Lindh Markus V, Sjöstedt Johanna, Casini Michele, Andersson Agneta, Legrand Catherine, Pinhassi Jarone
Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University Kalmar, Sweden.
Department of Aquatic Resources, Institute of Marine Research, Swedish University of Agricultural Sciences (SLU) Lysekil, Sweden.
Front Microbiol. 2016 Dec 23;7:2078. doi: 10.3389/fmicb.2016.02078. eCollection 2016.
Marine microbes exhibit biogeographical patterns linked with fluxes of matter and energy. Yet, knowledge of the mechanisms shaping bacterioplankton community assembly across temporal scales remains poor. We examined bacterioplankton 16S rRNA gene fragments obtained from Baltic Sea transects to determine phylogenetic relatedness and assembly processes coupled with niche breadth. Communities were phylogenetically more related over time than expected by chance, albeit with considerable temporal variation. Hence, habitat filtering, i.e., local environmental conditions, rather than competition structured bacterioplankton communities in summer but not in spring or autumn. Species sorting (SS) was the dominant assembly process, but temporal and taxonomical variation in mechanisms was observed. For May communities, Cyanobacteria, Actinobacteria, Alpha- and Betaproteobacteria exhibited SS while Bacteroidetes and Verrucomicrobia were assembled by SS and mass effect. Concomitantly, Gammaproteobacteria were assembled by the neutral model and patch dynamics. Temporal variation in habitat filtering and dispersal highlights the impact of seasonally driven reorganization of microbial communities. Typically abundant Baltic Sea populations such as the NS3a marine group (Bacteroidetes) and the SAR86 and SAR11 clade had the highest niche breadth. The verrucomicrobial population also exhibited high niche breadth. Surprisingly, variation in bacterioplankton community composition was regulated by environmental factors for generalist taxa but not specialists. Our results suggest that generalists such as NS3a, SAR86, and SAR11 are reorganized to a greater extent by changes in the environment compared to specialists and contribute more strongly to determining overall biogeographical patterns of marine bacterial communities.
海洋微生物呈现出与物质和能量通量相关的生物地理格局。然而，对于跨时间尺度塑造浮游细菌群落组装的机制，我们的了解仍然有限。我们研究了从波罗的海断面获取的浮游细菌16S rRNA基因片段，以确定系统发育相关性以及与生态位宽度相关的组装过程。群落随时间推移在系统发育上比随机预期的更具相关性，尽管存在相当大的时间变化。因此，在夏季，栖息地过滤（即当地环境条件）而非竞争构建了浮游细菌群落结构，而在春季或秋季并非如此。物种分选（SS）是主要的组装过程，但观察到机制存在时间和分类学上的变化。对于5月的群落，蓝细菌、放线菌、α-和β-变形菌表现出物种分选，而拟杆菌和疣微菌则通过物种分选和质量效应进行组装。同时，γ-变形菌通过中性模型和斑块动态进行组装。栖息地过滤和扩散的时间变化突出了季节性驱动的微生物群落重组的影响。波罗的海典型的丰富种群，如NS3a海洋类群（拟杆菌）以及SAR86和SAR11进化枝具有最高的生态位宽度。疣微菌种群也表现出较高的生态位宽度。令人惊讶的是，浮游细菌群落组成的变化受环境因素调节，这适用于广适类群而非特化类群。我们的结果表明，与特化类群相比，NS3a、SAR86和SAR11等广适类群在更大程度上因环境变化而重组，并且对确定海洋细菌群落的整体生物地理格局贡献更大。
