近岸微生物群落演替特征对浓缩溶解有机质添加的响应

Responses of coastal microbial communities to addition of concentrated dissolved organic matter

摘要:

海洋中的溶解有机质(dissolved organic matter, DOM)成分复杂、来源多样，异养细菌作为DOM的主要分解者也呈现高度的生物多样性，二者之间的相互作用在生物地球化学循环中起着重要作用。截至目前，海洋中DOM的组成与微生物群落之间的相互作用尚不完全清楚。【目的】 探究添加海洋来源的浓缩DOM后微生物群落的动态变化。【方法】 将从近岸海水中富集到>1 kDa的DOM添加至微宇宙培养体系后，分别在不同的培养天数进行Illumina扩增子测序、溶解有机碳(dissolved organic carbon, DOC)浓度监测及异养细菌分离纯化。【结果】 DOM添加导致微生物群落组成发生了明显的演替，且高DOM处理组中微生物群落的变化更明显，在第3、10、30天分别出现弯曲杆菌门(Campylobacterota)、亚硝化球菌目(Nitrosococcales)和栖苏打菌科(Nitrincolaceae)等类群占比的升高。群落的α多样性和均匀度先在0−3 d内降低，而后又在10−30 d内升高，在3−10 d发生变化趋势的转折。网络分析发现，高DOM处理组的网络结构比对照组更加紧密复杂。此外，不同浓度DOM培养体系中分离得到的可培养菌株明显不同，并分离获得了DOM处理组的特有属，它们可能是重要的DOM降解类群。【结论】 浓缩DOM添加引起微宇宙培养体系中微生物群落结构的明显演替，其群落组成可能与DOM成分协同变化，影响着群落的演替方向。不同浓度DOM的培养体系也可能促进了具有不同生存策略的细菌的生长。本研究为更深入地理解微生物对海洋DOM的响应机制提供了理论依据。

Abstract:

Dissolved organic matter (DOM) in the ocean encompasses complex and diverse organic compounds, and heterotrophic bacteria, the main DOM decomposers, also exhibit high biodiversity. The interactions between heterotrophic bacteria and DOM play an important role in biogeochemical cycles, which, however, are not fully understood. [Objective] To explore the dynamics of microbial communities with the addition of marine-derived concentrated DOM. [Methods] DOM with a molecular weight exceeding 1 kDa and enriched from coastal seawater was introduced into microcosm culture systems. Illumina amplicon sequencing, dissolved organic carbon (DOC) concentration measurement, and bacterial isolation were performed on different days of incubation. [Results] The addition of DOM significantly influenced bacterial community composition, inducing more pronounced changes in the high-DOM group. Specifically, the relative abundance of Campylobacterota, Nitrosococcales, and Nitrincolaceae increased in the high-DOM group on days 3, 10, and 30, respectively. The alpha diversity and evenness of the microbial community decreased during days 0−3 and increased during days 10−30, with a transition point occurring between days 3 and 10. The network analysis revealed that the high-DOM group exhibited a more tightly interconnected and complex network than the control group. In addition, bacterial isolates from the culture systems added with different concentrations of DOM were distinct. The specific genera of different DOM treatments were identified, which may be key groups in DOM degradation. [Conclusion] The addition of DOM triggers the succession of microbial community structures within microcosm culture systems, and the community composition may be associated with specific DOM components, which influence the direction of community succession. Furthermore, the varying DOM concentrations select for culturable bacteria with diverse survival strategies. This study provides a basis for enriching our understanding about the mechanisms underlying microbial responses to marine-derived DOM.