Wang Miao, Veldsink Jan Henk, Dini-Andreote Francisco, Salles Joana Falcão
Research Group of Microbial Community Ecology, Genomics Research in Ecology and Evolution in Nature, Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747AG, Groningen, The Netherlands.
Antonie Van Leeuwenhoek. 2018 Nov;111(11):2061-2078. doi: 10.1007/s10482-018-1098-5. Epub 2018 May 30.
Disentangling the relative influences of soil properties and plant-host on root-associated microbiomes in natural systems is challenging, given that spatially segregated soil types display distinct historical legacies. In addition, distant locations may also lead to biogeographical patterns of microbial communities. Here, we used an undisturbed salt marsh chronosequence spanning over a century of ecosystem development to investigate changes in the community composition and abundance of a set of nitrogen-cycling genes. Specifically, we targeted genes of diazotrophs and ammonia oxidizers associated with the bulk and rhizosphere soil of the plant species Limonium vulgare. Samples were collected across five distinct successional stages of the chronosequence (ranging from 5 to 105 years) at two time-points. Our results indicate that soil variables such as sand:silt:clay % content and pH strongly relates to the abundance of N-cycling genes in the bulk soil. However, in the rhizosphere samples, the abundance of ammonia-oxidizing organisms (both bacteria and archaea, AOB and AOA, respectively) was relatively constant across most of the successional stages, albeit displaying seasonal variation. This result indicates a potentially stronger control of plant host (rather than soil) on the abundance of these organisms. Interestingly, the plant host did not have a significant effect on the composition of AOA and AOB communities, being mostly divergent according to soil successional stages. The abundance of diazotrophic communities in rhizosphere samples was more affected by seasonality than those of bulk soil. Moreover, the abundance pattern of diazotrophs in the rhizosphere related to the systematic increase of plant biomass and soil organic matter along the successional gradient. These results suggest a potential season-dependent regulation of diazotrophs exerted by the plant host. Overall, this study contributes to a better understanding of how the natural formation of a soil and host plants influence the compositional and abundance changes of nitrogen-cycling genes in bulk and rhizosphere soil microhabitats.
在自然系统中，区分土壤性质和植物宿主对根际微生物群落的相对影响具有挑战性，因为空间上隔离的土壤类型具有不同的历史遗留特征。此外，不同的地理位置也可能导致微生物群落的生物地理模式。在这里，我们利用一个跨越一个多世纪生态系统发展的未受干扰的盐沼时间序列，来研究一组氮循环基因的群落组成和丰度变化。具体来说，我们针对与植物物种补血草的根际土壤和非根际土壤相关的固氮菌和氨氧化菌的基因。在两个时间点，跨越时间序列的五个不同演替阶段（从5年到105年）采集样本。我们的结果表明，诸如砂:粉砂:黏土百分比含量和pH值等土壤变量与非根际土壤中氮循环基因的丰度密切相关。然而，在根际样本中，氨氧化生物（分别为细菌和古菌，即氨氧化细菌和氨氧化古菌）的丰度在大多数演替阶段相对恒定，尽管存在季节性变化。这一结果表明植物宿主（而非土壤）对这些生物的丰度可能具有更强的控制作用。有趣的是，植物宿主对氨氧化古菌和氨氧化细菌群落的组成没有显著影响，这些群落主要根据土壤演替阶段而有所不同。根际样本中固氮群落的丰度比非根际土壤受季节性影响更大。此外，根际中固氮菌的丰度模式与沿演替梯度植物生物量和土壤有机质的系统性增加有关。这些结果表明植物宿主可能对固氮菌有季节依赖性调控。总体而言，本研究有助于更好地理解土壤和宿主植物的自然形成如何影响非根际和根际土壤微生境中氮循环基因的组成和丰度变化。
