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This content will become publicly available on November 14, 2017

Title: Effects of cellular sorption on mercury bioavailability and methylmercury production by Desulfovibrio desulfuricans ND132

Microbial conversion of inorganic mercury (IHg) to methylmercury (MeHg) is a significant environmental concern because of the bioaccumulation and biomagnification of toxic MeHg in the food web. Laboratory incubation studies have shown that, despite the presence of large quantities of IHg in cell cultures, MeHg biosynthesis often reaches a plateau or a maximum within hours or a day by an as yet unexplained mechanism. In this paper, we report that mercuric Hg(II) can be taken up rapidly by cells of Desulfovibrio desulfuricans ND132, but a large fraction of the Hg(II) is unavailable for methylation because of strong cellular sorption. Thiols, such as cysteine, glutathione, and penicillamine, added either simultaneously with Hg(II) or after cells have been exposed to Hg(II), effectively desorb or mobilize the bound Hg(II), leading to a substantial increase in MeHg production. The amount of thiol-desorbed Hg(II) is strongly correlated to the amount of MeHg produced (r = 0.98). Furthermore, cells do not preferentially take up Hg(II)–thiol complexes, but Hg(II)–ligand exchange between these complexes and the cell-associated proteins likely constrains Hg(II) uptake and methylation. Finally, we suggest that, aside from aqueous chemical speciation of Hg(II), binding and exchange of Hg(II) between cells and complexing ligands such as thiolsmore » and naturally dissolved organics in solution is an important controlling mechanism of Hg(II) bioavailability, which should be considered when predicting MeHg production in the environment.« less
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ; ORCiD logo [2] ;  [2] ;  [2]
  1. Chinese Academy of Sciences (CAS), Beijing (China). State Key Lab. of Urban and Regional Ecology. Research Center for Eco-Environmental Sciences; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
  3. Chinese Academy of Sciences (CAS), Beijing (China). State Key Lab. of Urban and Regional Ecology. Research Center for Eco-Environmental Sciences; Univ. of Melbourne, VIC (Australia). Dept. of Veterinary and Agricultural Sciences
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 50; Journal Issue: 24; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Contributing Orgs:
Chinese Academy of Sciences (CAS), Beijing (China); Univ. of Melbourne, VIC (Australia)
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1343527
Alternate Identifier(s):
OSTI ID: 1333760