DMSP诱导微藻共栖细菌群体感应启动抑藻活性的研究

The interaction between algae and bacteria is the focus of investigating the relationship among species of marine communities. Quorum sensing (QS) regulates chemical signals and also influences the ecological balance in the phycosphere. DMSP is widely acknowledged as an intermediate in the interaction between algae and bacteria. DMSP and its degradation substances are related to the metabolic pathways of algae and bacteria. DMSP can induce bacteria to produce AHLs, but its influence on the interaction between algae and bacteria has been rarely studied. DMSP and its degradation substances could be a transboundary signal between algae and bacteria and can induce the initiation of the microalgae-associated bacteria with QS system to inhibit microalgal growth. This project will analyze the induction effect of QS system startup from cell, biochemistry and molecular level by detecting the AHLs, algicidal activity, differential metabolites and transcriptome analysis in Ponticoccus sp. PD-2 by DMSP and its degradation substances. The mechanism of DMSP as the intermediate in the QS system was analyzed to adjust the number of microalgae. This study will not only deepen our understanding of the role of DMSP in the interaction between algae and bacteria but will also provide the scientific basis for maintaining the ecological balance of the microenvironment.

藻菌相互作用是海洋生物群落种间关系的研究热点，细菌群体感应(QS)作为化学信号介导的调节方式对藻际微环境的生态平衡具有重要作用。DMSP是藻菌交互作用中被广泛认可的中间体，其产生和降解过程与藻菌间的代谢途径具有密切联系。研究表明DMSP可诱导细菌产生AHLs，但对其影响藻菌交互作用的研究却知之甚少。我们推测DMSP及其降解产物可能是一种藻菌间跨界信号，诱导微藻共栖细菌QS系统启动，使之行使抑藻功能。为证明该设想，本项目以微藻共栖细菌PD-2为研究对象，研究DMSP及其降解产物外加诱导对其AHLs产生及抑藻活性的影响，同时通过差异代谢物检测以及转录组学分析，分别从细胞、生化和基因三个层面证实DMSP对微藻共栖细菌QS系统启动的诱导作用，解析DMSP介导的群体感应系统调节微藻数量的作用机制。该研究不仅将加深对DMSP在藻菌相互关系中作用的认识，还可为藻际微环境的生态平衡维持机制提供科学依据。

藻菌相互作用是海洋生物群落种间关系的研究热点，细菌群体感应（Quorum Sensing, QS）作为化学信号介导的调节方式对藻际微环境的生态平衡具有重要作用。如能更为清楚的了解微藻共栖细菌QS的调控功能及作用方式，将为深入认识赤潮爆发过程中微藻优势种的演替及其生消过程提供更加充分的依据。本项目选择海洋玫瑰杆菌这一海洋微藻共栖细菌中的主体类群和QS细菌关键种类，从分子和基因水平解析存在的QS，探明该类细菌QS调控功能及其对共栖藻的影响。研究结果显示，从典型赤潮藻中分离出842株微藻共栖细菌，其中113株（13.42 %）为QS细菌。这些QS菌主要属于Sulfitobacter，Ponticoccus，Leisingera和Nitratireductor，且90%是玫瑰杆菌。它们具有成膜、降解DMSP和促进或抑制藻类生长的藻菌作用相关的生态学功能。通过全基因组测序，从PD-2中发现了AHLs合成基因，敲除luxI同源基因后的PD-2不再产生AHLs信号分子，同时对三株赤潮藻（东海原甲藻、球形棕囊藻和塔玛亚历山大藻）均不表现出抑藻作用，说明群体感应调控该菌的抑藻活性；研究了PD-2细菌生长过程中AHLs含量变化，结果发现AHLs在细菌生长后期有降解现象，这说明PD-2细菌自体可能存在降解AHLs的蛋白酶，在生长后期随着酶含量累积，产生降解AHLs的效果。