Genetic exchange between Escherichia coli strains in the mouse intestine.

Germ-free mice contaminated with selected Escherichia coli strains were used for experiments designed to demonstrate gene transfer and recombinant formation in vivo. The well-characterized conjugation system of E. coli K-12 was examined in these experiments. Contamination of germ-free mice with a polyauxotrophic F(-) strain followed by the addition of isogenic Hfr, F', or F(+) strains resulted in the appearance of all recombinant classes at frequencies that would be expected from an in vitro mating experiment. Inheritance of unselected donor markers occurred at frequencies that were dependent on linkage relationships established in experiments in vitro. The presence of Lactobacillus had no influence on gene transfer and recombinant formation in an F' x F(-) in vivo mating. The R factor ROR-1 was transferred from E. coli strain M7-18 to an E. coli F(-) strain in the mouse intestine.