The origin of methyl group in methanogen- mediated mercury methylation: From the Wolfe cycle

• 成果类型: Article
• 署名作者: Gao, Jun; Yang, Jingyi; Dong, Hongzhe; Tao, Shaoyang; Shi, Jianbo; He, Bin; Bian, Xiqing; Wu, Jian-lin; Yin, Yongguang; Hu, Ligang; Jiang, Guibin
• 署名单位: Chinese Academy of Sciences; Research Center for Eco-Environmental Sciences (RCEES), CAS; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS; Chinese Academy of Sciences; University of Chinese Academy of Sciences, CAS; Macau University of Science & Technology; Jianghan University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11813
• DOI: 10.1073/pnas.2416761121
• 发表日期: 2024-10-15
• 关键词: mechanism; genome; dehydrogenase; metabolism; reduction; diversity; bacterial; coenzyme

摘要

Methylmercury (MeHg) is a bioaccumulating neurotoxin mainly produced by anaerobic microorganisms, with methanogen being one of the important methylators. A critical aspect for understanding the mechanism for microbial mercury (Hg) methylation is the origin of the methyl group. However, the origin of methyl group in methanogen- mediated Hg methylation remains unclear. This study aims to identify the source of methyl group for MeHg synthesis in methanogens. Our study revealed that Hg methylation in Methanospirillum hungatei JF-1 is closely related to methanogenesis process, according to the results of proteomic study and substrate limitation study. Next, we proved that nearly all methyl group in MeHg derives from the Wolfe cycle in this species, rather than the previously demonstrated acetyl- coenzyme A pathway, based on the results of 13 C labeling study. We then proposed the Wolfe cycle-dependent Hg methylation mechanism in this species. Further genome analyses and 13 C labeling experiments indicated that the involvement of the Wolfe cycle in Hg methylation is probably a universal feature among Hg- methylating methanogens. These findings reveal a unique Hg methylation mechanism in methanogens. Our study broadens the carbon substrates and controlling factors for MeHg synthesis in the environment, which can inform the prediction of MeHg production potential and remediation strategies for MeHg contamination.