Groupe de Recherche Interuniversitaire en Limnologie (GRIL), Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, QC, Canada.
ISME J. 2022 Apr;16(4):937-947. doi: 10.1038/s41396-021-01146-y. Epub 2021 Nov 2.
During transit from soils to the ocean, microbial communities are modified and re-assembled, generating complex patterns of ecological succession. The potential effect of upstream assembly on downstream microbial community composition is seldom considered within aquatic networks. Here, we reconstructed the microbial succession along a land-freshwater-estuary continuum within La Romaine river watershed in Northeastern Canada. We captured hydrological seasonality and differentiated the total and reactive community by sequencing both 16 S rRNA genes and transcripts. By examining how DNA- and RNA-based assemblages diverge and converge along the continuum, we inferred temporal shifts in the relative importance of assembly processes, with mass effects dominant in spring, and species selection becoming stronger in summer. The location of strongest selection within the network differed between seasons, suggesting that selection hotspots shift depending on hydrological conditions. The unreactive fraction (no/minor RNA contribution) was composed of taxa with diverse potential origins along the whole aquatic network, while the majority of the reactive pool (major RNA contribution) could be traced to soil/soilwater-derived taxa, which were distributed along the entire rank-abundance curve. Overall, our findings highlight the importance of considering upstream history, hydrological seasonality and the reactive microbial fraction to fully understand microbial community assembly on a network scale.
在从土壤到海洋的运输过程中，微生物群落被改变和重新组装，产生了复杂的生态演替模式。在水生网络中，很少考虑上游组装对下游微生物群落组成的潜在影响。在这里，我们在加拿大东北部拉罗马讷河流域重建了沿陆地-淡水-河口连续体的微生物演替。我们捕捉到了水文季节性，并通过对 16S rRNA 基因和转录本进行测序来区分总群落和反应性群落。通过检查 DNA 和基于 RNA 的组合体如何沿着连续体分歧和收敛，我们推断出组装过程相对重要性的时间变化，春季以质量效应为主，夏季以物种选择为主。网络中最强选择的位置因季节而异，这表明选择热点取决于水文条件而发生变化。无反应部分（无/少量 RNA 贡献）由沿整个水生网络具有不同潜在起源的分类群组成，而大部分反应性池（主要 RNA 贡献）可追溯到土壤/土壤水衍生的分类群，这些分类群沿整个丰度-多度曲线分布。总的来说，我们的研究结果强调了考虑上游历史、水文季节性和反应性微生物部分对于在网络尺度上充分理解微生物群落组装的重要性。
