Identification of microbes associated with coralline lethal algal disease and its relationship to glacial ice melt (global warming)

A cluster of five bacterial species consistently associated with Corraline Lethal Orange Disease (CLOD) have been identified. Crostose Red Alga Porolithon spp. have been affected by this disease, and exhibited high mortality, according to studies performed from 1996 through 2001. The decayed crostose algae were surrounded by a rapidly expanding orange-yellow pigmented biofilm attacking the Porolithon crusts with expanding circles of orange rimmed (about 1.0 cm wide) dead skeleton. The 16S rRNA genes from these bacteria were sequenced and found to correspond with five different species of glacial ice bacterium genetically related to the genus Planococcaceae with a degree of relatedness of 98-99% to type strains Planococcus citreus, Planococcus sp. (SOS Orange) and P. mcmeekinii, these bacteria all fall within a group of Antarctic ice bacterium. Also found was, Bacillii with a degree of relatedness of 99% to type strain Bacillus pumilus, and Pseudomonas with a close similarity of 99% to type strain Pseudomonas oleovorans. These three different bacteria were found to be culturable from all diseased specimens and in vitro introduction of these isolates onto healthy algae initiated lesions identical to CLOD. Temperature experiments indicate that higher temperatures are a critical factor in infection and the rate of spread. When temperatures are lowered below 23 degree C during aquaria experiments the orange lesion degrades. Warmer temperatures may be linked to the virulence and rate of spread of these pathogens. Glacial ice-cap melting due to global warming may be circulating increased concentrations of cold adapted bacteria to lower latitudes in the tropics causing diseases that are affecting encrusting substrates that provide foundational habitat for corals and other marine organisms.