Smets Wenke, Spada Lucia Maria, Gandolfi Isabella, Wuyts Karen, Legein Marie, Muyshondt Babette, Samson Roeland, Franzetti Andrea, Lebeer Sarah
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA.
Department of Bioscience Engineering, University of Antwerpgrid.5284.b, Antwerp, Belgium.
Microbiol Spectr. 2022 Apr 27;10(2):e0242021. doi: 10.1128/spectrum.02420-21. Epub 2022 Mar 2.
Every year, deciduous trees shed their leaves, and when new leaves emerge next spring, they establish a characteristic bacterial leaf community. In this exploratory study, we assessed the bacterial phyllosphere (aboveground plant surfaces) of eight London plane trees () in Antwerp and Milan by sampling weekly during leaf emergence and expansion. We sampled the surfaces of different tree compartments: leaves, leaf buds, branches, and trunk, for up to 6 weeks. Phyllosphere community composition was most strongly determined by tree compartment. Only the communities on the emerging leaves showed changing dynamics over time. The rate of change in the leaf phyllosphere composition, expressed as the beta dissimilarity between consecutive time points, was very high following leaf emergence, with decreasing speed over time, indicating that these communities stabilize over time. We also identified cooccurring groups of bacteria associated with potential stages of ecological succession on the leaves and accordingly named them general cluster, early cluster, middle cluster, and late cluster. Taxa of the general cluster were not only more abundant than the others on leaves, but they were also widespread on other tree compartments. The late cluster was most pronounced in trees surrounded by trafficked urban land use. This study mainly generates hypotheses on the ecological succession on the emerging leaves of deciduous trees in urban environments and contributes to understanding the development of the tree leaf phyllosphere in spring. Improving our understanding of phyllosphere ecology is key in successfully applying bacterial biological agents or modulating the leaf microbiome in order to achieve valuable ecosystem services, such as plant protection, plant growth, air purification, and developing a healthy human immune system. Modulation of the phyllosphere microbiome in the field works only with variable success. To improve the impact of our applications in the field, a better understanding of the ecological principles governing phyllosphere dynamics is required. This exploratory study demonstrates how the combination of different analyses of a chronosequence of bacterial communities can provide new ecological insights. With a limited number of sampled trees, we demonstrated different indications of ecological succession of bacterial communities in the leaves and observed a potential impact of intensely trafficked land use becoming apparent in the leaf bacterial communities approximately 3 weeks after leaf emergence, consisting of a separate stage in community development.
每年，落叶树都会落叶，当来年春天新叶长出时，它们会形成一个具有特征的叶片细菌群落。在这项探索性研究中，我们通过在叶片长出和扩展期间每周采样，评估了安特卫普和米兰的八棵悬铃木的细菌叶际（地上植物表面）。我们对不同的树体部分进行采样：树叶、叶芽、树枝和树干，采样时间长达6周。叶际群落组成受树体部分的影响最大。只有新长出叶子上的群落显示出随时间变化的动态。叶际组成的变化率，以连续时间点之间的β差异表示，在叶子长出后非常高，随着时间推移速度降低，表明这些群落随时间趋于稳定。我们还确定了与叶片上生态演替潜在阶段相关的共现细菌群，并相应地将它们命名为通用簇、早期簇、中期簇和晚期簇。通用簇的分类群不仅在叶子上比其他分类群更丰富，而且在其他树体部分也广泛存在。晚期簇在被交通繁忙的城市土地利用环绕的树木中最为明显。本研究主要提出了关于城市环境中落叶树新长出叶子上生态演替的假设，并有助于理解春季树叶叶际的发育。更好地理解叶际生态学是成功应用细菌生物制剂或调节叶片微生物组以实现有价值的生态系统服务（如植物保护、植物生长、空气净化和发展健康的人类免疫系统）的关键。在田间对叶际微生物组的调节效果参差不齐。为了提高我们在田间应用的效果，需要更好地理解控制叶际动态的生态原理。这项探索性研究展示了对细菌群落时间序列进行不同分析如何能提供新的生态见解。通过对数量有限的采样树木进行研究，我们展示了叶片中细菌群落生态演替的不同迹象，并观察到交通繁忙的土地利用在叶片长出约3周后对叶片细菌群落产生的潜在影响，这构成了群落发展中的一个单独阶段。
