Marshall Ian P G, Karst Søren M, Nielsen Per H, Jørgensen Bo Barker
Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 114, 8000 Aarhus C, Denmark.
Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.
Mar Genomics. 2018 Feb;37:58-68. doi: 10.1016/j.margen.2017.08.004. Epub 2017 Aug 12.
Microbial communities that lived near the sediment surface in the past become slowly buried and are the source of deep subsurface communities thousands of years later. We used metagenomes to analyse how the composition of buried microbial communities may change to conform to altered environmental conditions at depth. Sediment samples were collected from down to 85m below sea floor during the Integrated Ocean Drilling Program Expedition 347, "Baltic Sea Paleoenvironment". The sediments vary in age, organic carbon content, porewater salinity, and other parameters that reflect the changing Baltic environment from the last ice age and throughout the Holocene. We found microorganisms capable of energy conservation by fermentation, acetogenesis, methanogenesis, anaerobic oxidation of methane, and reductive dehalogenation. Glacial sediments showed a greater relative abundance of genes encoding enzymes in the Wood-Ljungdahl pathway and pyruvate:ferredoxin oxidoreductase than Holocene sediments. Relative abundance of genes conferring salinity tolerance was found to correlate with the present salinity, even in deep late-glacial sediment layers where salinity has increased since the sediment was deposited in a freshwater lake >9000years ago. This suggests that deeply buried and isolated sediment communities can slowly change in composition in response to geochemical changes that happen long after deposition.
过去生活在沉积物表面附近的微生物群落会逐渐被掩埋，数千年后成为深部地下群落的来源。我们利用宏基因组分析被掩埋的微生物群落组成如何变化，以适应深部环境条件的改变。在综合大洋钻探计划第347航次“波罗的海古环境”期间，从海底以下85米深处采集了沉积物样本。这些沉积物在年龄、有机碳含量、孔隙水盐度以及其他反映自上一个冰期至全新世期间波罗的海环境变化的参数方面存在差异。我们发现了能够通过发酵、产乙酸、产甲烷、甲烷厌氧氧化和还原性脱卤作用进行能量守恒的微生物。与全新世沉积物相比，冰川沉积物中编码伍德-Ljungdahl途径和丙酮酸：铁氧化还原蛋白氧化还原酶的基因相对丰度更高。研究发现，即使在9000多年前沉积于淡水湖的沉积物形成后盐度已经升高的深部晚冰期沉积层中，赋予耐盐性的基因相对丰度也与当前盐度相关。这表明，深埋且隔离的沉积物群落可以随着沉积后很久才发生的地球化学变化而在组成上缓慢改变。
