Table_1_Regional and Microenvironmental Scale Characterization of the Zostera muelleri Seagrass Microbiome.XLSX

Seagrasses are globally distributed marine plants that represent an extremely valuable component of coastal ecosystems. Like terrestrial plants, seagrass productivity and health are likely to be strongly governed by the structure and function of the seagrass microbiome, which will be distributed across a number of discrete microenvironments within the plant, including the phyllosphere, the endosphere and the rhizosphere, all different in physical and chemical conditions. Here we examined patterns in the composition of the microbiome of the seagrass Zostera muelleri, within six plant-associated microenvironments sampled across four different coastal locations in New South Wales, Australia. Amplicon sequencing approaches were used to characterize the diversity and composition of bacterial, microalgal, and fungal microbiomes and ultimately identify “core microbiome” members that were conserved across sampling microenvironments. Discrete populations of bacteria, microalgae and fungi were observed within specific seagrass microenvironments, including the leaves and roots and rhizomes, with “core” taxa found to persist within these microenvironments across geographically disparate sampling sites. Bacterial, microalgal and fungal community profiles were most strongly governed by intrinsic features of the different seagrass microenvironments, whereby microscale differences in community composition were greater than the differences observed between sampling regions. However, our results showed differing strengths of microbial preferences at the plant scale, since this microenvironmental variability was more pronounced for bacteria than it was for microalgae and fungi, suggesting more specific interactions between the bacterial consortia and the seagrass host, and potentially implying a highly specialized coupling between seagrass and bacterial metabolism and ecology. Due to their persistence within a given seagrass microenvironment, across geographically discrete sampling locations, we propose that the identified “core” microbiome members likely play key roles in seagrass physiology as well as the ecology and biogeochemistry of seagrass habitats.

海草是全球分布的海洋植物，是海岸生态系统中极具价值的组成部分。与陆生植物类似，海草的生产力与健康状况很可能在很大程度上由海草微生物组（microbiome）的结构与功能决定，而该微生物组会分布于植物体内多个不同的离散微环境中，包括叶际（phyllosphere）、内生境（endosphere）与根际（rhizosphere）——这些微环境的物理与化学条件均存在差异。本研究针对澳大利亚新南威尔士州4处不同海岸地点采集的穆氏大叶藻（Zostera muelleri）的6种植物相关微环境样本，分析了其微生物组的组成模式。研究采用扩增子测序（amplicon sequencing）技术表征了细菌、微藻与真菌微生物组的多样性与组成，并最终鉴定出在各采样微环境中均保守存在的“核心微生物组（core microbiome）”成员。研究在特定海草微环境（包括叶片、根系与根状茎）中观察到了细菌、微藻与真菌的离散类群，且在地理分布迥异的采样点的这些微环境中，均发现了“核心”类群的存在。细菌、微藻与真菌的群落组成最主要受不同海草微环境的内在特征调控，即群落组成的微尺度差异大于采样区域间的差异。不过，研究结果显示植物尺度下的微生物偏好性存在强度差异：相较于微藻与真菌，细菌的微环境变异更为显著，这表明细菌菌群联合体与海草宿主之间存在更特异性的互作，且可能意味着海草与细菌的代谢及生态学过程之间存在高度特化的耦合关系。由于所鉴定的“核心微生物组”成员在地理分布迥异的采样地点的特定海草微环境中均持续存在，本研究提出，这些核心微生物组成员很可能在海草生理过程以及海草生境的生态学与生物地球化学过程中发挥关键作用。