IDENTIFICATION OF Vibrio SPECIES FROM RECIRCULATING AQUACULTURE SYSTEMS AND INTERACTIONS WITH Bacillus spp.

Losses during the production of marine fish larvae remain a bottleneck to the expansion of the marine aquaculture industry. In particular, the presence of Vibrio, a genus of bacteria associated with opportunistic disease in marine finfish and shellfish, is negatively correlated with larval fish survival in aquaculture systems. Previous studies in our lab indicate a Bacillus spp. probiotic significantly improves larval survival; however, the mechanism behind these benefits is unknown. The goal of this study was to characterize the interactions between the probiotic strains and Vibrio species present in marine recirculating aquaculture systems. In this study, Vibrio were isolated from a variety of fish species and life stages at the Mote Aquaculture Research Park (MAP) using thiosulfate citrate bile salts sucrose (TCBS) agar. Isolates were classified by sequencing the rpoB gene. Vibrio sequences were compared to the NCBI database via BLAST and reference strains that contained the highest percent sequence similarity were included in a phylogenetic tree of all found sequences. A total of 128 isolates were collected from MAP, of which 26 have been sequenced to date. Twelve species of Vibrio were identified, with the greatest diversity (six species) present in larval Almaco Jack. Four species were found in juvenile Common Snook, and three were found in adult Redfish. Antagonism studies were performed between two probiotic Bacillus strains and a subset of Vibrio strains. Bacillus inhibited growth of 6 Vibrio species, including 4 potential fish pathogens (V. harveyi, V. parahaemolyticus, V. rotiferianus, and V. alginolyticus). Continuing investigation of Vibrio communities in these systems will identify opportunists of potential concern for larval rearing and help to elucidate beneficial mechanisms behind the Bacillus probiotic, allowing for more targeted treatment methods to increase larval survival and promote growth of the aquaculture industry.