UREASE-POSITIVE, ACID-SENSITIVE MUTANTS OF HELICOBACTER-PYLORI - UREASE-INDEPENDENT ACID RESISTANCE INVOLVED IN GROWTH AT LOW PH

Acid resistance is considered an important virulence factor of the hum an pathogen Helicobacter pylori. The enzyme urease plays an important role in this acid resistance, but there are indications that other sys tems are present. We set out to establish the relevance of these ureas e-independent acid-resistance systems for growth at low pH. Four mutan ts out of a total of 1000 UV-mutants were urease positive, grew identi cal to wild-type on pH 7 plates, but did not grow on pH 5 plates. Wher eas transformation of a mutant with its own chromosomal DNA did not re store growth at pH 5, transformation with wild-type DNA or DNA of one of the other mutants did restore the growth. From these complementatio n studies, we conclude that in H. pylori a urease-independent acid-res istance system, probably depending on the expression of more than one gene, is involved in the growth at low pH. (C) 1998 Published by Elsev ier Science B.V. All rights reserved.