Simon F. S. Li Marine Science Laboratory, School of Life Sciences and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong SAR 999077, China.
School of Earth and Environmental Sciences and Centre for Exoplanet Science, University of St Andrews, Bute Building, Queen's Terrace KY16 9TS, United Kingdom.
Mol Biol Evol. 2022 Aug 3;39(8). doi: 10.1093/molbev/msac170.
The anaerobic ammonium oxidation (anammox) bacteria can transform ammonium and nitrite to dinitrogen gas, and this obligate anaerobic process accounts for up to half of the global nitrogen loss in surface environments. Yet its origin and evolution, which may give important insights into the biogeochemistry of early Earth, remain enigmatic. Here, we performed a comprehensive phylogenomic and molecular clock analysis of anammox bacteria within the phylum Planctomycetes. After accommodating the uncertainties and factors influencing time estimates, which include implementing both a traditional cyanobacteria-based and a recently developed mitochondria-based molecular dating approach, we estimated a consistent origin of anammox bacteria at early Proterozoic and most likely around the so-called Great Oxidation Event (GOE; 2.32-2.5 Ga) which fundamentally changed global biogeochemical cycles. We further showed that during the origin of anammox bacteria, genes involved in oxidative stress adaptation, bioenergetics, and anammox granules formation were recruited, which might have contributed to their survival on an increasingly oxic Earth. Our findings suggest the rising levels of atmospheric oxygen, which made nitrite increasingly available, was a potential driving force for the emergence of anammox bacteria. This is one of the first studies that link the GOE to the evolution of obligate anaerobic bacteria.
厌氧氨氧化（anammox）细菌可以将氨和亚硝酸盐转化为氮气，这种专性厌氧过程占地球表面环境中全球氮损失的一半以上。然而，其起源和进化，可能为早期地球的生物地球化学提供重要的见解，仍然是个谜。在这里，我们对盘状螺旋体门（Planctomycetes）中的厌氧氨氧化细菌进行了全面的系统发育基因组学和分子钟分析。在考虑到影响时间估计的不确定性和因素后，包括实施传统的蓝细菌为基础和最近开发的线粒体为基础的分子定年方法，我们估计厌氧氨氧化细菌的起源于早期的元古代，最有可能在所谓的大氧化事件（Great Oxidation Event，GOE；23.2-2.5 亿年前）前后，这一事件从根本上改变了全球生物地球化学循环。我们进一步表明，在厌氧氨氧化细菌的起源过程中，与氧化应激适应、生物能量学和厌氧氨氧化颗粒形成相关的基因被招募，这可能有助于它们在越来越氧化的地球上生存。我们的研究结果表明，大气氧气水平的上升，使得亚硝酸盐越来越容易获得，这可能是厌氧氨氧化细菌出现的一个潜在驱动力。这是首次将大氧化事件与专性厌氧细菌的进化联系起来的研究之一。
