Geological Survey of Denmark and Greenland, Copenhagen, Denmark
University of Copenhagen, Department of Plant and Environmental Sciences, Copenhagen, Denmark.
Appl Environ Microbiol. 2018 Mar 19;84(7). doi: 10.1128/AEM.02857-17. Print 2018 Apr 1.
In this study, we developed a method that provides profiles of community-level surface dispersal from environmental samples under controlled hydration conditions and enables us to isolate and uncover the diversity of the fastest bacterial dispersers. The method expands on the porous surface model (PSM), previously used to monitor the dispersal of individual bacterial strains in liquid films at the surface of a porous ceramic disc. The novel procedure targets complex communities and captures the dispersed bacteria on a solid medium for growth and detection. The method was first validated by distinguishing motile and strains from their nonmotile mutants. Applying the method to soil and lake water bacterial communities showed that community-scale dispersal declined as conditions became drier. However, for both communities, dispersal was detected even under low-hydration conditions (matric potential, -3.1 kPa) previously proven too dry for strain KT2440 motility. We were then able to specifically recover and characterize the fastest dispersers from the inoculated communities. For both soil and lake samples, 16S rRNA gene amplicon sequencing revealed that the fastest dispersers were substantially less diverse than the total communities. The dispersing fraction of the soil microbial community was dominated by species cells, which increased in abundance under low-hydration conditions, while the dispersing fraction of the lake community was dominated by species cells and, under wet conditions (-0.5 kPa), also by species cells. The results gained in this study bring us a step closer to assessing the dispersal ability within complex communities under environmentally relevant conditions. Dispersal is a key process of bacterial community assembly, and yet, very few attempts have been made to assess bacterial dispersal at the community level, as the focus has previously been on pure-culture studies. A crucial factor for dispersal in habitats where hydration conditions vary, such as soils, is the thickness of the liquid films surrounding solid surfaces, but little is known about how the ability to disperse in such films varies within bacterial communities. Therefore, we developed a method to profile community dispersal and identify fast dispersers on a rough surface resembling soil surfaces. Our results suggest that within the motile fraction of a bacterial community, only a minority of the bacterial types are able to disperse in the thinnest liquid films. During dry periods, these efficient dispersers can gain a significant fitness advantage through their ability to colonize new habitats ahead of the rest of the community.
在这项研究中，我们开发了一种方法，该方法可在受控水合条件下提供社区水平表面扩散的图谱，并使我们能够分离和揭示最快细菌扩散体的多样性。该方法扩展了多孔表面模型（PSM），该模型先前用于监测多孔陶瓷盘表面液膜中单个细菌菌株的分散。新方法针对复杂的群落，并在固体培养基上捕获分散的细菌进行生长和检测。该方法首先通过区分其非运动突变体的运动株和非运动株来验证。将该方法应用于土壤和湖水细菌群落表明，随着条件变干燥，群落尺度的扩散减少。但是，对于这两个群落，即使在先前证明对于 KT2440 菌株的运动太干燥的低水合条件（基质势，-3.1 kPa）下，也检测到了扩散。然后，我们能够从接种的群落中专门回收和表征最快的扩散体。对于土壤和湖水样本，16S rRNA 基因扩增子测序显示，最快的扩散体与总群落相比多样性要低得多。土壤微生物群落的扩散部分主要由细胞组成，这些细胞在低水合条件下丰度增加，而湖水群落的扩散部分主要由细胞组成，在潮湿条件（-0.5 kPa）下，也由细胞组成。本研究获得的结果使我们更接近于在与环境相关的条件下评估复杂群落中的扩散能力。扩散是细菌群落组装的关键过程，但是，由于以前的重点是纯培养研究，因此很少有人尝试评估群落水平的细菌扩散。在水合条件变化的栖息地（例如土壤）中扩散的关键因素是围绕固体表面的液膜的厚度，但是对于在这种液膜中扩散的能力在细菌群落中的变化知之甚少。因此，我们开发了一种方法来描绘群落扩散并在类似于土壤表面的粗糙表面上识别快速扩散体。我们的结果表明，在细菌群落的运动部分中，只有少数细菌类型能够在最薄的液膜中扩散。在干燥期，这些有效的扩散体能够通过其在社区其他成员之前殖民新栖息地的能力获得显著的适应优势。
