Temporal Regulation of Genes in Uropathogenic during Infection of the Murine Urinary Tract.

Uropathogenic (UPEC) adhere to cells in the human urinary tract via type 1 pili that undergo phase variation where a 314-bp DNA element flips between Phase-ON and Phase-OFF orientations through two site-specific recombinases, FimB and FimE. Three operon transcriptional fusions were created and moved into the clinical UPEC isolate NU149 to determine their temporal regulation in UPEC growing in the urinary tract. Within murine urinary tracts, the UPEC strains demonstrated elevated transcription of and early in the infection, but lower transcription by the fifth day in murine kidneys. In contrast, transcription was much lower than either or early, increased markedly at 24 h after inoculation, and then dropped five days after inoculation. Positioning of was primarily in the Phase-ON position over the time span in UPEC infected bladders, whereas in UPEC infected murine kidneys the Phase-OFF orientation was favored by the fifth day after inoculation. Hemagglutination titers with guinea pig erythrocytes remained constant in UPEC growing in infected murine bladders but fell substantially in UPEC infected kidneys over time. Our results show temporal regulation of gene expression in different environmental niches when UPEC infects the murine urinary tract.