Assessing the Probiotic Properties and safety of Limosilactobacillus reuteri LP4 Isolated from Apis cerana Based on Whole Genome and Phenotype Analyses.

Limosilactobacillus reuteri is recognized as a GRAS organism and has been extensively applied in food, pharmaceutical, and feed industries. This study systematically investigated the probiotic properties and safety of γ-aminobutyric acid (GABA)-producing L. reuteri LP4, a strain isolated from the intestinal tract of adult Apis cerana, through comprehensive phenotypic assays and whole-genome sequencing. In vitro experiments demonstrated that strain LP4 exhibits robust tolerance to digestive fluids, strong adhesion capacity, and notable antioxidant activity. The strain demonstrated significant antagonistic effects against common gastrointestinal pathogens, including Escherichia coli K88, Staphylococcus aureus, and Salmonella typhi. Additionally, GABA synthesized by LP4 could persistently accumulate in the extracellular environment. Critically, the strain displayed no hemolytic activity and lacked the ability to synthesize biogenic amines such as cadaverine, putrescine, or agmatine. Whole-genome sequencing revealed that the LP4 genome comprises a total length of 2,552,459 bp and encodes 2455 predicted genes. Genomic annotation identified multiple probiotic-associated genes involved in antienvironmental stress, adhesion, antibacterial activity, and biosynthesis of GABA and vitamins. Importantly, no definitive virulence or antibiotic resistance genes were detected. These findings align closely with the in vitro experimental results, highlighting the exceptional probiotic potential and safety profile of LP4, establishing a foundation for its application in the food industry and human health-related fields.