Acid survival of Helicobacter pylori: how does urease activity trigger cytoplasmic pH homeostasis?
Kerstin Stingl1, Karlheinz Altendorf, Evert P Bakker
1Abteilung Mikrobiologie, Universität Osnabrück, D-49069, Germany. stingl@biologie.uni-osnabrueck.de
Abstract:
Helicobacter pylori can survive for several hours at pH 1 in the presence of urea. Under these conditions, the organism maintains its cytoplasmic pH at a value close to neutral. The role of the cytoplasmically located urease enzyme in this process is a matter of debate. We propose that cytoplasmic ammonia generated by the action of urease is protonated by H(+) ions leaking in from the acidic medium and that the NH(4)(+) formed is extruded from the cytoplasm via an as-yet-unidentified transport system. This mechanism is compared with the general mechanism of cytoplasmic pH homeostasis in microorganisms.
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