Archaeal and bacterial H-GDGTs are abundant in peat and their relative abundance is positively correlated with temperature
Archaeal and bacterial H-GDGTs are abundant in peat and their relative abundance is positively correlated with temperature
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DOI：
10.1016/j.gca.2018.02.025
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发表时间：
2018-04
影响因子：
5
通讯作者：
B. Naafs;D. McCormick;G. Inglis;R. Pancost
中科院分区：
文献类型：
--
作者：
B. Naafs;D. McCormick;G. Inglis;R. Pancost
甘油单烷基甘油四醚脂质（GMGT;也称为“H-GDGT”）与更常见的甘油二烷基甘油四醚（GDGT）不同，因为它们具有连接两个烷基链的额外共价键。此前已发现六种不同的古细菌类异戊二烯H-GDGT（H-isoGDGT）和一种分支H-GDGT（H-brGDGT），推测是由细菌产生的。然而，H-GDGT在生命的两个领域中的功能尚不清楚。据认为，这种额外共价键的形成导致膜稳定性增强，这是H-GDGT在极端环境如地热环境中高丰度的原因，但到目前为止，还没有证据支持这一假设。在这里，我们报告了全球泥炭数据库（n= 471）中H-GDGT的分布，其年平均气温（MAAT）范围很广。这是H-GDGT在土壤（特别是泥炭）中的首次发现，强调了H-GDGT在中温环境中的广泛存在。此外，我们报告的存在下，两个新的H-brGDGT与一个（H-1034）和两个（H-1048）额外的甲基，分别。我们的研究结果表明，细菌和古细菌的H-GDGT的相对丰度相比，常规GDGT与温度有关的H-GDGT的相对丰度最高的热带泥炭。虽然除了温度之外的其他因素也可能起作用，但这些结果确实支持H-GDGT是对温度的适应以维持膜稳定性的假设。细菌和古细菌膜脂对温度的反应表明，这两个生命领域之间的脂质分界线具有相同的适应性，这表明平行或趋同进化（可能通过横向基因转移促进）。
Glycerol monoalkyl glycerol tetraether lipids (GMGTs; also called ‘H-GDGTs’) differ from the more commonly studied glycerol dialkyl glycerol tetraether (GDGTs) in that they have an additional covalent bond that links the two alkyl chains. Six different archaeal isoprenoidal H-GDGTs (H-isoGDGTs) and one branched H-GDGT (H-brGDGT), presumably produced by bacteria, have previously been found. However, the function of H-GDGTs in both domains of life is unknown. It is thought that the formation of this additional covalent bond results in enhanced membrane stability, accounting for the high abundance of H-GDGTs in extreme environments such as geothermal settings, but so far there has been little evidence to support this hypothesis.Here we report the distribution of H-GDGTs in a global peat database (n= 471) with a broad range in mean annual air temperature (MAAT) and pH. This is the first finding of H-GDGTs in soils (specifically, peat), highlighting that H-GDGTs are widespread in mesophilic settings. In addition, we report the presence of two new H-brGDGTs with one (H-1034) and two (H-1048) additional methyl groups, respectively. Our results suggest that the relative abundance of both bacterial and archaeal H-GDGTs compared to regular GDGTs is related to temperature with the highest relative abundance of H-GDGTs in tropical peats. Although other factors besides temperature likely also play a role, these results do support the hypothesis that H-GDGTs are an adaptation to temperature to maintain membrane stability. The observation that both bacterial and archaeal membrane lipids respond to temperature indicates the same adaption across the lipid divide between these two domains of life, suggesting parallel or convergent evolution (potentially facilitated by lateral gene transfer).