Data_Sheet_1_Discordant patterns between nitrogen-cycling functional traits and taxa in distant coastal sediments reveal important community assembly mechanisms.docx

A central question in microbial ecology is how immense microbes are assembled in changing natural environments while executing critical ecosystem functions. Over the past decade, effort has been made to unravel the contribution of stochasticity and determinism to the compositional of microbial communities. However, most studies focus on microbial taxa, ignoring the importance of functional traits. By employing shotgun metagenomic sequencing and state-of-the-art bioinformatics approaches, this study comprehensively investigated the microbially mediated nitrogen (N) cycling processes in two geographically distant coastal locations. Both shotgun and 16S rRNA gene amplicon sequencing demonstrated significantly differed taxonomic compositions between the two sites. The relative abundance of major microbial phyla, such as Pseudomonadota, Thaumarchaeota, and Bacteroidota, significantly differed. In contrast, high homogeneity was observed for N-cycling functional traits. Statistical analyses suggested that N-cycling taxonomic groups were more related to geographic distance, whereas microbial functional traits were more influenced by environmental factors. Multiple community assembly models demonstrated that determinism strongly governed the microbial N-cycling functional traits, whereas their carrying taxonomic groups were highly stochastic. Such discordant patterns between N-cycling functional traits and taxa demonstrated an important mechanism in microbial ecology in which essential ecosystem functions are stably maintained despite geographic distance and stochastic community assembly.

微生物生态学领域中的一个核心问题在于，微生物如何在不断变化的自然环境中被大规模组装，并执行关键的生态系统功能。在过去十年中，学者们致力于揭示随机性和确定性对微生物群落组成所做出的贡献。然而，大多数研究聚焦于微生物分类单元，而忽视了功能特征的至关重要性。本研究通过采用枪式宏基因组测序和最先进的生物信息学方法，全面调查了两个地理位置相隔甚远的沿海地区中微生物介导的氮（N）循环过程。枪式测序和16S rRNA基因扩增子测序均显示，两个地点之间的分类组成存在显著差异。主要微生物门类，如假单胞菌门、古菌门和拟杆菌门，其相对丰度存在显著差异。相反，氮循环功能特征表现出高度的均质性。统计分析表明，氮循环分类单元与地理距离的相关性更强，而微生物功能特征则更多受到环境因素的影响。多个群落组装模型表明，确定性强烈地支配了微生物氮循环功能特征，而其携带的分类单元则表现出高度的不确定性。这种氮循环功能特征与分类单元之间的不一致模式，揭示了微生物生态学中的一个重要机制，即在地理距离和随机群落组装的影响下，关键的生态系统功能得以稳定维持。