Phormidium corallyticum Ernest Glanneman
Image yourself in the Caribbean, out under the water and seeing all the beautiful coral surrounding you. All the vibrant colors, from greens, blues, reds, yellows, with all the life teaming from them. Now image that same place, except this time all the coral being pure skeletal white, with no life, and the only color remaining other than the white is a dark black band surrounding some of the coral. This is a site that is sadly becoming more of a reality because of a disease affecting the coral called Black Banding Disease. Black Banding Disease was first found in the corals of the Caribbean in the 1970’s on brain and star corals, and has since moved onto the other coral reefs of the world, with most recently cropping up in the Great Barrier Reef in Australia in 1995.
Coral Reefs are very sensitive to their environments, requiring a set range of temperature, solar radiation, and salinity to thrive. When one of those is disrupted, the coral reef can go into shock, making itself susceptible to disease, or in the worst cases, bleaching (the expulsion of all zooxanthella from the coral, killing it). One of those diseases is BBD, which starts as a small ring on the coral, then spreads outward in a radial pattern as a black band at about 4mm a day, killing the coral behind the band, leaving only the skeleton. BBD is passed from one coral to another through wave action, so once one coral is affected, it is easily passable to the surrounding coral.
BBD is not a single organism, but a colony of them, with the primary bacteria being Phormidium corrallyticum, a filamentous gliding Cyanobacteria. These cyanobacteria, along with the other organisms found, starve the coral of oxygen as well as expose the coral to hydrogen sulfide near the band, killing the coral. The coral’s only defense against the disease is the creation of excess mucus, which smothers the bacteria. BBD does not affect all Coral naturally, with certain coral being immune to it effects unless under eutrophic conditions, which allows the bacteria to move onto an immune coral.
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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