Barrouilhet Sophie, Monperrus Mathilde, Tessier Emmanuel, Khalfaoui-Hassani Bahia, Guyoneaud Rémy, Isaure Marie-Pierre, Goñi-Urriza Marisol
Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Pau, France.
Universite de Pau Et Des Pays de L'Adour, E2S UPPA, CNRS, IPREM UMR 5254, Anglet, France.
Environ Sci Pollut Res Int. 2023 Jan;30(2):3835-3846. doi: 10.1007/s11356-022-22173-y. Epub 2022 Aug 12.
Mercury (Hg) is a global pollutant of environmental and health concern; its methylated form, methylmercury (MeHg), is a potent neurotoxin. Sulfur-containing molecules play a role in MeHg production by microorganisms. While sulfides are considered to limit Hg methylation, sulfate and cysteine were shown to favor this process. However, these two forms can be endogenously converted by microorganisms into sulfide. Here, we explore the effect of sulfide (produced by the cell or supplied exogenously) on Hg methylation. For this purpose, Pseudodesulfovibrio hydrargyri BerOc1 was cultivated in non-sulfidogenic conditions with addition of cysteine and sulfide as well as in sulfidogenic conditions. We report that Hg methylation depends on sulfide concentration in the culture and the sulfides produced by cysteine degradation or sulfate reduction could affect the Hg methylation pattern. Hg methylation was independent of hgcA expression. Interestingly, MeHg production was maximal at 0.1-0.5 mM of sulfides. Besides, a strong positive correlation between MeHg in the extracellular medium and the increase of sulfide concentrations was observed, suggesting a facilitated MeHg export with sulfide and/or higher desorption from the cell. We suggest that sulfides (exogenous or endogenous) play a key role in controlling mercury methylation and should be considered when investigating the impact of Hg in natural environments.
汞（Hg）是一种引发环境和健康问题的全球性污染物；其甲基化形式甲基汞（MeHg）是一种强效神经毒素。含硫分子在微生物产生甲基汞的过程中发挥作用。虽然硫化物被认为会限制汞的甲基化，但已表明硫酸盐和半胱氨酸有利于这一过程。然而，这两种形式可被微生物内源性地转化为硫化物。在此，我们探究了（细胞产生的或外源供应的）硫化物对汞甲基化的影响。为此，在非产硫化物条件下添加半胱氨酸和硫化物培养了汞还原脱硫弧菌（Pseudodesulfovibrio hydrargyri）BerOc1，同时也在产硫化物条件下进行了培养。我们报告称，汞的甲基化取决于培养物中的硫化物浓度，并且半胱氨酸降解或硫酸盐还原产生的硫化物会影响汞的甲基化模式。汞的甲基化与hgcA表达无关。有趣的是，甲基汞的产生在硫化物浓度为0.1 - 0.5 mM时达到最大值。此外，观察到细胞外培养基中的甲基汞与硫化物浓度的增加之间存在很强的正相关，这表明甲基汞随着硫化物更容易从细胞中输出和/或从细胞上更高程度地解吸。我们认为，硫化物（外源的或内源的）在控制汞的甲基化方面起着关键作用，并且在研究汞在自然环境中的影响时应予以考虑。
