In order to test the hypothesis that commensal bacteria influence the urinary odors of individuality, we collected urine from PVG and PVG.R1 male rats born by cesarian section and reared in a germ-free environment. Using the habituation-dishabituation test with PVG.RT1 (u) and Lister hooded rats as subjects, we found that urine from the germ-free rats was not discriminated, while urine from conventionally housed rats of the same strains could be discriminated (experiment 1). When the germ-free rats were moved to a conventional animal house after recolonization with commensural flora and their urine collected, it was discriminated, indicating an essential role of bacteria in determining the unique urinary odors of MHC-congenic rats (experiment 2). The conventionally housed and germ-free rats did not differ in the amount of class I antigen in their urine (experiment 3). Finally, urines of PVG and PVG.R1 donors inoculated with a defined and highly restricted flora to render them specific-pathogen-free (SPF) could not be discriminated. Urine from SPF donors moved to a conventional animal house could be discriminated (experiment 4). These results indicate that commensal bacteria are essential for the production of the unique individual odor of the urine of MHC-congenic strains of rats.
- Journal Article