Quorum sensing (QS), acts as one of the gene regulatory systems that allow bacteria to regulate their physiological activities by sensing the population density with synchronization of the signaling molecules that they produce. Here, we report a marine isolate, namely strain T47, and its unique AHL profile. Strain T47 was identified using 16S rRNA sequence analysis confirming that it is a member of Vibrio closely clustered to Vibrio sinaloensis. The isolated V. sinaloensis strain T47 was confirmed to produce N-butanoyl-L-homoserine lactone (C4-HSL) by using high resolution liquid chromatography tandem mass spectrometry. V. sinaloensis strain T47 also formed biofilms and its biofilm formation could be affected by anti-QS compound (cathechin) suggesting this is a QS-regulated trait in V. sinaloensis strain T47. To our knowledge, this is the first documentation of AHL and biofilm production in V. sinaloensis strain T47.
The link between quorum sensing in Vibrio campbellii and its virulence towards tiger grouper (Epinephelus fuscoguttatus) was investigated using V. campbellii wild type and quorum-sensing mutants with inactive quorum sensing or constitutively maximal quorum-sensing activity, and signal molecule synthase mutants. The results showed that wild-type V. campbellii is pathogenic to grouper larvae, causing more than 50% mortality after 4 days of challenge. Furthermore, the mortality of larvae challenged with the mutant with maximally active quorum sensing was significantly higher than that of larvae challenged with the wild type, whereas a higher survival was observed in the larvae challenged to the mutant with a completely inactive quorum-sensing system. Grouper larvae challenged with either the signal molecule synthase triple mutant, the harveyi autoinducer-1 (HAI-1) synthase mutant and the autoinducer-2 (AI-2) synthase mutant showed higher survival than larvae challenged with the wild type. In contrast, larvae challenged with the cholerae autoinducer-1 (CAI-1) synthase mutant showed high mortality. This indicates that HAI-1 and AI-2, but not CAI-1, are required for full virulence of V. campbellii towards grouper larvae. Our data suggest that quorum-sensing inhibition could be an effective strategy to control V. campbellii infections in tiger grouper.