MCG古菌代表了一类自然界较古老的古菌，提议将MCG古菌归类于一个全新的门类——深古菌门（Bathyarchaeota）。高浓度CO2造成的海水酸化对西太平洋海区浮游细菌的丰度、高DNA含量细菌、生产力等有促进作用，但对细菌的多样性有一定程度的抑制作用。火山灰造成海洋异养细菌和真核自养生物的丰度均显著升高，降低浮游病毒的丰度，导致微生物群落多样性降低，使整个群落朝着不同方向演替。发现AOM细胞团在其表面形成粘土矿物，而在周围环境中形成碳酸盐，这可能与AOM反应产生的HS-增加环境碱度有关。西南印度洋深海微生物群落结构与钙、磷、硫等元素具有相关性。提出了两类示踪古水文条件的微生物脂类指标、三类灵敏响应古温度的微生物脂类指标。有机质-粘土矿物复合体能有效保护有机质遭受微生物的作用，对碳循环产生重要影响。不同微生物功能群的共存能促进粘土矿物结构铁的还原，微生物成因的白云石主要与细胞表面的羧基官能团有关。发现古、中生代之交海洋环境具有高温、缺氧、低硫酸盐浓度、氮素匮乏的特征，生态系统不同营养层次的生物对海洋环境具有不同的响应能力，微生物对海洋水化学和全球变暖起重要作用。提出了两幕生物危机与两幕环境变化，温度变化和缺氧环境可能导致了二叠纪-三叠纪之交的幕式生物危机。大灭绝后，在Griesbachian早期、Dienerian-Smithian之交、Smithian-Spathian之交出现严重的海洋缺氧、硫化事件，出现了微生物岩、鲕粒灰岩等异常沉积。在雪球地球之前的拉伸纪古气候已经开始不稳定。埃迪卡拉纪海洋的化学分层造成不同的生境及其不同的地球微生物学过程，造成DOC碳库与DIC碳库的分离，也造成不同于显生宙的海洋碳循环。陡山沱组II和IV段在缺氧或硫化的水体中存在一个大DOC碳库；陡山沱早期（II段）以光合自养微生物体系为主，到晚期（IV段）随着透光带硫化水体的发育，有大量化能异养微生物加入。晚埃迪卡拉纪-早寒武世海洋仍具有缺氧分层的高梯度状态。早寒武世早期可能缺乏固氮作用相关，随后趋于正常，氧化明显并伴生多细胞生物发育。华北中元古界发现大量微生物成因的凝块石，在燕山盆地中元古代发现了两个重要的生物群更替事件，分别与海洋化学变化以及火山活动导致的营养盐输入相关。发现了多种真核生物化石，表明这个时期真核生物已经出现明显的多样性分化。中元古代海洋DIC库经历了逐渐减小的演变，海洋硫酸盐浓度较低，氧化还原界面较浅。在浅水环境自养微生物控制了碳的代谢过程，而深水环境厌氧微生物代谢对海水化学组成有很大影响。%MCG is one of the earlier archaeal branches and taxonomically assigned to a new branch, Bathyarchaeota. CO2-induced oceanic acidification promotes the abundance of planktonic bacteria and the primary production but decreases bacterial diversity. Addition of volcanic ash induces the elevated abundance of heterotrophic bacteria and eukaryotic autotrophs, but decreases the abundance of planktonic viruses and microbial diversity. Microbial cells related to AOM lead to the precipitation of clay mineral on the cell surface but the carbonate in surrounding environments. Microbial lipid proxies were proposed to show sensitive responses to temperature and hydrological conditions. Organic-clay association could prevent organics from microbial degradation, which in turn impacts carbon cycle. Co-occurrence of microbial functional groups accelerates the reduction of iron within clay minerals. It is found that the ocean across the Permian-Triassic boundary is featured by hot, anoxic conditions with low concentration of sulfate and nitrate. Organisms of different trophic levels show varied responses to the deteriorative environmental conditions. Microbes play important roles in changing the oceanic chemistry and global warming at that time. Two episodes of faunal mass extinction and environmental crisis were proposed. Enhanced anoxia and euxinia were present in association with microbialites and giant oolites in early Griesbachian, Dienerian-Smithian transition and Smithian-Spathian. Oceanic stratification in Neoproterozoic results in the differentiation of bio-habitat and thus the different geomicrobiological processes, which in turn causes the separation of DOC pool and DIC pool and thus a carbon cycle different from that in Phanerozoic. Large DOC pool is present in association with anoxic or euxinic conditions during Doushantuo deposition. Photosynthetic autotrophs are dominant in Early Doushantuo but later replaced by chemoheterotrophs due to the expansion of euxinic zones. Thrombolites were demonstrated to be of microbial origin in Mesoproterozoic in North China craton. Two important replacements of microbes were found to relate to the change in oceanic chemistry and the enhanced input of nutrients resulted from volcanism, respectively. Eukaryote was documented to diversify at that period. Mesoproterozoic oceans are characterized by the decrease in DIC pool, the shallow chemocline and low concentration of sulfate.
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