Antibiofilm Activity of the Marine Probiotic Bacillus subtilis C3 Against the Aquaculture-Relevant Pathogen Vibrio harveyi

V. harveyi is a well-known pathogen-inducing vibriosis, especially for shrimp, fish, and invertebrates. Its virulence is related to biofilm formation and this negatively impacts the aquaculture industry. Therapeutic strategies such as the utilization of probiotic bacteria may slow down Vibrio infections. In this study, we investigated the potential antibiofilm activity of the probiotic Bacillus subtilis C3 for aquaculture. First, B. subtilis C3 biofilm was characterized by confocal laser scanning microscopy (CLSM) before testing its bioactivities. We demonstrated antibiofilm activity of B. subtilis C3 culture supernatant, which is mainly composed-among other molecules-of lipopeptidic surfactants belonging to the surfactin family as identified by ultra-high-performance liquid chromatography (UHPLC)-MS/MS. Their antibiofilm activity was confirmed on V. harveyi ORM4 (pFD086) biofilm by CLSM. These findings suggest that the marine probiotic B. subtilis C3 might inhibit or reduce Vibrio colonization and thus decrease the associated animal mortalities.