Nutritional and Appendage Requirement for Surface Motility of Non-Pathogenic and Uropathogenic Escherichia Coli

Abstract

Urinary tract infections (UTIs) are one of the most common bacterial infections, affecting approximately 150 million people worldwide each year and uropathogenic Escherichia coli is the most common causative pathogen. E. coli is a gram-negative bacterium that resides in the intestines as a commensal but can become an opportunistic pathogen in the urinary tract. Flagellamediated motility is essential for virulence and colonization for ascending tract UTIs. However, E. coli can also move on a surface with pili. Understanding motility and its requirements are necessary for understanding UTIs and are potentially important for treatment. This study had two main objectives. The first objective was to compare the surface motility of nonpathogenic E. coli (NPEC) and uropathogenic E. coli (UPEC) strains. NPEC strains exhibited either a slow, fimbriae/pili-dependent movement or a fast flagella-dependent motility. NPEC-fast strains had an insertion sequence (IS) element in the flhDC promoter region — flhDC codes for the master regulator of flagella gene synthesis and the IS element increases expression of flhDC and flagellar genes. In UPEC strains, flagella synthesis was high, but the flhDC promoter region did not have an IS element. The unusual aspect of flagella-dependent motility in UPEC strains is that the medium used for assaying motility contains glucose, and glucose inhibits cAMP synthesis which is required for flagella synthesis. In the UPEC strain UTI89, flagella synthesis required cAMP, which suggests that glucose does not control cAMP synthesis. In the NPEC-fast strains, the IS element presumably bypasses the glucose and cAMP control of flagella synthesis. The different glucose effects could suggest metabolic differences between NPEC and UPEC strains. The second objective was to examine the metabolic requirements for surface motility in these strains. The glucose concentration as well as the pathway requirements for surface motility were different for pili-dependent NPEC and flagella-dependent UPEC. The pili-dependent parental NPEC strain, W3110, required the Embden-Meyerhof-Parnas pathway of glycolysis, but UTI89 did not; instead, UTI89 required the Entner-Doudoroff glycolytic pathway. Conversely, UTI89 required acetogenesis and the TCA cycle for motility, but W3110 did not. In addition, UTI89 motility required an aldolase with no known function, which suggests an alternate route for carbohydrate metabolism. In summary, the metabolic requirements for motility in uropathogenic UTI89 differ from their NPEC counterparts. The UPEC pattern of metabolism could be a specific adaptation to the urinary tract/bladder environment and thus hold immense value in understanding ascending urinary tract infections.