Figure 4

Aerobic citrate utilization by different ExPEC bacteria on Simmon’s plates when a co-substrate (glucose) is provided. All conditions, i.e., days (d), temperature (°C) and percentage of glucose added (%), are stated in the upper corner of the subfigures. (a) Citrate utilization by different E. coli groups, i.e., NMEC (IHE3034, IHE3034F and RS218), UPEC (UTI89 and 536), compared to that of the commensal MG1655. (b) Reconstitution of citrate uptake signalling events in the uropathogenic E. coli K1 strain UTI89. The wild-type UTI89 strain did not utilize citrate, while its RpoS-deficient variant (UTI89∆rpoS) showed positive results compared to those of IHE3034 and IHE3034 ∆ycgG2. (c) UTI89 and UTI89∆rpoS bacteria tested for citrate utilization in the presence of 0.1% glucose at 37 °C (Box I) and at 22 °C (Box II). (d) The 536 pyelonephritis isolate, its less virulent derivatives, 536∆102 and 536R3, and its avirulent derivative, 536-21, were tested for citrate utilization. The 536-21 derivative tested negative, but its ∆rpoS mutant was positive for citrate utilization (marked with black box), while the 536R3∆rpoS strain still tested positive for citrate, like its parental strain. (e) Different pyelonephritis clinical isolates tested for citrate utilization (Box I) and for haemolysis (Box II).