Human gut bacteria causing disease in Caribbean coral

US researchers have revealed for the first time that a bacterial species associated with the human gut can cause disease in marine invertebrates, following the discovery that such a bacteria is responsible for white pox disease in Caribbean coral.

The research, which is published in the Proceedings of the National Academies of Science (PNAS), involved studies of populations of the shallow-water Caribbean elkhorn coral, Acropora palmata, which are being decimated by white pox disease, with losses of around 70% in the Florida Keys. The disease is characterised by white lesions where the tissue has disappeared from the skeleton, and which grow at an average rate of 2.5 square centimetres per day, but in some cases as fast as 10.5 square centimetres per day.

The culprit is a common faecal enterobacterium, Serratia marcescens, which is present in humans, as well as in other animal species and as a free-living microbe in water and soil. It has already been linked to disease in both marine and freshwater fish, including white perch in the sewage-polluted Black River. “Sewage may serve either as the source of S. marcescens or as a stressor of fish, increasing susceptibility to disease,” say the researchers.

The researchers note that as the disease spreads most rapidly at warmer times of year due to the stress that higher temperatures cause to corals, predictions of ocean temperature rises due to global warming do not bode well for the elkhorn.

Due to the findings of the study, the researchers have proposed renaming white pox disease acroporid serratiosis. Research is continuing into whether white pox in regions other than the Caribbean can be attributed to S. marcescens, and whether the pathogen affects other coral species on which the disease could take a different form.

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