TABLE 6.

Survival of the deletion mutants ΔphoB, ΔphoR, and ΔphoBR with antibiotic exposure

Time of exposure to Ap	No. of bacteria (CFU/ml)
	W3110		ΔphoB		ΔphoR		ΔphoBR		ΔphoU		ΔhipA
	Log phase	Stationary phase	Log phase	Stationary phase	Log phase	Stationary phase	Log phase	Stationary phase	Log phase	Stationary phase	Log phase	Stationary phase
Start CFU	3.7 × 108	8 × 109	1 × 108	6 × 109	1 × 108	7 × 109	1 × 108	5 × 109	1 × 108	1 × 109	2 × 108	7 × 109
5 h	9 × 103	6 × 109	6 × 103	4 × 109	1 × 103	4 × 109	7 × 103	3 × 109	1 × 102	2 × 108	1 × 104	6 × 109
24 h	1 × 102	2 × 109	1 × 102	1.8 × 109	1 × 102	1.5 × 109	2 × 103	1.7 × 109	0	7 × 106	1 × 103	1.8 × 109
72 h	0	2 × 108	0	1 × 108	0	1 × 108	0	2 × 108	0	0	0	1 × 108

The susceptibilities of log phase and stationary phase cultures of the deletion mutants ΔphoB, ΔphoR, ΔphoBR, ΔphoU, and ΔhipA and the wild type to ampicillin (Ap) (100 μg/ml) were determined. CFU values were determined at different times of exposure.