Cysteine Inhibits Mercury Methylation by Geobacter sulfurreducens PCA Mutant Δ omcBESTZ
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
For cysteine enhances Hg uptake and methylation by Geobacter sulfurreducens PCA wild type (WT) strain in short-term assays. The prevalence of this enhancement in other strains remains poorly understood. We examined the influence of cysteine concentration on time-dependent Hg(II) reduction, sorption and methylation by PCA-WT and its c-type cytochrome-deficient mutant ( omcBESTZ) in phosphate buffered saline. Without cysteine, the mutant methylated twice as much Hg(II) as the PCA-WT, whereas addition of cysteine inhibited Hg methylation, regardless of the reaction time. PCA-WT, but, exhibited both time-dependent and cysteine concentration-dependent methylation. In 144 hour assay, nearly complete sorption of the Hg(II) by PCA-WT occurred in the presence of 1 mM cysteine, resulting in our highest observed methylmercury production. Moreover, the chemical speciation modeling and experimental data suggest that uncharged Hg(II) species are more readily taken up, and that this uptake is kinetic limiting, thereby affecting Hg methylation by both mutant and WT.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER); USDOE Office of Science (SC), Nuclear Physics (NP)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1185991
- Journal Information:
- Environmental Science & Technology Letters (Online), Vol. 2, Issue 5; ISSN 2328-8930
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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