B-175. Molecular Characterization of PapX, a P Fimbrial-Encoded Inhibitor of Motility in Uropathogenic Escherichia coli
Motility and adherence are two integral aspects of bacterial pathogenesis. Adherence, often mediated by fimbriae, permits bacteria to attach to host cells and establish infection, whereas flagellum-driven motility allows bacteria to disseminate to sites more advantageous for colonization. Both fimbriae and flagella have been proven important for the virulence of uropathogenic Escherichia coli (UPEC). Reciprocal regulation is one mechanism by which bacteria may reconcile the contradictory actions of adherence and motility. PapX, a P fimbrial gene product of UPEC strain CFT073, has previously been shown to be a functional homolog of MrpJ of Proteus mirabilis; ectopic expression of PapX in P. mirabilis leads to a reduction in motility. To define the connection between P fimbriae expression and motility in UPEC, the role of papX in the regulation of motility of UPEC strain CFT073 was examined. Overexpression of papX decreased the motility of CFT073, which correlated with a significant reduction in flagellin protein synthesized. Conversely, an increase in motility and flagellin production was seen in an isogenic papX deletion mutant of CFT073. Microarray and qRT-PCR analysis indicated that the repression of motility of CFT073 by PapX appears to occur during transcription; expression of many motility-associated genes, including flhDC, the master regulator of motility, is decreased when papX is overexpressed or is increased in the papX deletion mutant compared to wild type. We conclude that synthesis of P fimbriae feeds back on flagella synthesis and represses motility via PapX.