Zeng Zichao, Li Liuyang, Wang Heng, Tao Yuxin, Lv Zhenbo, Wang Fengping, Wang Yinzhao
State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
School of Oceanography, Shanghai Jiao Tong University, Shanghai 200240, China.
PNAS Nexus. 2025 Feb 3;4(2):pgaf035. doi: 10.1093/pnasnexus/pgaf035. eCollection 2025 Feb.
The metabolic transition from anaerobic to aerobic in prokaryotes reflects adaptations to oxidative stress. Methanogen, one of the earliest life forms on Earth, has evolved into three major groups within the , exhibiting different phylogenetic affiliations and metabolic characters. In comparison with other strictly anaerobic methanogenic groups, the Class II methanogens possess a better capability to adapt to limited oxygen pressure. is considered the first and only prokaryote evolving oxygenic photosynthesis and is responsible for the Great Oxidation Event on Earth. However, the connection between oxygenic and evolutionary adaptations to oxidative stress in prokaryotes remains elusive. Here, through the gene encoding structural maintenance of chromosomes (SMC) protein, which was horizontally transferred from ancient Class II methanogens to the last common ancestor of the crown-group , we demonstrate that the origin of extant was undoubtedly posterior to the occurrence of oxygen-tolerant Class II methanogens. In addition, we found that certain prokaryotic lineages had evolved the tolerance mechanisms against oxidative stress before the origin of extant . The contradiction that oxidative adaptations in Class II methanogens and other prokaryotes predating the crown-group oxygenic implies the existence of more ancient biological oxygenesis. We propose that these potential oxygenic organisms might represent the extinct phototrophs and first emerge during the Paleoarchean, contributing to the oxidative adaptations in the prokaryotic tree of life and facilitating the dispersal of reaction centers across the bacterial domain.
原核生物从厌氧到需氧的代谢转变反映了对氧化应激的适应。产甲烷菌是地球上最早的生命形式之一，已进化为该类群中的三个主要组，表现出不同的系统发育关系和代谢特征。与其他严格厌氧的产甲烷菌群相比，II类产甲烷菌具有更好的适应有限氧压的能力。蓝细菌被认为是第一种也是唯一进化出有氧光合作用的原核生物，它引发了地球上的大氧化事件。然而，有氧光合作用与原核生物对氧化应激的进化适应之间的联系仍然难以捉摸。在这里，通过编码染色体结构维持（SMC）蛋白的基因，该基因从古老的II类产甲烷菌水平转移到冠群蓝细菌的最后一个共同祖先，我们证明现存蓝细菌的起源无疑晚于耐氧II类产甲烷菌的出现。此外，我们发现某些原核生物谱系在现存蓝细菌起源之前就已经进化出了对抗氧化应激的耐受机制。II类产甲烷菌和其他早于冠群有氧蓝细菌的原核生物中的氧化适应之间的矛盾意味着存在更古老的生物氧化作用。我们提出，这些潜在的有氧生物可能代表已灭绝的光合生物，最早出现在古太古代，促成了原核生物生命之树中的氧化适应，并促进了反应中心在细菌域中的传播。
