Ecological physiology of the black band disease cyanobacterium Phormidium corallyticum

Laboratory studies were carried out to assess the photosynthetic and nitrogen-fixing capabilities of the gliding, filamentous cyanobacterium Phormidium corallyticum. This species is found on coral reefs, and is one of the members of a pathogenic microbial consortium called black band disease of corals, a unique horizontally migrating microbial mat with an active sulfuretum. It was determined that P. corallyticum can perform oxygenic photosynthesis in the presence or absence of sulfide, but cannot conduct (DCMU-forced) anoxygenic photosynthesis with sulfide as electron donor. Photosynthesis vs. irradiance curves revealed a very low threshold for Pmax of < 30 muE m(-2) s(-1). Temperature optima for photosynthetic activity were at and above 30degreesC. Neither a laboratory culture of P. corallyticum nor freshly collected samples of the black band microbial consortium were capable of fixing N-2. Results are discussed in terms of the ecology of this coral disease. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.