Research Progress on the Effect of Bacillus velezensis on Disease Resistance of Aquatic Animals.

With the rapid expansion of intensive aquaculture, the frequent outbreak of diseases and the overuse of antibiotics have become increasingly critical issues. Therefore, developing green and efficient antibiotic alternatives is essential for the sustainable growth of the industry. As a novel probiotic, Bacillus velezensis has shown great potential in improving the disease resistance of aquatic animals, owing to its excellent spore-forming ability, broad-spectrum antibacterial activity, and immunoregulatory functions. This paper systematically reviews the main mechanisms by which B. velezensis enhances disease resistance in aquatic animals, including directly inhibiting pathogens through the secretion of various lipopeptides and polyketides such as surfactin, iturin, and fengycin; interfering with pathogen quorum sensing systems via quorum quenching enzymes, thereby suppressing virulence factor expression and biofilm formation; modulating intestinal microbiota structure to increase the abundance of beneficial bacteria while reducing pathogenic proliferation; and activating the non-specific immune system of the host to upregulate immune-related indicators such as acid phosphatase, superoxide dismutase, and key cytokines (such as IL-1β, TNF-α). In addition, this review summarizes the application effects of B. velezensis on improving aquaculture water quality and promoting host growth. Furthermore, the potential ecological impacts on natural microbial communities and strain-dependent biosafety risks are evaluated. Finally, current research limitations-such as strain-specific functional differences, insufficient in-depth analysis of mechanisms, and inconsistent application outcomes-are discussed. Future prospects for promoting the efficient and stable application of B. velezensis in aquaculture through strategies including gene editing, multi-omics integration, and precise formulation compounding are also proposed.