Integrative genomic and functional characterization of a feline milk–derived Lactiplantibacillus plantarum MNN reveals host-specific adaptation and ecological safety

Feline milk serves as a natural reservoir of host-adapted microorganisms that shape early-life gut microbiota and immune development. Our previous work identified <i>Pediococcus acidilactici</i> M22 from feline milk, which showed robust gastrointestinal tolerance, antioxidant capacity, and safety, providing the first evidence that feline milk-derived probiotics could be suitable for simulated pet milk formulations. However, <i>P. acidilactici</i> species possess limited genomic versatility and metabolic adaptability, warranting exploration of other lactic acid bacteria with broader functional repertoires. MNN exhibited superior acid and bile tolerance (99.83% survival at pH 2.5 and 88% at 0.3% bile) compared with M22 (59.93 and 84.38%, respectively), indicating enhanced gastrointestinal resilience. It demonstrated notable antioxidant capacity (DPPH 52.64%, ABTS 55.59%, superoxide 63.17%) and increased serum SOD and GSH while reducing MDA in mice, reflecting a stronger antioxidative defense than M22, whose effects were primarily systemic. Genome sequencing revealed a 3.29 Mb chromosome-1.23 Mb larger than M22-harboring 3,091 coding sequences enriched in stress response (<i>groEL, dnaK, trxA</i>), antioxidant (<i>katA, gshA</i>), and antimicrobial (<i>plnE</i>, <i>plnF</i>) genes, as well as expanded membrane transport and carbohydrate metabolism pathways. Unlike M22, MNN also preserved gut microbial homeostasis <i>in vivo</i>, maintaining <i>α</i>/<i>β</i> diversity and subtly enriching beneficial genera (<i>Oscillibacter, Adlercreutzia</i>) without dysbiosis. Functional prediction confirmed stable carbohydrate and amino acid metabolism, with no enrichment of resistance or virulence genes. Compared with <i>P. acidilactici</i> M22, <i>L. plantarum</i> MNN exhibits higher genomic plasticity, stronger antioxidative capacity, and distinct ecological compatibility, marking a functional transition from "safety-verified probiotic" to "host-adapted microbiota-stabilizing probiotic." Integrating genomic, functional, and ecological analyses, this study identifies MNN as a next-generation probiotic candidate for enhancing intestinal homeostasis and antioxidant defense in companion animals.