The Production Of Hemolytic Toxins And Haemolytic Properties In Karenia Mikimotoi Hasen

Karenia mikimotoi Hasen is one of the HABs-causing organisms in temperate and subtropical zones of the world. Some hemolytic substances produced by K. mikimotoi were considered to result in the serve mortality of fishes and invertebrates, and harm to the cultivation and ecological system.In this study, the biochemical characters and the effect of biological factors on haemolytic toxins production were studied. First, the components of the hemolytic toxin from K. mikimotoi in laboratory were analyzed by thin-layer chromatography (TLC), and molecular structures were analyzed. Second, effects of temperature, pH, different divalent cations and lipids on the hemolysis induced by Karenia mikimotoi Hasen were observed, and the hemolytic properties were analyzed. Third, in order to obviate the contact-inhibition in alga-alga competion, a glass bottle containing a glass tube cage with a sealed nylon-mesh bottom was used to explore the effects of co-occuring algae and grazer on haemolytic toxins production in K. mikimotoi.The results showed that the hemolytic activity of K. mikimotoi was 64.69±6.43 HU·L^-1 and 6.17±0.61×10^-6 HU·cell^-1. There were at least 3 components in the hemolytic toxin from K. mikimotoi cultures in laboratory, and their R_f value was 0.64 (â… ), 0.57 (â…¡), 0.086 (â…¢) respectively. The hemolytic activity increased with the temperature during 0℃-37℃. pH had a distinguished effect on the haemolytic activity, and the highest activity was at pH 6.0. When the concentration was 5 mmol·L^-1, the divalent cations such as Cu²⁺, Mg²⁺, Mn²⁺, Ca²⁺, Co²⁺, Zn²⁺ and Hg²⁺ had different inhibition on the hemolysis, in which Hg²⁺ was the strongest inhibitor. High concentration of Hg ²⁺ induced a rapid and cooperative cell aggregation, and then prevent penetration of Hg²⁺ into the cells, which did not only avoid any haemolysis induced by the Hg²⁺ entrance, but also inhibited the destruction by the hemolytic toxin. However, this phenomenon could be eliminated by EDTA. Different from the L-α-Phosphatidic acid, Cholesterol, Lecithin and Sphingomyelin, Gangliosides have a significant inhibition on the hemolysis induced by K. mikimotoi, suggesting that the gangliosides might be the specific receptor of haemolytic toxins on the erythrocyte membrane. Prorocentrum donghaiense and Alexandrium tamarense were shown to have an inhibition on the growth of K. mikimotoi, but to promote the heamolytic toxins production when co-cultured with K. mikimotoi. The ingestion of Moina mongolica was also showed to induce the production of haemolytic toxins in K. mikimotoi. These results provide information for appreciation and evaluation to the hazard of red tide caused by K. mikimotoi.