Expressed Proteome of Extraintestinal Escherichia coli Associated with Urinary Tract Infections

Extraintestinal pathogenic Escherichia coli (ExPEC) have a capacity to cause serious infections of blood, the central nervous system and particularly the urinary tract. Relatively little is known about how ExPEC adapt their cell-wide protein expression to environments with different carbon sources and other required nutrients. We used label-free quantitative (LFQ) proteomic analysis to determine proteomes of five ExPEC strains purified from clinical blood cultures, and compared them with proteomes of reference uropathogenic E. coli strain 536 derived from blood culture and two chemically different solid media. We identified 2,883 proteins in total, and for 90% of the detected proteins described their relative quantitative levels based on LFQ intensity scores. Comparison of anaerobic and aerobic blood cultures revealed significant differences in the levels of 32 proteins out of 1854 shared proteins. A majority of these proteins was associated with acquisition and utilization of metal ions, which are critical either for anaerobic (nickel) or aerobic (iron) respiration. ANOVA analysis of the relative quantitative levels of 1758 proteins shared between the strains identified 47 differentially expressed proteins, including proteins involved in vitamin B6 metabolism, cell motility and virulence. Comparison of strain 536 proteomes derived from blood cultures and solid media showed substantial variation in the relative quantitative levels of 200 proteins, which represented 11% of the common proteins between the conditions. Blood culture condition was characteristic by upregulation of anaerobic fermentative metabolism, cell motility and iron utilization. In a response to the growth on solid media increased levels of proteins functional in aerobic respiration, catabolism of various biochemicals obtained from the media and protection against environmental stresses. The study presents the largest coverage of ExPEC/UPEC proteome to date,with a detail account of ExPEC metabolism under three chemically different environments.