenic cycling influences arsenic speciation, mobility, and toxicity in the environment
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