State Key Laboratory of Cellular Stress Biology, and School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, PR China.
State Key Laboratory of Cellular Stress Biology, and School of Life Sciences, Xiamen University, Xiamen, Fujian, 361102, PR China; Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Xiamen University, Xiamen, Fujian, 361102, PR China.
Environ Pollut. 2020 Aug;263(Pt A):114475. doi: 10.1016/j.envpol.2020.114475. Epub 2020 Apr 1.
Sulfitobacter porphyrae ZFX1, isolated from surface seawater of the East China Sea during a Prorocentrum donghaiense bloom recession, exhibits high algicidal activity against P. donghaiense. To evaluate the algicidal effect of ZFX1, the algicidal mode and stability were investigated. The results showed that ZFX1 indirectly attacked algae by secreting algicidal compounds, and the algicidal activity of the ZFX1 supernatant was insensitive to different temperatures, light intensities and pH values (pH 3-12). To explore the algicidal mechanism of the ZFX1 supernatant, its effects on the morphological and ultrastructural alterations, photosynthetic capacity, reactive oxygen species (ROS) and antioxidative system of P. donghaiense were investigated. Scanning and transmission electron microscopy revealed that the ZFX1 supernatant destroyed the algal cell membrane structure and caused intracellular leakage. The decrease in the chlorophyll a content and the marked declines in both the photosynthetic efficiency (Fv/Fm) and the electron transport rate (rETR) indicated that the ZFX1 supernatant could damage the photosynthetic system of P. donghaiense. The excessive production of ROS in algal cells demonstrated the oxidative damage triggered by the ZFX1 supernatant. Although the antioxidant defense system of P. donghaiense was activated to scavenge excessive ROS, lipid oxidation occurred. The fatty acid composition profile indicated that the ZFX1 supernatant markedly increased the contents of two saturated fatty acids and a monounsaturated fatty acid and decreased the proportion of two polyunsaturated fatty acids, which resulted in lipids with a lower degree of unsaturation (DU). The decline in the DU decreased the lipid fluidity and rigidified the membrane system, and these effects destroyed the function of the membrane system and ultimately resulted in algal cell death. Therefore, ZFX1 probably plays a key role in mitigating P. donghaiense bloom by inducing lipid oxidation, decreasing the DU of lipids and ultimately destroying the membrane systems of algal cells.
从东海赤潮衰退期间的东海表层海水中分离到的一株硫杆菌（Sulfitobacter porphyrae ZFX1）对东海原甲藻（Prorocentrum donghaiense）具有很高的杀藻活性。为了评估 ZFX1 的杀藻效果，研究了其杀藻模式和稳定性。结果表明，ZFX1 通过分泌杀藻化合物间接攻击藻类，ZFX1 上清液的杀藻活性对不同温度、光照强度和 pH 值（pH 3-12）不敏感。为了探索 ZFX1 上清液的杀藻机制，研究了其对东海原甲藻形态和超微结构变化、光合能力、活性氧（ROS）和抗氧化系统的影响。扫描和透射电子显微镜显示，ZFX1 上清液破坏了藻类细胞膜结构，导致细胞内物质泄漏。叶绿素 a 含量的降低以及光合效率（Fv/Fm）和电子传递速率（rETR）的显著下降表明，ZFX1 上清液可以破坏东海原甲藻的光合作用系统。藻类细胞中 ROS 的过度产生表明 ZFX1 上清液引发了氧化损伤。尽管东海原甲藻的抗氧化防御系统被激活以清除过量的 ROS，但脂质发生了氧化。脂肪酸组成谱表明，ZFX1 上清液显著增加了两种饱和脂肪酸和一种单不饱和脂肪酸的含量，降低了两种多不饱和脂肪酸的比例，导致脂质的不饱和程度（DU）降低。DU 的下降降低了脂质的流动性并使膜系统僵化，这些影响破坏了膜系统的功能，最终导致藻类细胞死亡。因此，ZFX1 可能通过诱导脂质氧化、降低脂质的 DU 并最终破坏藻类细胞的膜系统，在减轻东海原甲藻赤潮方面发挥关键作用。
