28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Black Band Disease of Corals: A Pathogenic Microbial Consortium Laurie L. Richardson1, T. Shay Viehman2, and DeEtta Mills1 1Department of Biological Sciences, Florida International University, Miami, Florida  33199;  2Biscayne Bay Park, 9700 SW 328th St., Homestead, FL 33033 Black band disease (BBD) is the first coral disease reported in the literature (1973). It has been studied for 30 years, but we still do not know its etiology, definitively.  When viewed under the microscope a diverse microbial community is always present and duly noted by most investigators.  In the 1970s three different pathogens were proposed: a cyanobacterium (Oscillatoria submembranaceae); a sulfide-oxidizing bacterium (Beggiatoa spp.); and a sulfate-reducing bacterium (Desulfovibrio spp.).  All were based solely on microscopic observations, with no attempts made at isolation.  In the 1980s another group concluded that the primary pathogen was, in fact, the cyanobacterium, which they renamed, Phormidium corallyticum.  The characterization was based on morphology.  Inoculation experiments utilized clumps of fresh BBD material, but Koch’s Postulates were not satisfied.  In the 1990s our group proposed that BBD is a pathogenic microbial consortium, without a primary pathogen.  We demonstrated that the BBD community was functionally dominated by populations of sulfate-reducing, sulfide-oxidizing, and phototrophic cyanobacteria that produce dynamic chemical microenvironments and expose the coral to lethal conditions of anoxia and sulfide. We too could not purify the cyanobacterium, which we obtained in culture and identified based on morphology.  Most recently, in 2002, two groups used non-cultivative molecular techniques (PCR and 16S rDNA analyses) to assess the microbial community of BBD. One found >50 BBD and the other >500 distinctive bacteria (as opposed to those in water column and on healthy and dead corals).  Neither group found a sequence that matched either the cyanobacterial genus Phormidium, or Beggiatoa.  One group included our cultured “P. corallyticum” in their research, which they found to be most closely related to an entirely different cyanobacterial genus – Geitlerinema (97% sequence homology). Both groups consistently found a heterotrophic bacterium, Cytophaga sp., known to be a fish pathogen, and one group consistently detected a common sequence to the pathogen of juvenile oyster disease.  Both groups have proposed these as potential BBD primary pathogens.  This talk will cover the above story and will include some of our own recent results using molecular techniques to study this fascinating coral disease. Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page