Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831, USA.
Sci Total Environ. 2011 Sep 1;409(19):3943-8. doi: 10.1016/j.scitotenv.2011.06.037. Epub 2011 Jul 16.
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.
细菌生长阶段的影响是汞（Hg）甲基化的一个方面，之前的研究尚未对此进行详细研究。在这里，我们研究了生长阶段（对数中期、对数末期和静止末期）对已知甲基化菌脱硫弧菌 ND132 汞甲基化的影响。我们测试了单独添加汞（氯化物复合物）、汞与苏万尼河天然有机物（SRNOM）（未平衡）以及与 SRNOM 平衡的汞对 ND132 在丙酮酸-延胡索酸培养基中生长曲线过程中产生一甲基汞（MMHg）的影响。即使在非常低的 Hg:SRNOM 比下（预测 Hg 结合将由高能位主导），这种 NOM 也不会影响 MMHg 的产生。在采样前 24 小时（晚期添加）向生长培养物中添加 Hg 或 Hg-NOM 比向初始培养物接种时就开始暴露于 Hg 的可比龄培养物产生的净甲基汞分数高约 2 倍。对数中期和对数末期培养物产生的 MMHg 量相似，但静止末期培养物（在早期和晚期 Hg 添加条件下）产生的 MMHg 量最多增加了约 3 倍，这表明在 MMHg 产生的研究中，生长阶段具有潜在的重要性。
