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THE INFLUENCE OF SULFIDE ON MERCURY BIOAVAILABILITY FOR METHYLATION BY PURE CULTURES OF DESULFOBULBUS PROPRIONICUS. (R827653)
Citation:
Benoit, J. M., C. C. Gilmour, AND R. P. Mason. THE INFLUENCE OF SULFIDE ON MERCURY BIOAVAILABILITY FOR METHYLATION BY PURE CULTURES OF DESULFOBULBUS PROPRIONICUS. (R827653). ENVIRONMENTAL SCIENCE & TECHNOLOGY. International Biometric Society.
Description:
To help understand the mechanism and control of Hg
uptake in Hg-methylating bacteria, we investigated the effect
of sulfide on Hg methylation by pure cultures of the sulfate-reducing bacterium Desulfobulbus propionicus (1pr3).
Our previous research in natural sediments has suggested
that Hg methylation occurs most rapidly when sulfide
concentrations favor formation of neutral dissolved Hg-S
species. In this study, the chemical speciation of Hg in
culture media was manipulated by growing D. propionicus
across a range of sulfide concentrations, with inorganic
Hg (HgI) added in the form of ground ores. A solid-phase,
rather than a dissolved source of Hg, was used to
simulate the controls on Hg partitioning between solid
and aqueous phases found in natural sediments. Methylmercury (MeHg) production by cultures was not related
to the absolute solid-phase concentration of Hg in the ores,
and it was only weakly related to the dissolved HgI
concentration in the medium. However, MeHg production
was linearly related to the calculated concentration of
the dominant neutral complex in solution, HgS
. Furthermore,
the diffusive membrane permeability of HgS, as estimated
from its octanol-water partitioning coefficient, was
found to be sufficient to support MeHg production by
cells. The present paper expands on our previous work
by providing experimental support of our hypothesis that
sulfide influences methylation by affecting the speciation of
dissolved HgI and its uptake via passive diffusion.