Vitamin B6 form produced by Lactobacillus induces metabolic disorder and suppresses multi-pathogenic bacteria

Vitamin B₆ comprises six vitamers, pyridoxal, pyridoxine, pyridoxamine, pyridoxal 5'-phosphate (PLP), pyridoxine 5'-phosphate (PNP), and pyridoxamine 5'-phosphate (PMP), recognized for pleiotropic functions in mitigating oxidative stress and modulating metabolic homeostasis. This study reveals that PMP exhibits broad-spectrum antibacterial activity against pathogens, including Aeromonas hydrophila (A. hydrophila), Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella. In vitro assays demonstrated that high-dose PMP disrupts bacterial membrane integrity, triggering extensive extracellular DNA leakage and bactericidal effects. Furthermore, we identified Pediococcus acidilactici GR-6 and Lactobacillus fermentum GR-7, isolated from crucian carp gut, that synergistically synthesize vitamin B₆ de novo during pathogens co-culture, achieving ≥63% inhibition of polymicrobial pathogens. Integrated genomic, proteomic and metabolomic analyses confirm that GR-6/GR-7 consortium regulates pyridoxal kinase and pyridoxine 4-dehydrogenase, maintaining vitamin B₆ primarily as pyridoxine (84%) and PMP (16%). In A. hydrophila-infected crucian carp, dietary supplementation with GR-6/GR-7 consortium increases survival by 50%, with restored gut microbiota diversity and attenuated systemic inflammation (Alkaline phosphatase, Lysozyme and GSH/GSSG ratio). Metabolomics showed that probiotics-mediated elevation of intestinal content PMP level directly inhibits A. hydrophila infection. Collectively, this study establishes PMP as a novel probiotic metabolite that directly eliminates pathogens and resolving gut microbiome-host metabolic dysregulation.