Bacterial populations and adaptations in the mucus layers on living corals1

Abstract

The external mucus layers of the stony coral Porites astreoides and the soft corals Palythoa sp. and Heteroxenia fuscesens are inhabited by communities of marine heterotrophic bacteria. Population levels of bacteria in coral mucus may be regulated by the self‐cleaning behavior of the host. Bacterial populations in coral mucus respond to stresses applied to the host coral by growing to higher population levels in the mucus, indicating that these are populations of viable organisms closely attuned to host metabolism. Members of these microbial populations utilize the mucus compounds and may play a role in processing coral mucus for reef detritus feeders. One such species, Vibrio alginolyticus, grows rapidly on Heteroxenia mucus, is attracted to dissolved mucus, and possesses a mechanism to maintain itself on the coral surface.