Elevated temperature enhances short-to medium-chain acyl homoserine lactone production by black band disease-associated vibrios

Black band disease (BBD) of corals is a horizontally migrating, pathogenic, polymicrobial mat community which is active above a temperature threshold of 27.5. degrees C on the reef. Bacterial isolates from BBD, the surface mucopolysaccharide layer (SML) of healthy corals and SML of healthy areas of BBD-infected corals were tested for production of short-to medium-chain acyl homoserine lactones (AHLs) using the Chromobacterium violaceum CV026 reporter strain. Of 110 bacterial isolates tested, 19 produced AHLs and 15 of these were from BBD. Eight AHLs were identified using LC-MS/MS, with 3OHC4 the most commonly produced, followed by C6. AHL-producing isolates exposed to three temperatures (24 degrees C, 27 degrees C, 30 degrees C) revealed that production of three AHLs (3OHC4, 3OHC5 and 3OHC6) significantly increased at 30 degrees C when compared to 24 degrees C. 16S rRNA gene sequencing revealed that all of the AHL-producing BBD isolates were vibrios. Metagenomic data of BBD communities showed the presence of AHL (and autoinducer-2) genes, many of which are known to be associated with vibrios. These findings suggest that quorum sensing may be involved in BBD pathobiology and community structure due to enhanced production of quorum-sensing signal molecules (AHLs) above the temperature threshold of this globally distributed coral disease.