Thaumarchaeota synthesize specific glycerol dibiphytanyl glycerol tetraethers (GDGTs), the distribution of which is affected by temperature, thereby forming the basis of the paleotemperature proxy, TEX86. Lipids in marine surface sediments are believed to be derived mainly from pelagic Thaumarchaeota; however, some studies have evaluated the possibility that benthic Archaea also contribute to the lipid fossil record. Here, we compared the archaeal abundance and composition from DNA-based methods with the archaeal intact polar lipid (IPL) diversity in surface sediments of a seasonally hypoxic marine lake to determine the potential biological sources of the sedimentary archaeal IPLs under changing environmental conditions. The archaeal community changed from March (oxic conditions) to August (euxinic) from a Thaumarchaeota-dominated community (up to 82%) to an archaeal community dominated by the DPANN super phylum (up to 95%). This marked change coincided with a one order of magnitude decrease in the total IPL-GDGT abundance. In addition, IPL-GDGTs with a glyco polar head group increased. This may indicate a transition to Thaumarchaeota growing in stationary phase or selective preservation of the GDGT pool. In addition, considering the apparent inability of the DPANN Archaea to synthesize their own membrane lipids, we hypothesize that the dominant DPANN Archaea population present in August use the lipids synthesized previously by the Thaumarchaeota or other Archaea to form their own cell membranes, which would indicate an active recycling of fossil IPLs in the marine surface sediment.

中文翻译：

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DPANN 古细菌在季节性缺氧表层海洋沉积物中潜在的 thaumarchaeotal 脂质循环

Thaumarchaeota 合成特定的甘油二联植烷甘油四醚 (GDGT)，其分布受温度影响，从而形成古温度代理 TEX86 的基础。海洋表层沉积物中的脂质被认为主要来自远洋奇古菌；然而，一些研究评估了底栖古生菌也有助于脂质化石记录的可能性。在这里，我们比较了基于 DNA 方法的古菌丰度和组成与季节性缺氧海洋湖泊表层沉积物中古菌完整极性脂质 (IPL) 的多样性，以确定在不断变化的环境条件下沉积古菌 IPL 的潜在生物来源。古菌群落从 3 月（含氧条件）到 8 月（euxinic），从奇古菌属主导的群落（高达 82%）变为以 DPANN 超级门为主的古菌群落（高达 95%）。这一显着变化与总 IPL-GDGT 丰度下降一个数量级相吻合。此外，具有糖极性头部基团的 IPL-GDGT 增加。这可能表明向稳定期生长的奇古菌过渡或选择性保存 GDGT 池。此外，考虑到 DPANN 古菌明显无法合成它们自己的膜脂，我们假设 8 月份存在的主要 DPANN 古菌种群使用先前由奇古菌或其他古菌合成的脂质来形成它们自己的细胞膜，