title: The Effect of Natural Organic Matter on Mercury Methylation by Desulfobulbus propionicus 1pr3.
abstract: Methylation of tracer and ambient mercury ((200)Hg and (202)Hg, respectively) equilibrated with four different natural organic matter (NOM) isolates was investigated in vivo using the Hg-methylating sulfate-reducing bacterium Desulfobulbus propionicus 1pr3. Desulfobulbus cultures grown fermentatively with environmentally representative concentrations of dissolved NOM isolates, Hg[II], and HS(-) were assayed for absolute methylmercury (MeHg) concentration and conversion of Hg(II) to MeHg relative to total unfiltered Hg(II). Results showed the (200)Hg tracer was methylated more efficiently in the presence of hydrophobic NOM isolates than in the presence of transphilic NOM, or in the absence of NOM. Different NOM isolates were associated with variable methylation efficiencies for either the (202)Hg tracer or ambient (200)Hg. One hydrophobic NOM, F1 HpoA derived from dissolved organic matter from the Florida Everglades, was equilibrated for different times with Hg tracer, which resulted in different methylation rates. A 5 day equilibration with F1 HpoA resulted in more MeHg production than either the 4 h or 30 day equilibration periods, suggesting a time dependence for NOM-enhanced Hg bioavailability for methylation.
authors.affiliation: School of Earth Sciences, University of Melbourne Melbourne, VIC, Australia.
authors.forename: John W
authors.initials: JW
authors.lastname: Moreau
authors.affiliation: School of Earth Sciences, University of Melbourne Melbourne, VIC, Australia.
authors.forename: Caitlin M
authors.initials: CM
authors.lastname: Gionfriddo
authors.affiliation: United States Geological Survey Middleton, WI, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: Krabbenhoft
authors.affiliation: United States Geological Survey Middleton, WI, USA.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Ogorek
authors.affiliation: United States Geological Survey Middleton, WI, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: DeWild
authors.affiliation: United States Geological Survey Boulder, CO, USA.
authors.forename: George R
authors.initials: GR
authors.lastname: Aiken
authors.affiliation: Department of Geology and Geophysics, University of Wisconsin-Madison Madison, WI, USA.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Roden
keywords: mercury isotopes; mercury methylation; methylmercury; natural organic matter; sulfate-reducing bacteria