Nishiguchi Tomoki, Cho Kichul, Yasutomi Masumi, Ueno Mikinori, Yamaguchi Kenichi, Basti Leila, Yamasaki Yasuhiro, Takeshita Satoshi, Kim Daekyung, Oda Tatsuya
Graduate School of Fisheries Science & Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Jeju Center, Korea Basic Science Institute (KBSI), Smart Building 1F, Jeju Science Park, 2170-2, Ara-dong, Jeju-Si, Jeju Special Self-Governing Province 690-756, Republic of Korea; Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea.
Aquat Toxicol. 2016 Oct;179:95-102. doi: 10.1016/j.aquatox.2016.08.019. Epub 2016 Aug 29.
A harmful dinoflagellate, Heterocapsa circularisquama, is highly toxic to shellfish and the zooplankton rotifer Brachionus plicatilis. A previous study found that H. circularisquama has both light-dependent and -independent haemolytic agents, which might be responsible for its toxicity. Detailed analysis of the haemolytic activity of H. circularisquama suggested that light-independent haemolytic activity was mediated mainly through intact cells, whereas light-dependent haemolytic activity was mediated by intracellular agents which can be discharged from ruptured cells. Because H. circularisquama showed similar toxicity to rotifers regardless of the light conditions, and because ultrasonic ruptured H. circularisquama cells showed no significant toxicity to rotifers, it was suggested that live cell-mediated light-independent haemolytic activity is a major factor responsible for the observed toxicity to rotifers. Interestingly, the ultrasonic-ruptured cells of H. circularisquama suppressed their own lethal effect on the rotifers. Analysis of samples of the cell contents (supernatant) and cell fragments (precipitate) prepared from the ruptured H. circularisquama cells indicated that the cell contents contain inhibitors for the light-independent cell-mediated haemolytic activity, toxins affecting H. circularisquama cells themselves, as well as light-dependent haemolytic agents. Ethanol extract prepared from H. circularisquama, which is supposed to contain a porphyrin derivative that displays photosensitising haemolytic activity, showed potent toxicity to Chattonella marina, Chattonella antiqua, and Karenia mikimotoi, as well as to H. circularisquama at the concentration range at which no significant toxicity to rotifers was observed. Analysis on a column of Sephadex LH-20 revealed that light-dependent haemolytic activity and inhibitory activity on cell-mediated light-independent haemolytic activity existed in two separate fractions (f-2 and f-3), suggesting that both activities might be derived from common compounds. Our results suggest that the photosensitising haemolytic toxin discharged from ruptured H. circularisquama cells has a relatively broad spectrum of phytoplankton toxicity, and that physical collapse of H. circularisquama cells can lead not only to the disappearance of its own toxicity, but also to mitigation of the effects of other HABs.
一种有害的甲藻——圆形异帽藻，对贝类和浮游动物褶皱臂尾轮虫具有高毒性。先前的一项研究发现，圆形异帽藻具有光依赖性和非光依赖性溶血剂，这可能是其毒性的原因。对圆形异帽藻溶血活性的详细分析表明，非光依赖性溶血活性主要通过完整细胞介导，而光依赖性溶血活性则由可从破裂细胞中释放的细胞内物质介导。由于无论光照条件如何，圆形异帽藻对轮虫都表现出相似的毒性，并且超声破碎的圆形异帽藻细胞对轮虫没有显著毒性，因此有人提出活细胞介导的非光依赖性溶血活性是观察到的对轮虫毒性的主要因素。有趣的是，圆形异帽藻的超声破碎细胞抑制了它们对轮虫的致死作用。对由破碎的圆形异帽藻细胞制备的细胞内容物（上清液）和细胞碎片（沉淀物）样本的分析表明，细胞内容物含有非光依赖性细胞介导溶血活性的抑制剂、影响圆形异帽藻细胞自身的毒素以及光依赖性溶血剂。从圆形异帽藻制备的乙醇提取物，据推测含有显示光敏溶血活性的卟啉衍生物，在对轮虫无显著毒性的浓度范围内，对海洋卡盾藻、古氏卡盾藻、米氏凯伦藻以及圆形异帽藻都表现出强毒性。在Sephadex LH - 20柱上的分析表明，光依赖性溶血活性和对细胞介导的非光依赖性溶血活性的抑制活性存在于两个不同的组分（f - 2和f - 3）中，这表明这两种活性可能来自共同的化合物。我们的结果表明，从破裂的圆形异帽藻细胞中释放的光敏溶血毒素具有相对广泛的浮游植物毒性谱，并且圆形异帽藻细胞的物理破裂不仅会导致其自身毒性消失，还会减轻其他有害藻华的影响。
