title: Bacterial growth phase influences methylmercury production by the sulfate-reducing bacterium Desulfovibrio desulfuricans ND132.
abstract: The effect of bacterial growth phase is an aspect of mercury (Hg) methylation that previous studies have not investigated in detail. Here we consider the effect of growth phase (mid-log, late-log and late stationary phase) on Hg methylation by the known methylator Desulfovibrio desulfuricans ND132. We tested the addition of Hg alone (chloride-complex), Hg with Suwannee River natural organic matter (SRNOM) (unequilibrated), and Hg equilibrated with SRNOM on monomethylmercury (MMHg) production by ND132 over a growth curve in pyruvate-fumarate media. This NOM did not affect MMHg production even under very low Hg:SRNOM ratios, where Hg binding is predicted to be dominated by high energy sites. Adding Hg or Hg-NOM to growing cultures 24 h before sampling (late addition) resulted in ~2× greater net fraction of Hg methylated than for comparably aged cultures exposed to Hg from the initial culture inoculation (early addition). Mid- and late-log phase cultures produced similar amounts of MMHg, but late stationary phase cultures (both under early and late Hg addition conditions) produced up to ~3× more MMHg, indicating the potential importance of growth phase in studies of MMHg production.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831, USA.
authors.forename: Abir
authors.initials: A
authors.lastname: Biswas
authors.forename: Scott C
authors.initials: SC
authors.lastname: Brooks
authors.forename: Carrie L
authors.initials: CL
authors.lastname: Miller
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Mosher
authors.forename: Xiangping L
authors.initials: XL
authors.lastname: Yin
authors.forename: Meghan M
authors.initials: MM
authors.lastname: Drake
mesh_terms: D045285:Desulfovibrio desulfuricans / Q000254:growth & development / Q000378:metabolism*; D020387:Food Chain; D008745:Methylation; D008767:Methylmercury Compounds / Q000378:metabolism*; D045483:Rivers / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical