TABLE 3.

MICs (μg ml^–1) to polymyxins in mgrB-related and phoP-related strains of E. coli K-12 W3110.

Strain	Description	MIC to polymyxin B	MIC to colistin
W3110 pCA24N	W3110 transformed with pCA24N	0.64	0.16
W3110 ΔmgrB pCA24N	W3110 ΔmgrB transformed with pCA24N	0.64	0.16
W3110 pCA24N:mgrB	W3110 transformed with pCA24N:mgrB	0.32	0.16
W3110 ΔmgrB pCA24N:mgrB	W3110 ΔmgrB transformed with pCA24N:mgrB	0.64	0.16
W3110 ΔphoP pCA24N	W3110 ΔphoP transformed with pCA24N	0.16	0.04
W3110 pCA24N:phoP	W3110 transformed with pCA24N:phoP	0.64	0.16
W3110 ΔphoP pCA24N:phoP	W3110 ΔphoP transformed with pCA24N:phoP	0.64	0.16

Cultures were incubated overnight at 37°C on LB with 10 μM IPTG.