Frindte Katharina, Allgaier Martin, Grossart Hans-Peter, Eckert Werner
Department of Soil Science, Institute for Crop Science and Resource Conservation (INRES), University of Bonn, Nußallee 13, Bonn, Germany.
Berlin Center for Genomics in Biodiversity Research (BeGenDiv), Königin-Luise-Straße 6-8, Berlin, Germany.
PLoS One. 2015 Nov 24;10(11):e0143428. doi: 10.1371/journal.pone.0143428. eCollection 2015.
The sediment-water interface of freshwater lakes is characterized by sharp chemical gradients, shaped by the interplay between physical, chemical and microbial processes. As dissolved oxygen is depleted in the uppermost sediment, the availability of alternative electron acceptors, e.g. nitrate and sulfate, becomes the limiting factor. We performed a time series experiment in a mesocosm to simulate the transition from aerobic to anaerobic conditions at the sediment-water interface. Our goal was to identify changes in the microbial activity due to redox transitions induced by successive depletion of available electron acceptors. Monitoring critical hydrochemical parameters in the overlying water in conjunction with a new sampling strategy for sediment bacteria enabled us to correlate redox changes in the water to shifts in the active microbial community and the expression of functional genes representing specific redox-dependent microbial processes. Our results show that during several transitions from oxic-heterotrophic condition to sulfate-reducing condition, nitrate-availability and the on-set of sulfate reduction strongly affected the corresponding functional gene expression. There was evidence of anaerobic methane oxidation with NOx. DGGE analysis revealed redox-related changes in microbial activity and expression of functional genes involved in sulfate and nitrite reduction, whereas methanogenesis and methanotrophy showed only minor changes during redox transitions. The combination of high-frequency chemical measurements and molecular methods provide new insights into the temporal dynamics of the interplay between microbial activity and specific redox transitions at the sediment-water interface.
淡水湖泊的沉积物 - 水界面具有明显的化学梯度，其形成是物理、化学和微生物过程相互作用的结果。由于最上层沉积物中的溶解氧被消耗，替代电子受体（如硝酸盐和硫酸盐）的可用性成为限制因素。我们在中宇宙中进行了一项时间序列实验，以模拟沉积物 - 水界面从有氧到厌氧条件的转变。我们的目标是确定由于可用电子受体的连续消耗引起的氧化还原转变导致的微生物活性变化。结合一种新的沉积物细菌采样策略，监测上覆水中的关键水化学参数，使我们能够将水中的氧化还原变化与活跃微生物群落的变化以及代表特定氧化还原依赖性微生物过程的功能基因的表达相关联。我们的结果表明，在从有氧异养条件到硫酸盐还原条件的几次转变过程中，硝酸盐的可用性和硫酸盐还原的开始强烈影响了相应功能基因的表达。有证据表明存在与氮氧化物有关的厌氧甲烷氧化。DGGE分析揭示了与氧化还原相关的微生物活性变化以及参与硫酸盐和亚硝酸盐还原的功能基因的表达，而在氧化还原转变过程中，甲烷生成和甲烷氧化仅显示出微小变化。高频化学测量和分子方法的结合为沉积物 - 水界面微生物活性与特定氧化还原转变之间相互作用的时间动态提供了新的见解。
