TABLE 3.

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

Antibiotic	Time point	No. of bacteria (CFU/ml)
		W3110		PhoU mutant		ΔphoU
		Log phase	Stationary phase	Log phase	Stationary phase	Log phase	Stationary phase
Ap	Start	4 × 108	7 × 109	3 × 108	4 × 109	4 × 108	7 × 109
	5 h	3 × 103	5 × 109	20	2 × 108	6 × 102	6 × 108
	1 day	10	3 × 109	0-1	1 × 107	0-1	1 × 108
	3 days	0	1 × 108	0	0	0	0
	5 days	0	3 × 107	0	0	0	0
	1 wk	0	5 × 106	0	0	0	0
	10 days	0	2 × 105	0	0	0	0
Norf	5 h	1 × 108	5 × 109	2 × 107	3 × 108	5 × 107	6 × 108
	1 day	4 × 106	4 × 109	4 × 105	4.5 × 107	1 × 106	2 × 108
	3 days	5 × 104	1 × 108	0	2 × 105	0	3 × 105
	5 days	7 × 102	4 × 106	0	0	0	0
	1 wk	0	1.5 × 104	0	0	0	0
	10 days	0	2 × 102	0	0	0	0

^aThe 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.