Bacillus spp. Inhibit Edwardsiella tarda Quorum-Sensing and Fish Infection

Abstract

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. Bacillus 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 Bacillus spp., isolated from the gut of different aquaculture fish species, to suppress fish pathogens QS. Approximately 12% of the tested Bacillus 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 Aeromonas spp., Vibrio spp., Photobacterium damselae, Edwardsiela tarda, and Shigella sonnei. The results revealed that A. veronii and E. tarda produce QS molecules that are detectable by the Chr. violaceum biosensor, and which were degraded when exposed to the extracellular extracts of three FI isolates. Moreover, the same isolates, identified as B. subtilis, B. vezelensis, and B. pumilus, significantly reduced the pathogenicity of E. tarda in zebrafish larvae, increasing its survival by 50%. Taken together, these results identified three Bacillus 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.

Oral vaccination of fish against vibriosis using spore-display technology

“…The mortality of orally vaccinated European seabass was reduced from 40% to 13%. The previously reported adjuvant properties of B. subtilis spores ( 45 , 72 , 73 , 99 ) together with the immunomodulatory capacity of their metabolites ( 40 , 102 ) might have contributed to the protection observed ( 14 ).…”

“…To evaluate the protective effect of OmpK-carrying spores, 4 dpf larvae were distributed into 6-well plates containing 10 larvae per well in 5 mL of Egg water to acclimatize to the experimental conditions. At 6 dpf, larvae were treated for 2 h, [following previously established protocols (40)], with spores suspensions containing 1x10 8 CFU mL -1 of each recombinant strain (CRS220, CotY-H6-OmpK and CRS221, H6-OmpK-CotY), or the parental WT B. subtilis 168 strain. At 9 dpf, larvae were challenged by immersion during 12h with 3×10 8 CFUs mL -1 of V. anguillarum or 1×10 8 CFUs mL -1 of V. parahaemolyticus (following established models of infection previously developed by us, unpublished data).…”

In vitro selection of autochthonous bacterium with probiotic potential for the neotropical fish piauçu Megaleporinus microcephalus

“…It is a facultative and mobile Gram-negative bacterium, causing Edwardsiellosis disease, which can generate great economic losses in aquaculture (Lima et al, 2008;Woo and Bruno, 2010). A study carried out with isolates of Bacillus subtilis, Bacillus velezensis and Bacillus pumilus, significantly reduced the pathogenicity of E. tarda in zebrafish larvae increasing survival by 50%, and those infections may have occurred via the skin, gills and intestine, thus he observed promoting health through the use of probiotics (Santos et al, 2021). K. pneumoniae and E. tarda, however the pathogenesis of bacteria of the genus Salmonella sp.…”

Quorum Quenching Strains Isolated from the Microbiota of Sea Anemones and Holothurians Attenuate Vibriocorallilyticus Virulence Factors and Reduce Mortality in Artemiasalina

“…The use of QQ bacteria as biocontrol in aquaculture has also been proposed to other species, such as Bacillus spp. [ 89 , 90 ] that were able to increase the survival rate of fish and crustacean models. Nevertheless, up to our knowledge, this is the first report of A. junii , M. echini , R. aquimaris , and P. sihuiensis as biocontrol strains in aquaculture.…”