Department of Biochemistry and Microbiology, Rutgers, the State University of New Jersey, New Brunswick, New Jersey, USA.
School of Marine Science and Policy, University of Delaware, Newark, Delaware, USA.
mBio. 2019 Apr 2;10(2):e00183-19. doi: 10.1128/mBio.00183-19.
Mercury (Hg) is a widely distributed, toxic heavy metal with no known cellular role. Mercury toxicity has been linked to the production of reactive oxygen species (ROS), but Hg does not directly perform redox chemistry with oxygen. How exposure to the ionic form, Hg(II), generates ROS is unknown. Exposure of to Hg(II) triggered ROS accumulation and increased transcription and activity of superoxide dismutase (Sod) and pseudocatalase (Pcat); however, Hg(II) inactivated Sod and Pcat. Strains lacking Sod or Pcat had increased oxidized bacillithiol (BSH) levels and were more sensitive to Hg(II) than the wild type. The Δ Δ and Δ Δ double mutant strains were as sensitive to Hg(II) as the Δ strain that lacks bacillithiol, suggesting that the increased sensitivity to Hg(II) in the Δ and Δ mutant strains is due to a decrease of reduced BSH. Treatment of with Hg(II) decreased aconitase activity and increased the intracellular concentration of free Fe, and these phenotypes were exacerbated in Δ and Δ mutant strains. Treatment with Hg(II) also increased DNA damage. We conclude that sequestration of the redox buffering thiol BSH by Hg(II), in conjunction with direct inactivation of ROS-scavenging enzymes, impairs the ability of to effectively metabolize ROS generated as a normal consequence of growth in aerobic environments. is a deep-branching thermophilic aerobe. It is a member of the - phylum that, together with the , constitute the earliest branching aerobic bacterial lineages; therefore, this organism serves as a model for early diverged bacteria (R. K. Hartmann, J. Wolters, B. Kröger, S. Schultze, et al., Syst Appl Microbiol 11:243-249, 1989, https://doi.org/10.1016/S0723-2020(89)80020-7) whose natural heated habitat may contain mercury of geological origins (G. G. Geesey, T. Barkay, and S. King, Sci Total Environ 569-570:321-331, 2016, https://doi.org/10.1016/j.scitotenv.2016.06.080). likely arose shortly after the oxidation of the biosphere 2.4 billion years ago. Studying physiology provides clues about the origin and evolution of mechanisms for mercury and oxidative stress responses, the latter being critical for the survival and function of all extant aerobes.
汞（Hg）是一种广泛分布的有毒重金属，在细胞中没有已知的作用。汞毒性与活性氧物质（ROS）的产生有关，但 Hg 并不直接与氧气进行氧化还原化学作用。暴露于离子形式的 Hg(II) 如何产生 ROS 尚不清楚。暴露于 Hg(II) 会触发 ROS 积累，并增加超氧化物歧化酶（Sod）和假过氧化氢酶（Pcat）的转录和活性；然而，Hg(II) 使 Sod 和 Pcat 失活。缺乏 Sod 或 Pcat 的菌株具有更高的氧化杆菌硫醇（BSH）水平，并且比野生型菌株对 Hg(II) 更敏感。ΔΔ和ΔΔ双突变菌株与缺乏杆菌硫醇的Δ菌株一样对 Hg(II)敏感，这表明 Δ和Δ突变菌株对 Hg(II)的敏感性增加是由于还原型 BSH 的减少。用 Hg(II)处理会降低乌头酸酶的活性并增加细胞内游离铁的浓度，并且这些表型在 ΔΔ突变菌株中加剧。用 Hg(II)处理也会增加 DNA 损伤。我们得出结论，Hg(II)对氧化还原缓冲硫醇 BSH 的螯合，加上对 ROS 清除酶的直接失活，削弱了细菌有效代谢有氧环境中生长所产生的 ROS 的能力。是一种深分支的嗜热好氧菌。它是-门的成员，与-门一起构成最早分支的好氧细菌谱系；因此，该生物体是早期分化细菌的模型（R. K. Hartmann、J. Wolters、B. Kröger、S. Schultze 等人，系统应用微生物学 11:243-249，1989 年，https://doi.org/10.1016/S0723-2020(89)80020-7）其天然热栖息地可能含有地质起源的汞（G. G. Geesey、T. Barkay 和 S. King，《全面环境科学》569-570:321-331，2016 年，https://doi.org/10.1016/j.scitotenv.2016.06.080）。它可能在 24 亿年前生物圈氧化后不久就出现了。研究生理学为汞和氧化应激反应机制的起源和进化提供了线索，后者对于所有现存好氧生物的生存和功能至关重要。
