The chemotaxis disruption of Aeromonas veronii by Lactococcus lactis and its probiotic effect on loach (Misgurnus anguillicaudatus).

Aeromonas veronii is a pathogen that is widely found in aquaculture environments. It has been observed to colonize the gastrointestinal tract of fish and other aquatic animals, with the potential to cause severe infections. Previous studies have demonstrated that probiotics, such as Lactococcus lactis 01, Lactococcus lactis 02, Enterococcus pseudoavium 03, and Bacillus sp. 04, can reduce the colonization capability of A. veronii. In this study, we sought to ascertain whether these four probiotics could affect chemotaxis by interfering with N-acyl-homoserine lactones (AHLs), thereby regulating the intestinal colonization ability of A. veronii. The findings of this study demonstrate that the extracts of L. lactis 01, L. lactis 02, and E. pseudoavium 03 significantly attenuate the chemotactic behavior of A. veronii. It is noteworthy that L. lactis 01 exhibited a substantial capacity to impede A. veronii from producing AHLs, and a preliminary investigation into substances capable of inhibiting L. lactis 01. Furthermore, we observed that L. lactis 01 can ameliorate inflammation and oxidative stress induced by A. veronii colonization in the intestinal tract of loaches. Furthermore, genome analysis of L. lactis 01 confirmed that this strain is safe for practical application. These findings lay the foundation for further research into the molecular mechanisms underlying the interactions between probiotics and pathogens, offering novel perspectives for the development of probiotic-based biocontrol strategies.