Effects of electron transfer mediators on the bioreduction of lepidocrocite ({gamma}-FeOOH).
Electron transfer mediators (ETMs) such as low-molecular-mass quinones (e.g., juglone and lawsone) and humic substances are believed to play a role in many redox reactions involved in contaminant transformations and the biogeochemical cycling of many redox-active elements (e.g., Fe and Mn) in aquatic and terrestrial environments. This study examines the effects of a series of compounds representing major classes of natural and synthetic organic ETMs, including low-molecular-mass quinones, humic substances, phenazines, phenoxazines, phenothiazines, and indigo derivatives, on the bioreduction of lepidocrocite ({gamma}-FeOOH) by the dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens CN32. Although S. putrefaciens CN32 was able to reduce lepidocrocite in the absence of exogenous ETMs, the addition of exogenous ETMs enhanced the bioreduction of lepidocrocite. In general, the rate of Fe(II) production correlated well with the reduction potentials of the ETMs. The addition of humic acids or unfractionated natural organic matter at concentrations of 10 mg organic C L{sup -1} resulted in, at best, a minimal enhancement of lepidocrocite bioreduction. This observation suggests that electron shuttling by humic substances is not likely to play a major role in Fe(III) bioreduction in oligotrophic environments such as subsurface sediments with low organic C contents.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); USDOD
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 973020
- Report Number(s):
- ANL/BIO/JA-61104; ESTHAG; TRN: US201005%%509
- Journal Information:
- Environ. Sci. Technol., Vol. 42, Issue 18 ; Aug. 20, 2008; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- ENGLISH
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