Probiotic Characterization of a Novel Enterococcus faecium CPU2401 from Pickles: Unraveling Genomic Mechanisms Underlying the Combating of Oxidative Stress and Infection.

Enterococcus faecium CPU2401, isolated from traditional pickles, was assessed for its probiotic potential through an integrated approach combining whole-genome sequencing and phenotypic assays. The complete genome (2,803,294 bp) comprises a chromosome (2,724,439 bp) and a plasmid (78,855 bp), with a GC content of 38.38% and 2,786 predicted genes. Genomic analysis revealed the presence of various resistance genes (e.g., optrA, efmA) and numerous genes involved in secondary metabolite synthesis, such as carbohydrate-active enzymes (CAZymes). Phenotypically, E. faecium CPU2401 exhibited high gastrointestinal tolerance, with survival rates of 55.4% at pH 4 and 86.7% in the presence of 0.1% bile salts. It also showed good antioxidant capacity, scavenging 3.83% of DPPH, 22.0% of hydroxyl, and 83.4% of superoxide anion radicals, together with notable antibacterial activity against pathogens including Salmonella Typhimurium and Staphylococcus aureus. In Caenorhabditis elegans, E. faecium CPU2401 enhanced resistance to S. Typhimurium infection and significantly extended lifespan by 22.4% compared to the control. These findings underscore the strain's promise as a probiotic candidate for functional food and health applications.