Fig 1.

Urease activity in intact organisms and total urease activity. (A) H. pylori wild type and ΔarsS were incubated for 30 min in strong buffers of various pHs with [¹⁴C]urea, and the liberation of [¹⁴C]O₂ was measured (n = 3). Like the wild type, the ΔarsS strain shows acid activation of cytoplasmic urease mediated by UreI, with minimal activity at a neutral pH and increasing activity with decreasing medium pHs, with maximal activity below pH 5.5. (B) The urease activity of H. pylori wild-type and ΔarsS lysates was measured in strong buffer at pH 7.4. In agreement with the curve shown in panel A, the level of total urease activity is lower in the absence of ArsS (n = 3).