Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139;Center for Microbial Oceanography: Research and Education, University of Hawaii at Manoa, Honolulu, HI 96822;
Center for Microbial Oceanography: Research and Education, University of Hawaii at Manoa, Honolulu, HI 96822;Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822; and.
Proc Natl Acad Sci U S A. 2014 Jul 8;111(27):9858-63. doi: 10.1073/pnas.1409439111. Epub 2014 Jun 19.
Archaea are ubiquitous in marine plankton, and fossil forms of archaeal tetraether membrane lipids in sedimentary rocks document their participation in marine biogeochemical cycles for >100 million years. Ribosomal RNA surveys have identified four major clades of planktonic archaea but, to date, tetraether lipids have been characterized in only one, the Marine Group I Thaumarchaeota. The membrane lipid composition of the other planktonic archaeal groups--all uncultured Euryarchaeota--is currently unknown. Using integrated nucleic acid and lipid analyses, we found that Marine Group II Euryarchaeota (MG-II) contributed significantly to the tetraether lipid pool in the North Pacific Subtropical Gyre at shallow to intermediate depths. Our data strongly suggested that MG-II also synthesize crenarchaeol, a tetraether lipid previously considered to be a unique biomarker for Thaumarchaeota. Metagenomic datasets spanning 5 y indicated that depth stratification of planktonic archaeal groups was a stable feature in the North Pacific Subtropical Gyre. The consistent prevalence of MG-II at depths where the bulk of exported organic matter originates, together with their ubiquitous distribution over diverse oceanic provinces, suggests that this clade is a significant source of tetraether lipids to marine sediments. Our results are relevant to archaeal lipid biomarker applications in the modern oceans and the interpretation of these compounds in the geologic record.
古菌在海洋浮游生物中无处不在，沉积岩中古菌四醚膜脂的化石形式证明了它们参与海洋生物地球化学循环的时间超过了 1 亿年。核糖体 RNA 调查已经确定了浮游古菌的四个主要分支，但迄今为止，只有一个分支，即海洋 I 组广古菌，其四醚脂类得到了描述。其他浮游古菌群——所有未培养的广古菌——的膜脂组成目前尚不清楚。通过综合核酸和脂类分析，我们发现海洋 II 组广古菌（MG-II）在北太平洋亚热带环流的浅至中层深度对四醚脂类库有重要贡献。我们的数据强烈表明，MG-II 也合成 crenarchaeol，这是一种以前被认为是广古菌特有生物标志物的四醚脂。跨越 5 年的宏基因组数据集表明，浮游古菌群在北太平洋亚热带环流中的深度分层是一个稳定的特征。MG-II 在大部分输出有机物质起源的深度普遍存在，并且在各种海洋区域广泛分布，这表明该分支是海洋沉积物中四醚脂类的重要来源。我们的研究结果与现代海洋中古菌脂类生物标志物的应用以及这些化合物在地质记录中的解释有关。
