ANTIMICROBIAL ACTIVITY OF EXTRACTS OF CARIBBEAN GORGONIAN CORALS

Extracts of 39 species of Caribbean gorgonians were tested for antimic robial activity against 15 strains of marine bacteria. The bacteria co nsisted of three opportunistic pathogens, Vibrio parahaemolyticus, Leu cothrix mucor, and Aerococcus viridans, and 12 strains isolated from e ither healthy or decayed gorgonians. Overall, only 15% (79 out of 544) of the tests resulted in antibacterial activity with 33% (13 out of 3 9) of the gorgonians inhibiting only one bacterial strain and 23% (9 o ut of 39) showing no activity. The extracts of four Pseudopterogorgia species showed relatively high levels of activity, inhibiting 43 to 86 % of the bacterial strains. The potency of the active Pseudopterogorgi a species was variable, however, and three additional Pseudopterogorgi a species were inactive against all bacterial strains. With the except ion of one sensitive strain, Vibrio species were resistant to gorgonia n metabolites. Our results indicate that organic extracts of most Cari bbean gorgonians do not possess potent, broad-spectrum antibacterial a ctivity inhibitory to the growth of opportunistic marine pathogens and bacteria associated with healthy and decayed gorgonian surfaces. Thes e findings suggest that the inhibition of bacterial growth is not the primary ecological function of gorgonian secondary metabolites and tha t bacteria may not be important selective agents in the evolution of g orgonian secondary chemistry.