TABLE 1.

Urease activity in different H. pylori strains

Genotype	Urease activity (μmol NH3 min−1 mg protein−1)a
	26695		G27
	DMG	NiCl2	DMG	NiCl2
Wild type	13.55 (0.52)	20.71 (1.88)	25.76 (1.98)	36.65 (2.25)
nikR	17.64 (1.43)*	26.80 (0.89)*	29.56 (0.95)*	30.23 (0.64)**
ureE	0.11 (0.03)**	0.24 (0.07)**	0.13 (0.02)**	0.16 (0.00)**
hypA	4.76 (0.31)**	10.52 (0.53)*	0.05 (0.02)**	0.01 (0.00)**
hypB	0.09 (0.00b)**	0.23 (0.02)**	0.12 (0.00)**	0.17 (0.02)**
slyD	13.96 (0.56)	25.80 (0.58)	32.92 (2.53)*	27.00 (0.69)*
hypA slyD	0.07 (0.01)**	0.23 (0.04)**	0.01 (0.00)**	0.01 (0.00)**
ureAB	0.04 (0.04)**	0.01 (0.00)**	0.01 (0.00)**	0.01 (0.00)**
hydABC	15.21 (5.05)	25.26 (3.15)	ND	ND

^aValues are the averages for three independent cultures (standard error are in parentheses) for each strain and condition. Cells were lysed by sonication and either used directly (low activity) or diluted 20-fold (high activity) in 50 mM HEPES (pH 7.0). Samples were incubated for 10 (high activity) or 30 min (low activity) at 37°C. ND, not determined. * and **, P < 0.1 and P < 0.01 for mutant versus parent strain.

^bError is <0.01. The lowest measurable value by this method (A₆₂₅ = 0.001) corresponds to ∼0.5 to 1 nM NH₃.