Abstract Summary
Currently, there is a widespread coral disease outbreak occurring on the reefs of Florida that has resulted in significant mortalities of 11 of the 24 species surveyed. This unprecedented outbreak provides a unique but time-sensitive opportunity to address critical questions about coral disease. This project examined potential etiological agents as well as putative probiotic microorganisms that could be used to treat or prevent infections. Transmission occurred during manipulative aquarium studies between diseased Montastraea cavernosa from the Fort Lauderdale area or Colpophyllia natans from the Keys and healthy fragments. Therefore, diseased fragments were treated with antibiotics to determine if a bacterial pathogen is involved. Disease progression was halted in 12 out of 13 diseased M. cavernosa fragments with a combinational amoxicillin/kanamycin treatment. Colpophyllia natans was less tolerant of combinational treatments while disease progression was comparatively faster with this species, however, treatment with nalidixic acid was able to slow or arrest disease progression in five out of eight fragments. Accordingly, bacteria were important for disease progression, so isolates from diseased M. cavernosa, C. natans, and Meandrina meandrites were tested for virulence during laboratory infection experiments. Various Vibrionaceae, Alteromonadales, and Rhodobacteraceae isolates are suspected to be pathogenic and are currently being investigated. In parallel to this work, bacterial isolates were cultured from fragments seemingly resistant to disease and then screened for antibacterial activity to isolate potential protective bacteria (probiotics). When one of these isolates, Pseudoalteromonas tunicata strain McH1#7, was inoculated onto diseased C. natans, disease progression was significantly slowed in three of six fragments. Subsequent NMR analysis of McH1#7 extracts identified the antibiotic korormicin while genome sequencing predicts the production of the antibacterials marinocine and tetrabromopyrrole. Further experiments are planned, which could potentially determine the etiological agent(s) responsible for this disease outbreak and potential biological controls for disease.
