TABLE 3.

Survival of the PhoU mutant and wild type E. coli strain W3110 with antibiotic exposure over timea

AntibioticTime pointNo. of bacteria (CFU/ml)
W3110PhoU mutantΔphoU
Log phaseStationary phaseLog phaseStationary phaseLog phaseStationary phase
ApStart4 × 1087 × 1093 × 1084 × 1094 × 1087 × 109
5 h3 × 1035 × 109202 × 1086 × 1026 × 108
1 day103 × 1090-11 × 1070-11 × 108
3 days01 × 1080000
5 days03 × 1070000
1 wk05 × 1060000
10 days02 × 1050000
Norf5 h1 × 1085 × 1092 × 1073 × 1085 × 1076 × 108
1 day4 × 1064 × 1094 × 1054.5 × 1071 × 1062 × 108
3 days5 × 1041 × 10802 × 10503 × 105
5 days7 × 1024 × 1060000
1 wk01.5 × 1040000
10 days02 × 1020000
  • a The susceptibilities of log phase and stationary-phase cultures of the PhoU insertion mutant (JHU-313 transposon mutant), the PhoU deletion mutant, and the wild type to ampicillin (Ap) (100 μg/ml) and norfloxacin (Norf) (3 μg/ml) were determined. CFU values were determined at different times of exposure to antibiotics for both log phase and stationary-phase cultures of the above strains. See Materials and Methods for ΔphoU deletion construction.