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Helicobacter pylori Containing Only Cytoplasmic Urease Is Susceptible to Acid

机译：仅包含细胞质脲酶的幽门螺杆菌易受酸

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Helicobacter pylori, an important etiologic agent in a variety of gastroduodenal diseases, produces large amounts of urease as an essential colonization factor. We have demonstrated previously that urease is located within the cytoplasm and on the surface of H. pylori both in vivo and in stationary-phase culture. The purpose of the present study was to assess the relative contributions of cytoplasmic and surface-localized urease to the ability of H. pylori to survive exposure to acid in the presence of urea. Toward this end, we compared the acid resistance in vitro of H. pylori cells which possessed only cytoplasmic urease to that of bacteria which possessed both cytoplasmic and surface-localized or extracellular urease. Bacteria with only cytoplasmic urease activity were generated by using freshly subcultured bacteria or by treating repeatedly subcultured H. pylori with flurofamide (1 μM), a potent, but poorly diffusible urease inhibitor. H. pyloriwith cytoplasmic and surface-located urease activity survived in an acid environment when 5 mM urea was present. In contrast, H. pylori with only cytoplasmic urease shows significantly reduced survival when exposed to acid in the presence of 5 mM urea. Similarly,Escherichia coli SE5000 expressing H. pyloriurease and the Ni2+ transport protein NixA, which expresses cytoplasmic urease activity at levels similar to those in wild-typeH. pylori, survived minimally when exposed to acid in the presence of 5 to 50 mM urea. We conclude that cytoplasmic urease activity alone is not sufficient (although cytoplasmic urease activity is likely to be necessary) to allow survival of H. pyloriin acid; the activity of surface-localized urease is essential for resistance of H. pylori to acid under the assay conditions used. Therefore, the mechanism whereby urease becomes associated with the surface of H. pylori, which involves release of the enzyme from bacteria due to autolysis followed by adsorption of the enzyme to the surface of intact bacteria (“altruistic autolysis”), is essential for survival of H. pylori in an acid environment. The ability of H. pylori to survive exposure to low pH is likely to depend on a combination of both cytoplasmic and surface-associated urease activities.
机译：幽门螺杆菌（Helicobacter pylori）是多种胃十二指肠疾病的重要病原体，会产生大量脲酶，作为必需的定植因子。先前我们已经证明脲酶位于细胞质内和H的表面上。体内和固定相培养中的幽门螺杆菌本研究的目的是评估细胞质和表面定位的脲酶对 H能力的相对贡献。幽门螺杆菌在尿素存在下暴露于酸中存活下来。为此，我们比较了 H的体外耐酸性。幽门螺杆菌细胞仅具有细胞质脲酶，而细菌既具有细胞质脲酶，又具有表面局部或细胞外脲酶。通过使用新鲜的传代培养细菌或通过反复传代培养的 H产生仅具有胞质脲酶活性的细菌。幽门螺杆菌与氟尿酰胺（1μM），一种有效的但难扩散的脲酶抑制剂。 H。当存在5 mM尿素时，具有胞质和表面定位的尿素酶活性的幽门螺杆菌在酸性环境中可以存活。相反， H。在5 mM尿素存在下暴露于酸性条件下，仅具有胞质尿素酶的幽门螺杆菌显示存活率显着降低。同样，表达 H的大肠杆菌 SE5000。幽门螺杆菌尿素酶和Ni 2 + 转运蛋白NixA，其表达细胞质脲酶活性的水平与野生型 H相似。在5至50 mM尿素存在下暴露于酸中时，幽门螺杆菌存活最少。我们得出的结论是，仅胞质脲酶活性不足以允许 H存活（尽管胞质脲酶活性可能是必需的）。幽门螺杆菌表面定位的脲酶的活性对于 H的抗性至关重要。幽门螺杆菌在所使用的测定条件下转化为酸。因此，脲酶与 H的表面结合的机理。幽门螺旋杆菌涉及由于自溶作用而从细菌中释放出酶，然后将酶吸附到完整细菌的表面（“利他自溶作用”），对 H的生存至关重要。酸性环境中的幽门螺旋杆菌。 H的能力。幽门螺杆菌能否在低pH值条件下存活下来，可能取决于细胞质和表面相关脲酶活性的结合。

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