Identification, Characterization, and Probiotic Potentials of Lactobacillus pentosus SF-1

In recent years probiotics have been considered as a potential substitution of antibiotics to control pathogens and treat infectious diseases in aquaculture. In the present study a strain of Lactobacillus pentosus, named as L. pentosus SF-1, was isolated from waters in aquaculture. The species identification of this strain was conducted by 16S rRNA sequence, and the physiological and biochemical characteristics of this strain were assessed. Furthermore, the virulence, antibiotic sensitivity, cell surface characteristics and acid/base-resistance of L. pentosus SF-1 were determined to evaluate the probiotic potentials of this strain. Specifically, L. pentosus SF-1 is sensitive to most common antibiotics, and no hemolysin was generated from it, indicating the safety of this strain to hosts. In addition, L. pentosus SF-1 was able to tolerate the artificial gastric juice at pH 3 for 4 h and the artificial intestinal fluid at pH 6.8 or 8.0 for 6 h. Moreover, the analysis of self-aggregation and the adhesion of L. pentosus SF-1 to organic solvents suggested a high potential of L. pentosus SF-1 to inhabit the hosts, which was confirmed by testing the colonization of L. pentosus SF-1 in germ-free zebrafish. Interestingly, L. pentosus SF-1 displayed a high bactericidal activity against several bacterial pathogens. Consistently, the incubation of L. pentosus SF-1 significantly promoted the expression of antimicrobial components in zebrafish, contributing to the protection of the fish from E. tarda infection in vivo. Taken together, the probiotic strain L. pentosus SF-1 could be applied as anti-infection reagent in aquaculture.