<i>Bacillus</i> spp. Inhibit <i>Edwardsiella tarda</i> Quorum-Sensing and Fish Infection
2021
Rafaela A. Santos | Marta Monteiro | Fábio Rangel | Russell Jerusik | Maria J. Saavedra | António Paulo Carvalho | Aires Oliva-Teles | Cláudia R. Serra
The disruption of pathogen communication or quorum-sensing (QS) via quorum-quenching (QQ) molecules has been proposed as a promising strategy to fight bacterial infections. <i>Bacillus</i> spp. have recognizable biotechnology applications, namely as probiotic health-promoting agents or as a source of natural antimicrobial molecules, including QQ molecules. This study characterized the QQ potential of 200 <i>Bacillus</i> spp., isolated from the gut of different aquaculture fish species, to suppress fish pathogens QS. Approximately 12% of the tested <i>Bacillus</i> spp. fish isolates (FI). were able to interfere with synthetic QS molecules. Ten isolates were further selected as producers of extracellular QQ-molecules and their QQ capacity was evaluated against the QS of important aquaculture bacterial pathogens, namely <i>Aeromonas</i> spp., <i>Vibrio</i> spp., <i>Photobacterium damselae</i>, <i>Edwardsiela tarda</i>, and <i>Shigella sonnei</i>. The results revealed that <i>A. veronii</i> and <i>E. tarda</i> produce QS molecules that are detectable by the <i>Chr. violaceum</i> biosensor, and which were degraded when exposed to the extracellular extracts of three FI isolates. Moreover, the same isolates, identified as <i>B. subtilis</i>, <i>B. vezelensis</i>, and <i>B. pumilus</i>, significantly reduced the pathogenicity of <i>E. tarda</i> in zebrafish larvae, increasing its survival by 50%. Taken together, these results identified three <i>Bacillus</i> spp. capable of extracellularly quenching aquaculture pathogen communication, and thus become a promising source of bioactive molecules for use in the biocontrol of aquaculture bacterial diseases.
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