Department of Microbiology, IWWR, Faculty of Science, Radboud University, Nijmegen, the Netherlands.
Molecular Bioenergetics Group, Radboud Institute for Molecular Life Sciences, Department of Pediatrics, Radboud University Medical Center, Geert-Grooteplein Zuid 10, 6525 GA Nijmegen, the Netherlands.
Biochim Biophys Acta Bioenerg. 2019 Sep 1;1860(9):734-744. doi: 10.1016/j.bbabio.2019.07.011. Epub 2019 Jul 31.
The atmospheric concentration of the potent greenhouse gases methane and nitrous oxide (NO) has increased drastically during the last century. Methylomirabilis bacteria can play an important role in controlling the emission of these two gases from natural ecosystems, by oxidizing methane to CO and reducing nitrite to N without producing NO. These bacteria have an anaerobic metabolism, but are proposed to possess an oxygen-dependent pathway for methane activation. Methylomirabilis bacteria reduce nitrite to NO, and are proposed to dismutate NO into O and N by a putative NO dismutase (NO-D). The O produced in the cell can then be used to activate methane by a particulate methane monooxygenase. So far, the metabolic model of Methylomirabilis bacteria was based mainly on (meta)genomics and physiological experiments. Here we applied a complexome profiling approach to determine which of the proposed enzymes are actually expressed in Methylomirabilis lanthanidiphila. To validate the proposed metabolic model, we focused on enzymes involved in respiration, as well as nitrogen and carbon transformation. All complexes suggested to be involved in nitrite-dependent methane oxidation, were identified in M. lanthanidiphila, including the putative NO-D. Furthermore, several complexes involved in nitrate reduction/nitrite oxidation and NO reduction were detected, which likely play a role in detoxification and redox homeostasis. In conclusion, complexome profiling validated the expression and composition of enzymes hypothesized to be involved in the energy, methane and nitrogen metabolism of M. lanthanidiphila, thereby further corroborating their unique metabolism involved in the environmentally relevant process of nitrite-dependent methane oxidation.
在过去的一个世纪中，强效温室气体甲烷和氧化亚氮（NO）的大气浓度急剧上升。甲基杆菌可以通过将甲烷氧化为 CO 和将亚硝酸盐还原为 N 而不产生 NO，从而在控制这两种气体从自然生态系统中排放方面发挥重要作用。这些细菌具有厌氧代谢，但据推测它们具有依赖氧气的甲烷激活途径。甲基杆菌将亚硝酸盐还原为 NO，并据推测通过假定的一氧化氮歧化酶（NO-D）将 NO 歧化为 O 和 N。细胞中产生的 O 然后可以通过颗粒状甲烷单加氧酶来激活甲烷。到目前为止，甲基杆菌的代谢模型主要基于（宏）基因组学和生理实验。在这里，我们应用了复杂组学分析方法来确定实际上在甲基杆菌中表达的拟议酶。为了验证拟议的代谢模型，我们重点研究了参与呼吸以及氮和碳转化的酶。在 M. lanthanidiphila 中鉴定出了所有被认为与亚硝酸盐依赖的甲烷氧化有关的复合物，包括假定的 NO-D。此外，还检测到了几个参与硝酸盐还原/亚硝酸盐氧化和 NO 还原的复合物，它们可能在解毒和氧化还原稳态中发挥作用。总之，复杂组学分析验证了参与 M. lanthanidiphila 能量、甲烷和氮代谢的假定酶的表达和组成，从而进一步证实了它们在与环境相关的亚硝酸盐依赖的甲烷氧化过程中独特的代谢。
