Biotin-labeled plasmid DNA probes for detection of epithelium-associated strains of lactobacilli.

Biotin-labeled DNA probes prepared from whole plasmids (5.5 and 4.8 kilobases) of two lactobacillus strains (Lactobacillus delbrueckii 21 and Lactobacillus reuteri 100-23) were used to detect the homologous bacteria in microtome-cryostat-prepared sections of murine forestomach. The forestomach sections were incubated on nylon filter membranes placed on agar plates and, after lysis of the lactobacillus cells and denaturation of their DNA, were used in hybridization experiments with the strain-specific DNA probes. Hybridization of the probes to membranes containing sections from lactobacillus-free mice did not occur. The probes detected the presence of homologous strains of lactobacilli in sections cut from the forestomach of mice harboring one or both of the strains.