溶藻细菌的筛选及群体感应信号对其活力的调节作用

Screening the algicidal bacteria from phycosphere environment and evaluate their algicidal activity under quorum sensing regulation

为了开发微生物控藻技术,从藻际环境中分离了具有溶藻活力(algicidal ability)的细菌,并探讨了群体感应信号对溶藻活力的调节作用。通过稀释涂布法从甲藻赤潮样品中分离得到了10株溶藻细菌,16S rRNA基因序列鉴定为5个属,包括交替假单胞菌(Pseudoalteromonas sp.)、假单胞菌(Pseudomonas sp.)、弧菌属(Vibrio sp.)、新鞘氨醇杆菌属(Novosphingobium sp.)以及鞘氨醇单胞菌(Sphingomonas sp.)。溶藻能力分析显示,这10株细菌均具有较强的溶藻能力,对裸甲藻叶绿素的产生具有明显的抑制能力,其中尤以新鞘氨醇杆菌最为突出。薄层色谱法TLC检测到8株细菌具有产群体感应信号的能力,信号分子主要为高丝氨酸内酯AHL C8、AHL C8 O以及AHL 10。为了验证群体感应信号对溶藻能力的调节作用,以新鞘氨醇杆菌为代表构建了AHL突变株,通过突变株与野生株的比较试验,发现AHL的缺失明显降低了溶藻能力,证实抑藻能力受到AHL信号的正向调节。酶活分析显示主要的抑制机制在于诱发了藻类明显的氧化应激,致使丙二醛(MDA)含量和超氧化物歧化酶(SOD)活力明显上升。考虑到藻类的有效防控是水生生态安全的重要组成部分,本研究结果提示微生物利用群体感应信号介导溶藻作用,可能帮助我们开发针对性的方法提升控制藻类的能力,例如合成生物学技术的引入。

In order to develop algal-control technology based on microbial methods,a variety of algicidal bacteria were isolated from phycosphere,and their algicidal activities were investigated,along with the effect from the regulation of quorum sensing signal.Firstly,the 16S rRNA gene sequences of ten algicidal bacteria,which were isolated from dinoflagellate algal-bloom samples according to dilution coating method,showed their identities as Pseudoalteromonas sp.,Pseudomonas sp.,Novosphingobium sp.,Sphingomonas sp.and two strains of Vibrio sp.Secondly,these 10 strains displayed relatively strong algicidal ability and could significantly inhibit the production of chlorophyll a by Gymnodinium sp.,especially Novosphingobium sp.Based on TLC results,8 strains of bacteria demonstrated the ability to produce quorum sensing signals,mainly with acyl-homoserine lactone(AHL)C8-,C8-O-and C10-AHL as signal molecules.Thirdly,the regulatory effect of quorum sensing signal on algicidal ability was confirmed through the comparative tests between mutant and wild strains.For example,the lack of AHL in Novoshingobium sp.caused significant decrease of the algal dissolving ability,indicating the algae inhibition was positively regulated by AHL signal.Further analysis showed the possible mechanism came from the induction of algal ROS stress,which led to the significant increase of MDA and SOD enzymatic activities.As the effective prevention and control of algae is very important for aquatic ecological security,the mediation of algal lysis by microorganisms through quorum sensing signals may be applicable for the development of targeted methods to improve the controllability of algae,such as the introduction of synthetic biology technology.