Is there a case for the “bacterial bleaching hypothesis’? Oculina patagonica / Vibrio shiloi revisited

3 thoughts on “Is there a case for the “bacterial bleaching hypothesis’? Oculina patagonica / Vibrio shiloi revisited”

  1. Bacterial diseases are notoriously difficulty to prove or disprove eg. stomach ulcers are a common human complaint which only quite recently were found to be caused by a bacterial pathogen. The methods you have used would not detect this disease agent for example? Sorry haven’t read the original literature lately but has anyone done any pathogenicity experiments and used Koch’s postulates to isolate and test for a bacterial agent? These make a pretty airtight test and Vibrios are common pathogens which have been well studied so this would be quite simple for a marine microbiologist to do.


  2. We conducted positive controls to ensure that the propsed cultured pathogen
    (previously used to illict a bleaching response in aquarium maintained corals)
    could be detected using FISH and bacterial probes. This was sucessful and we
    were able to detect the bacterial population associated with the coral tissues
    from samples that had been exposed to Vibrio shiloi in experimental scenarios.
    However we were not able to find this same pattern in bleached corals from the
    feild. This raises some interesting questions on determining what is a
    pathogen of corals and bacterial populations that are able to colonise corals in
    artifical situations. Unfortunately in working with corals we rely on very few
    signs to determine disease. These signs include :
    * bleaching (loss or symbionts or their associated pigments, leaving the coral
    host tisues white
    * tissue loss. which leave a white exposed skeleton
    * colour patterns eg: yellow lines, white spots ect

    So the questions arise are the few signs that we can see macroscoically enough
    to show that a disease we may replicate in aquaira is the same disease or
    disease progression we see in the field? This is particalurly evident when we
    consider bleaching (as we see it) is a generalised stress response.


  3. Hi Tracy- When you say pattern, do you mean pattern as seen in thermally stressed corals during heat-stroke, meaning the response being expulsion?

    I am very concerned as to how coral diseases are interpreted. This bacterial bleaching hypothesis should be called bacterial paling or simply a bacterial disease, as there is no proof that coral diseases are caused on a mass scale as seen in thermal hot-spot bleaching that leads to the loss or ejection of zoox from the host endoderm. Most of these diseases are either tissue diseases or zoox targeted infections that are caused by localized micro-flora. I have a paper in review that compares YB Pacific from YB Caribbean with the 5 novel Vibs we isolated from Caribbean YB infections. We see similar and sometimes identical flora, however, there are a different consortium groups associated with the muco-layers of YB infected corals found in the Carib and Pacific. We need to clarify these physical differences as well as explain to the masses that diseases and coral reef bleaching are different mechanistically…. explaining that these coral killers are different in how that affect and attack the coral is important.

    Why do I say this? Because policy makers are getting miscommunications from the press, such as : These scientists are confused, first they say coral bleaching is thermally induced as a result of global warming….and not we find out that its really an infection…. This give policy makers another reason to drag their feet because it shows we disagree. This is why I am glad that I had training as a cell biologist first investigating corals and zoox…. Then when I conducted my PhD with a marine microbiologist I finally understood why “we cell zoox biologists” differ in our thinking than microbiologists. We coral biologists start with the zoox responses and the microbiologists begin with the microbe responses…


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