Development of alternative in situ treatments for stony coral tissue loss disease

Specific tasks for this project were (1) Screening for novel probiotic strains and laboratory testing, (2) development of an improved 96-well plate-based assays for higher-throughput screening, (3) to further explore the connection between Vibrio coralliilyticus and more virulent SCTLD lesions, (4) optimal storage conditions for coral samples to screen for VcpA, and (5) Search for the pathogen(s) responsible for SCTLD using more narrow-spectrum antibiotics with RNA-based sequencing to identify potential pathogens.

During the project, we have developed a higher-throughput pipeline for screening potential probiotics as well as deriving a greater amount of information to make more informed decisions on what probiotics to move forward for coral experiments. For our VcpA RapidTests, we have determined the appropriate storage and shipping conditions for coral samples to be screened for VcpA. Corals with progressive sub-acute tissue loss appear to develop acute tissue loss after exposure to cultures of V. coralliilyticus. Lesions that just have bleaching or non-progressive tissue loss do not appear to be altered after exposure to V. coralliilyticus, suggesting that this opportunistic pathogen may require active external tissue damage from SCTLD to initiate a coinfection. Lastly, from our antibiotic treatment experiments, it appears that SCTLD could be arrested with colistin, but not vancomycin.