一株溶藻菌 Zobellella sp. B307对太平洋亚历山大藻的溶藻特性及作用机制研究

The Algicidal Characteristics and Mechanism of an Algicidal Bacterium Zobellella sp.B307 on Alexanderium pacificum

为研究溶藻菌对赤潮甲藻的作用机制,本文从胶州湾沉积物中分离得到的一株耐盐菌株Zobellella sp.B307,并研究了该菌株对太平洋亚历山大藻(Alexandrium pacificum)的抑制效果,从细胞结构、生理水平和分子水平探究了该菌株的抑藻途径及作用机制。结果表明,该菌株的抑藻途径为分泌胞外活性物质的间接溶藻,72 h的溶藻率高达91%。溶藻过程中藻细胞壁破损,叶绿素a和总蛋白含量显著下降,藻细胞的活性氧(ROS)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性显著高于对照组,这表明溶藻物质对藻细胞造成的强烈氧化损伤是导致其死亡的直接原因。热休克蛋白基因(HSP)表达量显著上调,说明溶藻物质激发藻细胞产生的ROS在激活抗氧化系统的同时诱导产生HSP70,二者联合清除ROS以减缓藻细胞受应激损伤的程度;A.pacificum的网格蛋白基因(Clathrin)表达量显著上调,表示由网格蛋白介导的胞吞作用明显增强,进而说明为减轻光合营养功能受损造成的影响,藻细胞的异养功能增强。本研究结果有助于诠释菌藻关系,更为探究赤潮治理的生物方法提供重要的理论支持和实践指导。

In order to study the algicidal mechanism of algicidal bacteria on red tide dinoflagellate,a salt-tolerant bacterium Zobellella sp.B307 with algicidal activity to the Alexandrium pacificum was isolated from the sediments of Jiaozhou Bay.To explore the algicidal mechanism of Zobellella sp.B307,we investigated its effect on the cellular structure,physiologyl and molecular mechanism of A.pacificum.The results showed that the inhibition mechanism of the strain was indirect lytic effects causing by extracellular active substances.And after 72 h cultivation with bacterium addition,the algicidal rate reached up to 91%,revealing its strong algicidal activity against A.pacificum.Meanwhile,we observed cell wall damage,chlorophyll-a and total protein contents decrease,and the excessive production of reactive oxygen species(ROS),superoxide dismutase(SOD)and catalase(CAT).It indicated that the serious oxidative damage caused by algae-lysing substances was the direct cause of A.pacificum death.The expression level of heat shock protein(HSP)gene was significantly upregulated,suggesting that algae-lysing substances could induce the production of HSP,and the combined effects of highly expressed HSP and highly activited antioxidant system of A.pacificum could eliminate ROS and alleviate the algae cells damage caused by oxidative stress.In addition,the expression of A.pacificum clathrin gene was significantly upregulated,indicating algae cells could enhanced heterotrophic function to compensate the loss of photosynthesis caused by algae-lysing substances.The results of this study will contribute to explain the newly founded relationship between bacteria and algae,and explore the new biological methods of red tide control.