Table 3.

Effect of the constitutive expression of amtB on growth of an S. typhimurium gltB mutant strain at different pH values and ammonium concentrations

Strain	[NH4+],* mM	pH 7			pH 6
		5	1	0.5	5	1	0.5
SK2633		57	58	63	60	65	66
(wild type)
SK3390		62	63	62	65	68	64
(wild type/Ptac-amtB)
SK3062		65	105	160	111	700	≈1,130
(gltB†)
SK3391		68	106	160	105	360	450
(gltB/Ptac-amtB)
SK3109		60	63	68	66	115	142
(gltB gdhp515)
SK3392		64	68	69	70	88	108
(gltB gdhp515/Ptac-amtB)

Data are doubling time (min). Cells were grown in N⁻C⁻ medium with glucose as carbon source and ammonium as sole nitrogen source. The glucose concentration was 0.4% at 5 mM ammonium and 0.2% at lower ammonium concentrations. Isopropyl β-d-thiogalactoside was present at 1 mM. 

^*[NH₄⁺ + NH₃]. 

^†The lesion is ΔgltB824 (31).