CATALASE-INDUCED AND SUPEROXIDE DISMUTASE-INDUCED MORPHOLOGICAL-CHANGES AND GROWTH-INHIBITION IN THE RED TIDE PHYTOPLANKTON CHATTONELLA-MARINA

Chattonella is one of the most toxic red tide phytoplankton and causes severe damage to fish farming, Recent studies demonstrated that Chatt onella sp, generates superoxide and hydroxyl radicals, which may be re sponsible for the toxicity of this plankton. However, little is known about the mechanism of the production of oxygen radicals by Chattonell a, and the role of oxygen radicals in Chattonella themselves is also u nclear, In this study, we found that superoxide dismutase (SOD) and ca talase inhibited the growth of Chattonella marina concomitant with the ir morphological changes, In the presence of these enzymes, the shape of vegetative C. marina cells changed from spindle to round, Furthermo re, the generation of oxygen radicals by C. marina depended on the gro wth phase; the rate of superoxide and hydrogen peroxide generation was the highest during exponentially growing phase and subsequently decre ased to one-fifth of the maximal level in the stationary growth phase, These results suggest that oxygen radicals generated by C. marina pla y an essential role in their own survival, especially in cell division .