ANTIMICROBIAL ACTIVITY OF A RED-SEA SOFT CORAL, PARERYTHROPODIUM-FULVUM FULVUM - REPRODUCTIVE AND DEVELOPMENTAL CONSIDERATIONS

Living corals are frequently colonized by bacteria that may be pathoge nic. One way they are able to combat microbial attack is by chemical d efense. This is especially critical for the early developmental stages of the coral. Extracts from various reproductive and developmental st ages of the Red Sea soft coral Parerythropodium fulvum fulvum exhibite d antimicrobial activity against several cooccurring and potentially p athogenic marine bacteria. High activity was found particularly agains t Vibrio sp. (strain P-l), isolated from a necrotic coral tissue. Howe ver, no antimicrobial activity was observed against the coral-associat ed bacterial strains isolated from the coral tissue and its mucoid sur face. The minimum inhibitory concentration of the coral crude extract against this Vibrio sp, was 1.25 mg ml(-1). Bioassay-guided fractionat ion of the coral extract indicated that the antimicrobial activity was due to the presence of a range of secondary compounds of different po larities, which were also present in the tissue in trace amounts. The antimicrobial activity was present in all reproductive and development al stages of the coral against the sensitive bacteria. This study prov ides the first comprehensive evidence for antimicrobial activity in co ral larvae against co-occurring marine bacteria. It is concluded that antimicrobial activity detected in the extracts of P. f. fulvum is spe cific rather than broad spectrum. This specificity may be important in order to enable certain bacteria to Live in close association with th eir coral host.