Petro Caitlin, Zäncker Birthe, Starnawski Piotr, Jochum Lara M, Ferdelman Timothy G, Jørgensen Bo Barker, Røy Hans, Kjeldsen Kasper U, Schramm Andreas
Center for Geomicrobiology, Department of Bioscience, Aarhus University, Aarhus, Denmark.
Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany.
Front Microbiol. 2019 Apr 12;10:758. doi: 10.3389/fmicb.2019.00758. eCollection 2019.
Analyses of microbial diversity in marine sediments have identified a core set of taxa unique to the marine deep biosphere. Previous studies have suggested that these specialized communities are shaped by processes in the surface seabed, in particular that their assembly is associated with the transition from the bioturbated upper zone to the nonbioturbated zone below. To test this hypothesis, we performed a fine-scale analysis of the distribution and activity of microbial populations within the upper 50 cm of sediment from Aarhus Bay (Denmark). Sequencing and qPCR were combined to determine the depth distributions of bacterial and archaeal taxa (16S rRNA genes) and sulfate-reducing microorganisms (SRM) ( gene). Mapping of radionuclides throughout the sediment revealed a region of intense bioturbation at 0-6 cm depth. The transition from bioturbated sediment to the subsurface below (7 cm depth) was marked by a shift from dominant surface populations to common deep biosphere taxa (e.g., Chloroflexi and Atribacteria). Changes in community composition occurred in parallel to drops in microbial activity and abundance caused by reduced energy availability below the mixed sediment surface. These results offer direct evidence for the hypothesis that deep subsurface microbial communities present in Aarhus Bay mainly assemble already centimeters below the sediment surface, below the bioturbation zone.
对海洋沉积物中微生物多样性的分析已经确定了一套独特的、存在于海洋深部生物圈的核心分类群。先前的研究表明，这些特殊的群落是由表层海床中的过程塑造的，特别是它们的组装与从生物扰动的上层区域到下面未受生物扰动区域的过渡有关。为了验证这一假设，我们对丹麦奥胡斯湾沉积物上部50厘米内微生物种群的分布和活性进行了精细分析。结合测序和定量PCR来确定细菌和古菌类群（16S rRNA基因）以及硫酸盐还原微生物（SRM）（基因）的深度分布。对整个沉积物中的放射性核素进行测绘，揭示了0-6厘米深度处强烈生物扰动的区域。从生物扰动的沉积物到下面的次表层（7厘米深度）的过渡，其特征是从占主导地位的表层种群转变为常见的深部生物圈分类群（如绿弯菌门和无名杆菌纲）。群落组成的变化与混合沉积物表面以下能量可用性降低导致的微生物活性和丰度下降同时发生。这些结果为以下假设提供了直接证据：奥胡斯湾中存在的深部次表层微生物群落主要在沉积物表面以下几厘米处、生物扰动带以下组装而成。
