ACID-INDUCED EXPRESSION OF AN LPS-ASSOCIATED GENE IN HELICOBACTER-PYLORI

To investigate urease-independent mechanisms by which Helicobacter pyl ori resists acid stress, subtractive RNA hybridization was used to ide ntify H. pylori genes whose expression is induced after exposure to ac id pH. This approach led to the isolation of a gene that encoded a pre dicted 34.8 kDa protein (WbcJ), which was homologous to known bacteria l O-antigen biosynthesis proteins involved in the conversion of GDP-ma nnose to GDP-fucose, An isogenic wbcJ null mutant strain failed to exp ress O-antigen and Lewis X or Lewis Y determinants and was more sensit ive to acid stress than was the wild-type strain. Qualitative differen ces in LPS profiles were observed in H. pylori cells grown at pH 5 com pared with pH 7, which suggests that H. pylori may alter its LPS struc ture in response to acidic pH. This may be an important adaptation fac ilitating H. pylori colonization of the acidic gastric environment.