Complex Interplay Between Type 1 Fimbrial Expression and Flagellum-Mediated Motility of Uropathogenic Escherichia coli

Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 48109

^* To whom correspondence should be addressed. Email: hmobley{at}umich.edu.

	Abstract

Type 1 fimbriae and flagella have been previously shown to contribute to the virulence of uropathogenic Escherichia coli (UPEC) within the urinary tract. In this study, the relationship between motility and type 1 fimbrial expression was tested for UPEC strain CFT073 by examining the phenotypic effect of fimbrial expression on motility and the effect induction of motility has on type 1 fimbrial expression. While constitutive expression of type 1 fimbriae resulted in a significant decrease in motility and flagellin expression (P<0.0001), loss of type 1 fimbrial expression did not result in increased motility. Additionally, hyper-motility and flagellar gene (over- and under-) expression were not observed to affect the expression type 1 fimbriae. Hence, it appeared that the relationship between type 1 fimbrial expression and motility is unidirectional, where the over-expression of type 1 fimbriae dramatically affects motility and flagella expression, but not vice-versa. Moreover, the constitutive expression of type 1 fimbriae in UPEC cystitis isolate, F11, and the laboratory E. coli K-12 strain MG1655, also resulted in decreased motility, suggesting that this phenomenon is not specific to CFT073 or UPEC in general. Lastly, by analyzing the repression of motility caused by constitutive type 1 fimbrial expression, it was concluded that the synthesis and presence of type 1 fimbriae at the bacterial surface is only partially responsible for the repression of motility as evidenced by the partial restoration of motility in the CFT073 fim L-ON fimA-H mutant. Altogether, these data provide further insight into the complex interplay between type 1 fimbrial expression and flagellum-mediated motility.