Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada;
Department of Geoscience, University of Calgary, Calgary, AB T2N 1N4, Canada.
Proc Natl Acad Sci U S A. 2020 May 19;117(20):11029-11037. doi: 10.1073/pnas.2002289117. Epub 2020 Apr 30.
Marine cold seeps transmit fluids between the subseafloor and seafloor biospheres through upward migration of hydrocarbons that originate in deep sediment layers. It remains unclear how geofluids influence the composition of the seabed microbiome and if they transport deep subsurface life up to the surface. Here we analyzed 172 marine surficial sediments from the deep-water Eastern Gulf of Mexico to assess whether hydrocarbon fluid migration is a mechanism for upward microbial dispersal. While 132 of these sediments contained migrated liquid hydrocarbons, evidence of continuous advective transport of thermogenic alkane gases was observed in 11 sediments. Gas seeps harbored distinct microbial communities featuring bacteria and archaea that are well-known inhabitants of deep biosphere sediments. Specifically, 25 distinct sequence variants within the uncultivated bacterial phyla and and the archaeal order occurred in significantly greater relative sequence abundance along with well-known seep-colonizing members of the bacterial genus , in the gas-positive sediments. Metabolic predictions guided by metagenome-assembled genomes suggested these organisms are anaerobic heterotrophs capable of nonrespiratory breakdown of organic matter, likely enabling them to inhabit energy-limited deep subseafloor ecosystems. These results point to petroleum geofluids as a vector for the advection-assisted upward dispersal of deep biosphere microbes from subsurface to surface environments, shaping the microbiome of cold seep sediments and providing a general mechanism for the maintenance of microbial diversity in the deep sea.
海洋冷泉通过源自深部沉积层的碳氢化合物向上运移，在海底和海底生物圈之间传递流体。目前尚不清楚地质流体如何影响海底微生物组的组成，以及它们是否将深部地下生命输送到地表。在这里，我们分析了来自墨西哥湾东部深海的 172 个海洋表层沉积物，以评估烃类流体迁移是否是微生物向上扩散的一种机制。虽然其中 132 个沉积物含有迁移的液态烃，但在 11 个沉积物中观察到热成因烷烃气体连续平流输送的证据。气体渗漏处存在独特的微生物群落，其中包括已知是深海生物圈沉积物中栖息者的细菌和古菌。具体而言，在气体阳性沉积物中，未培养的细菌门 和 以及古菌目 的 25 个不同序列变体，以及细菌属 的著名的渗漏定植成员，其相对序列丰度显著增加。由宏基因组组装基因组指导的代谢预测表明，这些生物体是厌氧异养生物，能够进行有机物质的非呼吸分解，这可能使它们能够栖息于能量有限的深海海底生态系统中。这些结果表明，石油地质流体是深部生物圈微生物从地下到地表环境进行平流辅助向上扩散的载体，塑造了冷渗沉积物的微生物组，并为深海中微生物多样性的维持提供了一般机制。
