Polyamines control the growth of the fish-killing dinoflagellate Karenia mikimotoi in culture

Effects of intracellular polyamines on the growth of the harmful dinoflagellate Karenia mikimotoi were investigated in culture experiments using an axenic culture. Polyamines were analyzed with HPLC. Free norspermine was the most abundant polyamine during growth of K. mikimotoi. Cellular norspermidine contents increased significantly during the exponential growth phase with increasing growth rate. The maximum growth yield of K. mikimotoi was reduced by the polyamine biosynthetic inhibitor, d,l-alpha-difluoromethylornithine (DFMO) which inhibits ornithine decarboxylase. These results suggest that polyamines, especially free norspermine, play significant roles in the growth of K. mikimotoi.