Center for Geomicrobiology, Department of Bioscience, Aarhus University, 8000, Aarhus, Denmark.
Department of Geosciences and Natural Resource Management, University of Copenhagen, 1350, Copenhagen, Denmark.
Sci Rep. 2017 May 25;7(1):2400. doi: 10.1038/s41598-017-02295-x.
The factors controlling the relative abundances of Archaea and Bacteria in marine sediments are poorly understood. We determined depth distributions of archaeal and bacterial 16S rRNA genes by quantitative PCR at eight stations in Aarhus Bay, Denmark. Bacterial outnumber archaeal genes 10-60-fold in uppermost sediments that are irrigated and mixed by macrofauna. This bioturbation is indicated by visual observations of sediment color and faunal tracks, by porewater profiles of dissolved inorganic carbon and sulfate, and by distributions of unsupported Pb and Cs. Below the depth of bioturbation, the relative abundances of archaeal genes increase, accounting for one third of 16S rRNA genes in the sulfate zone, and half of 16S rRNA genes in the sulfate-methane transition zone and methane zone. Phylogenetic analyses reveal a strong shift in bacterial and archaeal community structure from bioturbated sediments to underlying layers. Stable isotopic analyses on organic matter and porewater geochemical gradients suggest that macrofauna mediate bacterial dominance and affect microbial community structure in bioturbated sediment by introducing fresh organic matter and high-energy electron acceptors from overlying seawater. Below the zone of bioturbation, organic matter content and the presence of sulfate exert key influences on bacterial and archaeal abundances and overall microbial community structure.
海洋沉积物中古菌和细菌相对丰度的控制因素还了解甚少。我们在丹麦奥尔胡斯湾的 8 个站位通过定量 PCR 确定了古菌和细菌 16S rRNA 基因的深度分布。在受大型动物灌溉和混合的最上层沉积物中，细菌的数量是古菌的 10-60 倍。这种生物扰动可以通过沉积物颜色和动物足迹的视觉观察、溶解无机碳和硫酸盐的孔隙水剖面以及无支撑 Pb 和 Cs 的分布来指示。在生物扰动深度以下，古菌基因的相对丰度增加，在硫酸盐区占 16S rRNA 基因的三分之一，在硫酸盐-甲烷过渡区和甲烷区占一半。系统发育分析显示，细菌和古菌群落结构从生物扰动沉积物到下覆层发生了强烈转变。有机物质的稳定同位素分析和孔隙水地球化学梯度表明，大型动物通过从上层海水中引入新鲜有机物质和高能电子受体来介导细菌优势，并影响生物扰动沉积物中的微生物群落结构。在生物扰动带以下，有机质含量和硫酸盐的存在对细菌和古菌丰度以及整体微生物群落结构有重要影响。
