Vibrio shiloi is the causative agent of bleaching of the coral Oculina patagonica in the eastern Mediterranean Sea. Infection and subsequent bleaching occur only when water temperatures approach their maximum of 29-30°C. Virulence mechanisms of V. shiloi include: (i) chemotaxis to the mucus of O. patagonica, (ii) adhesion to a β- galactoside-containing receptor on the coral surface, (iii) penetration into coral epidermal cells, (iv) differentiation into a viable-but-not-culturable (VBNC) state, (v) intracellular multiplication, and (vi) production of toxins that inhibit photosynthesis, and bleach and lyse zooxanthellae. The toxin that inhibits photo-synthesis is a proline-rich, 12 amino acid peptide. The adhesion, multiplication and toxin production steps occur only at high temperature, providing a biochemical explanation for the effect of temperature on the bleaching of O. patagonica. The generality of the bacterial bleaching hypothesis is discussed in terms of existing indirect evidence and how the hypothesis can be tested using information from the V. shiloi/O. patagonica model system.
|Title of host publication
|Proceedings of the Ninth International Coral Reef Symposium
|Published - 2002