Vibrios in Coral Health and Disease

The hypothesis accepted by most coral biologists who study coral bleaching is mass bleaching, which is the result of photobleaching of the endosymbiotic zooxanthellae. Basically, this hypothesis states that the photosynthetic apparatus of the algae is constantly undergoing photodamage in the light. Koch's postulates were applied to demonstrate that Vibrio shiloi is the causative agent of the bleaching disease of Oculina patagonica. The β-galactoside-containing receptor that V. shiloi recognizes on the O. patagonica surface is present in the coral mucus. The bacteria adhere to a β-galactoside-containing receptor on the coral surface. This was demonstrated by binding the coral mucus to enzyme-linked immunosorbent assay plates: the bacteria adhered avidly to the mucus-coated plates. Electron micrographs of thin sections of O. patagonica following infection with V. shiloi demonstrated large numbers of bacteria in the epidermal layer of the coral. Moreover, using monoclonal antibodies specific to V. shiloi, it was shown that the observed intracellular bacteria were, in fact, V. shiloi. V. coralliilyticus is an etiological agent of bleaching of the coral Pocillopora damicornis on coral reefs in the Indian Ocean and Red Sea. Based on phenotypic and genotypic characteristics, V. coralliilyticus was classified as a new species. Yellow blotch (also called yellow band) disease of the major reef-building coral of the Caribbean Sea, Monastraea spp., is well documented. Coral tumors are not transmitted between colonies, even after fusion of healthy and tumor coral fragments. Studies have indicated that healthy parts of a coral that contains a tumor eventually deteriorate.