Metabolic complexities and heterogeneity in quorum sensing signaling molecules in bacteria isolated from black band disease in a Caribbean coral.

Coral diseases contribute to the worldwide loss of coral reefs, with the Black Band Disease (BBD) being a prominent example. BBD is an infectious condition with lesions with a pigmented mat composed of cyanobacteria, sulphate-reducing, sulphide-oxidizing, and heterotrophic bacteria. We compared the heterotrophic bacterial communities of healthy and BBD-affected colonies of the Caribbean coral Orbicella faveolata using culture-dependent and -independent techniques. Twenty and 23 bacterial isolates were identified from healthy and diseased tissues, respectively, which differed in their capacities to metabolize carbohydrates and citrate, either anaerobically or aerobically. They also differed in their quorum-sensing (QS) activity, as QS signaling molecules were found exclusively, and QS-inhibition was found primarily, in isolates from diseased tissues. Screening of bacterial diversity by 16SrDNA metabarcoding showed that members of the bacterial genera Muricauda and Maritimimonas were dominant in healthy tissues whereas members of the cyanobacterial genus Roseofilum were dominant in diseased tissues. These results suggest that bacterial dysbiosis can be linked with altered bacterial communication, likely leading to diachrony and imbalance that may participate in the progression of BBD. Investigating physiological traits and QS-based communication offers insights into the onset and progression of coral infections, paving the way for novel strategies to mitigate their impact.