Nitrogen is essential for all organisms, but biological nitrogen fixation (BNF) occurs only in a small fraction of prokaryotes. Previous studies divided nitrogenase-gene-carrying prokaryotes into Groups I to IV and provided evidence that BNF first evolved in bacteria. This study constructed a timetree of the evolution of nitrogen-fixation genes and estimated that archaea evolved BNF much later than bacteria and that nitrogen-fixing cyanobacteria evolved later than 1900 million years ago (MYA), considerably younger than the previous estimate of 2200 MYA. Moreover, Groups III and II/I diverged ∼2280 MYA, after the Kenorland supercontinent breakup (∼2500-2100 MYA) and the Great Oxidation Event (∼2400-2100 MYA); Groups III and Vnf/Anf diverged ∼2086 MYA, after the Yarrabubba impact (∼2229 MYA); and Groups II and I diverged ∼1920 MYA, after the Vredefort impact (∼2023 MYA). In summary, this study provided a timescale of BNF events and discussed the possible effects of geological events on BNF evolution.

中文翻译：

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将地质事件和固氮进化映射到固氮基因进化的时间树上

氮对于所有生物体都是必需的，但生物固氮（BNF）仅发生在一小部分原核生物中。先前的研究将携带固氮酶基因的原核生物分为第一组至第四组，并提供了BNF首先在细菌中进化的证据。这项研究构建了固氮基因进化的时间树，并估计古细菌进化BNF的时间比细菌晚得多，而固氮蓝藻的进化时间晚于19亿年前（MYA），比之前估计的2200 MYA要年轻得多。此外，在凯诺兰超大陆分裂（~2500-2100 MYA）和大氧化事件（~2400-2100 MYA）之后，第三组和第二/I组分歧~2280 MYA；在 Yarrabubba 撞击之后（~2229 MYA），III 组和 Vnf/Anf 分歧~2086 MYA；在弗里德堡撞击之后（~2023 年），第 II 组和第 I 组在~1920 年发生了分歧。总之，本研究提供了 BNF 事件的时间尺度，并讨论了地质事件对 BNF 演化的可能影响。