The uropathogenic Escherichia coli strain CFT073 has multiple iron
acquisition systems, including heme and siderophore transporters. A
tonB mutant derivative of CFT073 failed to use heme as an iron source
or to utilize the siderophores enterobactin and aerobactin, indicating
that transport of these compounds in CFT073 is TonB dependent. The
TonB
derivative showed
reduced virulence in a mouse model of urinary tract infection.
Virulence was restored when the tonB gene was introduced on
a plasmid. To determine the importance of the individual TonB-dependent
iron transport systems during urinary tract infections, mutants
defective in each of the CFT073 high-affinity iron transport systems
were constructed and tested in the mouse model. Mouse virulence
assays indicated that mutants defective in a single iron transport
system were able to infect the kidney when inoculated as a pure
culture but were unable to efficiently compete with the wild-type
strain in mixed infections. These results indicate a role for TonB-dependent
systems in the virulence of uropathogenic E. coli strains.
