TPI1 and infection: In addition to strains lacking tpiA (triose phosphate isomerase) and pgi (phosphoglucose isomerase), mutants in irreversible glycolytic steps involving both 6-carbon (pfkA; 6-phosphofructokinase transferase) and 3-carbon (pykA; pyruvate kinase) substrates were constructed and tested in competitive infections with the parental E. coli CFT073 strain.