Geological Survey of Denmark and Greenland, Copenhagen, Denmark
University of Copenhagen, Department of Plant and Environmental Sciences, Copenhagen, Denmark.
Appl Environ Microbiol. 2019 Mar 6;85(6). doi: 10.1128/AEM.02658-18. Print 2019 Mar 15.
This study assessed the dispersal of five bacterial communities from contrasting compartments along a fractured clay till depth profile comprising plow layer soil, preferential flow paths (biopores and the tectonic fractures below), and matrix sediments, down to 350 cm below the surface. A recently developed expansion of the porous surface model (PSM) was used to capture bacterial communities dispersing under controlled hydration conditions on a soil-like surface. All five communities contained bacteria capable of active dispersal under relatively low hydration conditions (-3.1 kPa). Further testing of the plow layer community revealed active dispersal even at matric potentials of -6.3 to -8.4 kPa, previously thought to be too dry for dispersal on the PSM. Using 16S rRNA gene amplicon sequencing, the dispersing communities were found to be less diverse than their corresponding total communities. The dominant dispersers in most compartments belonged to the genus and, in the plow layer soil, to as well. An exception to this was the dispersing community in the matrix at 350 cm below the surface, which was dominated by Hydrologically connected compartments shared proportionally more dispersing than nondispersing amplicon sequence variants (ASVs), suggesting that active dispersal is important for colonizing these compartments. These results highlight the importance of including soil profile heterogeneity when assessing the role of active dispersal and contribute to discerning the importance of active dispersal in the soil environment. The ability to disperse is considered essential for soil bacteria colonization and survival, yet very little is known about the dispersal ability of communities from different heterogeneous soil compartments. Important factors for dispersal are the thickness and connectivity of the liquid film between soil particles. The present results from a fractured clay till depth profile suggest that dispersal ability is common in various soil compartments and that most are dominated by a few dispersing taxa. Importantly, an increase in shared dispersers among the preferential flow paths of the clay till suggests that active dispersal plays a role in the successful colonization of these habitats.
本研究评估了五个细菌群落从对比的隔室沿着一个破碎的粘土延伸深度剖面的扩散，该剖面包括耕层土壤、优先流路径（生物孔和下面的构造裂缝）和基质沉积物，直到表面以下 350cm 处。最近扩展的多孔表面模型（PSM）被用于在类似于土壤的表面上在受控水合条件下捕获细菌群落的扩散。所有五个群落都包含在相对较低的水合条件（-3.1kPa）下能够主动扩散的细菌。对耕层群落的进一步测试表明，即使在基质势为-6.3 至-8.4kPa 的情况下也能进行主动扩散，以前认为在 PSM 上扩散太干燥。使用 16S rRNA 基因扩增子测序，发现扩散群落的多样性低于其相应的总群落。大多数隔室中占优势的扩散者属于属，而在耕层土壤中，也属于属。这一现象的例外是在 350cm 以下基质中的扩散群落，其主要由属主导。在水力学上相连的隔室中，共享的比例更多的是扩散而不是非扩散的扩增子序列变体（ASVs），这表明主动扩散对于这些隔室的定殖很重要。这些结果强调了在评估主动扩散的作用时考虑土壤剖面异质性的重要性，并有助于区分主动扩散在土壤环境中的重要性。扩散能力被认为是土壤细菌定殖和生存的关键，但对于来自不同异质土壤隔室的群落的扩散能力知之甚少。扩散的重要因素是土壤颗粒之间的液膜的厚度和连通性。来自破碎的粘土延伸深度剖面的当前结果表明，扩散能力在各种土壤隔室中很常见，并且大多数隔室由少数扩散分类群主导。重要的是，粘土延伸的优先流路径中共享的扩散者数量的增加表明，主动扩散在这些栖息地的成功定殖中起着作用。
