海洋细菌Hahella sp. KA22对赤潮异弯藻的杀藻机制研究

Marine bacteria play great roles in the process of harmful algal blooms (HABs), especially bacteria with anti-algal capability. Algicidal bacteria are important for controlling HABs, and the mechanism of algicidal functional bacterium toward HABs-causing algae has drawn more attentions recently. In our previous study, a novel algicidal bacterium Hahella sp. KA22 being capable of producing an algicidal pigment was isolated from marine environment, where HABs were detected. The algicidal bacterium also could produce quorum sensing signaling molecule. Although it was acknowledged that pigments produced by marine bacteria could kill HABs-causing microalgae and quorum sensing might involve into the production of these pigments, more works should be conducted to reveal the mechanism of killing microalgae by pigments and function of quorom sensing in the process of controlling HABs. In this proposal, the HABs-causing algae, Heterosigma akashiwo and the functional bacterium Hahella sp. KA22 are going to be used as model organisms to reveal these questions. By analyzing the construction of the algicidal pigment, its way and conditions of killing H. akashiwo and its synthetic pathway, the mechanism of its algicidal function is going to be detected. Further, combing verification experiments in mesocosm, quorom sensing signalling moleculars and their inhibitors are going to be used for demonstrating how quorom sensing control the bloom of H. akashiwo. Based on studies on molecular level and community leveal, we are trying to reveal the algicidal mechanism of functional bacterium Hahella sp. KA22 towards the HABs-causing microalgae H. akashiwo. This study will deepen our understanding and provide insights into mechanism of controlling HABs by functional bacterium.

海洋细菌在赤潮生消过程中起着重要作用，特别是杀藻菌，是赤潮生物防治中的最主要力量，其杀藻机制是研究的重要环节。在前期研究中，申请人从赤潮爆发原位环境分离到一株产杀藻色素的高效杀藻菌Hahella sp. KA22，该菌能够产生群体感应信号分子。虽然已有研究表明海洋细菌所产色素具有杀藻功能且其产生多与群体感应有关，但是关于色素杀藻机理及群体感应如何参与赤潮消亡的调控还有待深入研究。本项目基于前期研究基础，以赤潮异弯藻和杀藻菌KA22为研究对象，通过对杀藻色素结构、合成途径及作用方式研究，从分子水平揭示功能菌的杀藻机理；并基于群体感应基因分析、群体感应对杀藻色素及藻菌生物量影响的研究、结合中宇宙培养验证，探明群体感应对赤潮藻消亡的调控作用。结合分子水平及群体水平研究，最终阐释杀藻菌KA22对赤潮异弯藻的杀藻机制，从而深化对杀藻菌调控赤潮消亡机制的认识，为有效利用功能菌防治赤潮提供理论依据。

海洋细菌在赤潮生消过程中起着重要作用，特别是杀藻菌，是赤潮生物防治中的最主要力量，其杀藻机制是研究的重要环节。本项目针对前期从赤潮爆发原位环境中分离到一株产抑藻色素的高效杀藻菌Hahella sp. KA22，从杀藻菌合成杀藻物质的途径和机制、赤潮藻的死亡机制等方面展开研究，揭示了其对赤潮异弯藻的杀藻机制。取得的具体结果如下：.我们首先从杀藻菌KA22的角度开展研究，获得了杀藻菌KA22中的杀藻活性物质—灵菌红素；通过对其基因组测序和分析，明晰了灵菌红素合成的过程；结合基因组学、转录组学及网络分析的方法，我们对菌株 KA22产灵菌红素的基因簇表达以及调控模型进行研究，发现灵菌红素合成不受群体感应效应分子的调控，其基因簇合成调控十分复杂，不仅受到ChrR、RpoE的直接调控，还能够受到全局调控因子c-di-GMP的间接调控；.然后，从藻的生理生化指标的变化角度，通过研究灵菌红素杀灭赤潮异弯藻过程中藻细胞形态结构、生理生化酶活、光合效率及基因表达的响应过程，探明了灵菌红素杀灭藻细胞的机制，即灵菌红素胁迫导致藻细胞内容物和线粒体、叶绿体等主要细胞器裂解，核结构弥散，细胞膜通透性增大；同时细胞内活性氧自由基 (ROS)过量累积，造成光合作用相关基因psbA和rbcS的基因转录水平的明显下调，最终引起藻细胞死亡；.进一步，从氧化应激和细胞死亡调控的角度，明确了杀藻菌对赤潮异弯藻生理和生化代谢的限制作用，揭示了赤潮异弯藻细胞内响应杀藻信号的氧化应激反应、细胞程序化死亡以及物质代谢相关基因的调控机制。在转录组学分析的基础上，解析了微藻细胞内ROS分子产生与积累相关基因转录水平的变化，阐明了与ROS信号有关的胁迫适应与细胞程序化死亡诱导的分子调控机理；.最后，通过构建赤潮藻稳定培养体系，逐级扩大培养的方式，我们初步阐明了其在赤潮生消调控的动力学过程。.通过上述研究，我们明晰了海洋细菌Hahella sp. KA22对赤潮异弯藻的杀藻机制，为有效利用功能菌防治赤潮提供理论依据。