Institute of Marine Science and Technology, Shandong Universitygrid.27255.37, Qingdao, China.
Joint Lab for Ocean Research and Education at Dalhousie University, Shandong Universitygrid.27255.37 and Xiamen Universitygrid.12955.3a, Qingdao, China.
mBio. 2022 Apr 26;13(2):e0383221. doi: 10.1128/mbio.03832-21. Epub 2022 Mar 14.
Microorganisms drive much of the marine nitrogen (N) cycle, which jointly controls the primary production in the global ocean. However, our understanding of the microbial communities driving the global ocean N cycle remains fragmented. Focusing on "who is doing what, where, and how?", this study draws a clear picture describing the global biogeography of marine N-cycling microbial communities by utilizing the Oceans shotgun metagenomes. The marine N-cycling communities are highly variable taxonomically but relatively even at the functional trait level, showing clear functional redundancy properties. The functional traits and taxonomic groups are shaped by the same set of geo-environmental factors, among which, depth is the major factor impacting marine N-cycling communities, differentiating mesopelagic from epipelagic communities. Latitudinal diversity gradients and distance-decay relationships are observed for taxonomic groups, but rarely or weakly for functional traits. The composition of functional traits is strongly deterministic as revealed by null model analysis, while a higher degree of stochasticity is observed for taxonomic composition. Integrating multiple lines of evidence, in addition to drawing a biogeographic picture of marine N-cycling communities, this study also demonstrated an essential microbial ecological theory-determinism governs the assembly of microbial communities performing essential biogeochemical processes; the environment selects functional traits rather than taxonomic groups; functional redundancy underlies stochastic taxonomic community assembly. A critical question in microbial ecology is how the complex microbial communities are formed in natural ecosystems with the existence of thousands different species, thereby performing essential ecosystem functions and maintaining ecosystem stability. Previous studies disentangling the community assembly mechanisms mainly focus on microbial taxa, ignoring the functional traits they carry. By anchoring microbial functional traits and their carrying taxonomic groups involved in nitrogen cycling processes, this study demonstrated an important mechanism associated with the complex microbial community assembly. Evidence shows that the environment selects functional traits rather than taxonomic groups, and functional redundancy underlies stochastic taxonomic community assembly. This study is expected to provide valuable mechanistic insights into the complex microbial community assembly in both natural and artificial ecosystems.
微生物驱动着海洋氮（N）循环的大部分过程，而氮循环共同控制着全球海洋的初级生产力。然而，我们对驱动全球海洋 N 循环的微生物群落的理解仍然很零散。本研究聚焦于“谁在做什么、在哪里做以及怎么做？”，通过利用海洋 shotgun 宏基因组，清晰地描绘了海洋 N 循环微生物群落的全球生物地理学图景。海洋 N 循环群落在分类上变化很大，但在功能特征水平上相对均匀，表现出明显的功能冗余特性。功能特征和分类群受到相同的一套地理环境因素的影响，其中深度是影响海洋 N 循环群落的主要因素，将中层带与上层带区分开来。分类群表现出纬度多样性梯度和距离衰减关系，但功能特征很少或几乎没有。功能特征的组成通过零模型分析显示出强烈的确定性，而分类组成则表现出更高的随机性。除了描绘海洋 N 循环群落的生物地理图景外，本研究还整合了多种证据，证明了一个重要的微生物生态学理论——确定性支配着执行重要生物地球化学过程的微生物群落的组装；环境选择功能特征而不是分类群；功能冗余是随机分类社区组装的基础。微生物生态学中的一个关键问题是，在存在数千种不同物种的自然生态系统中，复杂的微生物群落是如何形成的，从而执行必要的生态系统功能并维持生态系统的稳定性。以前的研究主要集中在微生物分类群上，以解开群落组装机制，而忽略了它们所携带的功能特征。本研究通过将参与氮循环过程的微生物功能特征及其携带的分类群固定下来，证明了与复杂微生物群落组装相关的一个重要机制。有证据表明，环境选择功能特征而不是分类群，功能冗余是随机分类社区组装的基础。本研究有望为自然和人工生态系统中复杂微生物群落的组装提供有价值的机制见解。
