VBNC状态溶藻菌复苏机制研究

Cyanobacterial blooms are increasingly implicated in water quality problems in freshwater lakes and reservoirs around the world. Lots of studies have focused on the factors that trigger the onset of a cyanobacterial bloom, few have attempted to elucidate the mechanism of bloom decline. The bloom termination process normally takes only one or two days, it is difficult to imagine environmental factors changing markedly over such a short time. More recent studies have shown that changes of population dynamic and culturability of algae-lysing bacteria are closely related with cyanobacterial bloom. Similar trend was also observed by applicant in the lab that the ratio of VBNC (viable but non-culturable) state algae-lysing bacteria varied during different growth phases of co-cultured cyanobacteria. All these findings indicated that VBNC state transformation of algae-lysing bacteria may play an important role in the termination of cyanobacterial bloom. The main focus of this proposed research is the characterization and comparative analysis of the VBNC state transformation of algae-lysing bacterial isolates. Combination of biotic and abiotic factors will be tested in the lab to induce VBNC state of bacterial cells or resuscitate them into culturable. This study will provide insight into the cyanobacteria-bacteria interaction during cyanobacterial bloom termination and help developing a tool to prevent and control the bloom.

淡水水体中蓝藻水华对水质的影响已成为全球普遍面临的环境问题，目前对影响水华产生的因素已有大量研究，而对水华消亡的过程和引起消亡的原因所知相对较少。由于水华的消亡非常迅速，仅用环境因素的改变难以解释这一现象。近年来多项研究发现水体中的细菌，尤其是与蓝藻密切相关的溶藻菌在水华消亡过程中有数量，种群结构及可培养性的变化，申请者前期研究也在实验室观察到了与蓝藻共培养的溶藻菌其VBNC（活的不可培养状态）比例在不同生长期有较大的改变，因此溶藻菌的活性变换可能是影响蓝藻水华消亡的关键因素之一。本项目中申请者拟通过研究水华中分离出的多个溶藻菌株的VBNC状态变换规律，找出促使VBNC状态溶藻菌复苏的环境和生物因素，对自然界蓝藻水华消亡过程中溶藻菌的活性变化及藻菌关系进行深入研究，以揭示水华生消过程的深层机制，为制定有效的预测与防治水华的生物控制手段提供基础。

有害藻华的产生和消亡常常伴随着细菌数量和种群结构的变动，以往的研究中对细菌活性的变化及其VBNC状态转换在藻华生消过程中的作用所知甚少。本项目提出溶藻菌的活性变换是藻华消亡的关键因素的假说，对藻华中分离出的多个溶藻菌进行了VBNC状态变化特征的比较研究。研究结果基本验证了假说，发现了不同溶藻菌对水华蓝藻铜绿微囊藻（Microcystis aeruginosa）的杀灭机理存在差异，可能在藻华生消不同时期起作用并有协同效应；蓝藻细胞及其毒素对溶藻菌的VBNC状态变化有直接影响，并存在作用阈值和种属特异性；VBNC状态溶藻菌的休眠和复苏过程伴随着形态、溶藻能力和脂肪酸组成等一系列生理生化的变化，并发现菌-藻共培养系统中60% 左右的VBNC比例是二者相互作用下的稳态，而水华的爆发与消亡都是这一稳态的偏移。