Molecular paleontological research for the evolution of symbiosis of chanosynthetic biological community

近年来的生物标志物和同位素研究表明，太古代参与了海洋沉积物中的甲烷厌氧氧化过程。自生碳酸盐沉淀与AOM有关，AOM产生CO_2，降低pH，有利于碳酸盐的溶解而不是沉淀。甲烷的厌氧氧化使碳酸盐的碱度增加，有利于自生碳酸盐的沉淀。海底甲烷渗漏和甲烷氧化与碳酸盐沉淀的关系是在碳酸盐碳耗竭的基础上建立<13>的。冷泉碳酸盐岩中含有甲烷厌氧氧化的生物标志物，甲烷厌氧氧化在冷泉碳酸盐岩沉积过程中起着重要作用。鉴定AOM的最重要的诊断性脂类化合物是贫<13>碳的五甲基二十烷（PME），最可能的是西红花烷。另一种鉴定甲烷氧化古细菌的有用化合物是贫<13>碳的类异戊二烯醚脂或来自具有类异戊二烯碳骨架的醚结合膜脂的降解产物。新开发的指示AOM，特别是ANME-2（产甲烷菌群）的生物标志物是C13和C18类异戊二烯酮。本研究从更新世Koshiba组、利尻海峡现代海底、北海道白垩纪灰岩中提取了AOM的生物标志物。与AOM有关的古生物种类繁多，生物标志物是区分地质样品中AMNE-1和ANME-2的有效工具。早白垩世的化粪池化石群落以ANME-1型为主，晚白垩世的化粪池化石群落以ANME-2型为主。化学合成群落的组合正在演变。

Recent biomarker and isotopic studies indicated the participation of Archea in an anaerobic methane-oxidation (AOM) in the marine sediments. Authigenic carbonate precipitation was related to AOM which produces CO_2 and decreases pH, favoring the dissolution of carbonates rather than precipitation. Anaerobically oxidized methane produces the increase in alkalinity of carbonate and favors the precipitation of authigenic carbonates. The association of methane seepage on the sea floor and an oxidation of methane with carbonate precipitation was established on the basis of carbonate ^<13>C depletion. The cold-seep carbonates contain biomarkers suggesting the anaerobic methane-oxidation which play an important role during cold-seep carbonate precipitation. The most important diagnostic lipid compound for identifying AOM is ^<13>C depleted pentamethyleicosane (PME) and most likely crocetane Another useful compound to identify methane oxidizing Archea is ^<13>C depleted isoprenoid ether lipid or degradation product originated from ether-bound membrane lipids with an isoporenoid carbon skeleton.Newly developed biomarker indicating AOM, especially ANME-2 (group of methanogens), is C13 and C18 isoprenoid ketone. The origin of isoprenoid ketone could be hydroxyarchaeol contained Methanosarcinaceae.Biomarker indicating AOM was investigated from Pleistocene Koshiba formation, Recent sea-floor from Rishiri channel, five Cretaceous limestone from Hokkaido in this study. The Archeal spices related to AOM are multiple, biomarker is useful tool for distinguish AMNE-1 and ANME-2 in geological samples. The fossil chemosynthtic communities at the age of Lower Cretaceous are dominated ANME-1, and the samples from younger than Upper Cretaceous are dominated ANME-2. The combination of chemosynthetic community is evolving.