Quorum Quenching Bacteria Bacillus velezensis DH82 on Biological Control of Vibrio parahaemolyticus for Sustainable Aquaculture of Litopenaeus vannamei

Abstract

Aquatic pathogens such as Vibrio parahaemolyticus cause a bacterial infection that reduces the economic benefits of aquaculture and affects the food quality and safety of human beings. Quorum quenching (QQ) is considered a novel strategy of microbial antagonism that inhibits pathogens and reduces the abuse of antibiotics. This study investigates a QQ bacterial strain, Bacillus velezensis DH82 from the deep sea Yap trench, in vitro to examine the effects of DH82 and its functional products against V. parahaemolyticus, focusing on the Quorum sensing (QS) regulation and the inhibition of pathogenicity and bacterial growth. The study also conducted in vivo investigation in the aquaculture of Litopenaeus vannamei challenged with V. parahaemolyticus by immersion and injection challenge. The results of the QS regulator transcription level demonstrated the multiple QQ enzymes in DH82 regulated the pathogenicity but could not fully control the biofilm formation; the effective antibacterial activity of extracellular peptides on microbial antagonism verified the inhibition on bacterial growth of V. parahaemolyticus. The in vivo experiment in aquaria demonstrated the effective enrichment of DH82 and inhibition of Vibrio in both the aquatic system and the shrimp intestine. The dietary DH82 relieved the negative effect of Vibrio on the activity of enzyme acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD) under challenge of Vibrio pathogens, and was not harmful to host according to lysozyme (LZM) activity. DH82 also ameliorated the damage to the intestine and muscles induced by V. parahaemolyticus infection according to tissue imaging. Though DH82 did present some dose-dependent adverse effects to the host, the findings revealed the effective QQ and antibacterial activity of DH82 on emerging biocontrol against V. parahaemolyticus, therefore indicating the potential application of DH82 as a biological control reagent in the sustainable and green production of aquaculture.