Production of Superoxide Anion and Hydrogen Peroxide by the Red Tide Dinoflagellate Karenia mikimotoi

Abstract

We found that the red tide dinoflagellate Karenia mikimotoi ( Gymnodinium mikimotoi ) generates reactive oxygen species (ROS). In chemiluminescence analysis using an O 2 − specific probe, a slightly lower but significant level of O 2 − was detected in a K. mikimotoi cell suspension as compared to one containing Chattonella marina , a well-known ROS-producing red tide phytoplankton. Interestingly, the chemiluminescence response pattern caused by K. mikimotoi was different from that of C. marina , although both responses were almost completely abolished in the presence of superoxide dismutase (SOD). By fluorescence spectrophotometric analysis, H 2 O 2 was also detected in the K. mikimotoi cell suspension, but the level of H 2 O 2 was approximately 10% of that in the C. marina suspension based on the cell number. No significant increase in O 2 − generation by K. mikimotoi was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus substances prepared from the skin and gills of yellowtail, whereas C. marina generated an increased level of O 2 − in response to these stimuli. Furthermore, O 2 − production in C. marina , but not in K. mikimotoi , was inhibited by treatment with proteinase K.