Inhibitory effect of halocyamine, an antimicrobial substance from ascidian hemocytes, on the growth of fish viruses and marine bacteria.

Halocyamine A, an antimicrobial substance isolated from hemocytes of the solitary ascidian Halocynthia roretzi, inhibited in vitro the growth of fish RNA viruses (infectious hematopoietic necrosis virus and infectious pancreatic necrosis virus). Pretreatment of RNA virus with halocyamine A reduced the infectivity of the virus toward host cells. The growth of marine bacteria, Achromobacter aquamarinus and Pseudomonas perfectomarinus, was also inhibited by halocyamine A but that of Alteromonas putrefaciens and Vibrio anguillarum was not. These results suggest that halocyamine may have a role in the defense mechanisms of H. roretzi against marine viruses and bacteria.