Researchers Wei, Liu and Zhou developed a fluorescent D‑amino acid labeling method to track Lactobacillus strains in vivo, enabling direct imaging of probiotic colonization and persistence. The technique offers strain‑level resolution and compatibility with live imaging workflows in animal models. Study authors showed that labeled bacteria retain viability and that fluorescence enables spatial and temporal mapping of gut colonization—data that can inform probiotic formulation and dosing strategies. The method provides a tool for preclinical studies of microbial therapeutics and delivery systems.