Ecological physiology of the black band disease cyanobacterium Phormidium corallyticum.
Abstract 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 30 degrees C. 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.