Flower Garden Banks National Marine Sanctuary: Antimicrobial Properties of Bacteria Associated with the Boulder Star Coral, Montastrea faveolata

Overview Corals have been shown to harbor unique microbial communities associated with their surface mucopolysaccharide layer, which is hypothesized to play an important role in defense against invading pathogens (Ritchie and Smith, 2004). In this study, bacterial associates of Montastraea faveolata surface mucus were compared between the healthy, disease-free reefs of the Flower Garden Banks National Marine Sanctuary and the disease-prone reefs of the Florida Keys National Marine Sanctuary. Bacteria isolated from the surface mucus of healthy M. faveolata colonies from both locations were subcultured to purification and screened for antibacterial activity against a range of human pathogens. Twelve bacterial isolates from the Flower Gardens West Bank displayed varying degrees of antibacterial activity against Bacillus subtilis. Genetic identification of antibiotic-producing bacteria places five of these isolates within the genus Vibrio. A Pseudoalteromonas sp. isolated from a M. faveolata colony located in the Flower Gardens East Bank displayed antibacterial activity against all strains tested, providing a potentially novel source for the identification of broad-spectrum antibiotics. No antibacterial activity was detected from bacterial associates of M. faveolata colonies in the Florida Keys, suggesting that M. faveolata may harbor a higher percentage of beneficial bacterial associates in healthy reef systems. Eleven of the twelve isolates from the Flower Gardens West Bank displaying antibacterial activity were isolated from subcultures grown on mucus-treated growth media. This result implicates a bacterial contribution to antibiotic production in coral mucus and suggests a novel symbiotic mechanism between corals and bacteria.