HpaA shows variable surface localization but the gene expression is similar in different Helicobacter pylori strains

Due to earlier contradictory results regarding the localization of the puta tive Helicobacter pylori adhesin A (HpaA), we aimed to compare the gene and protein expression and surface localization of HpaA in different H. pylori strains. Five H. pylori strains were cultivated for 11 days and analysed b y Northern blot analysis, flow cytometry (FCM), semi-quantitative dot blot, colony blot, immuno-electron microscopy (IEM), and phase-contrast microsco py. The highest transcriptional activity of the hapA gene as observed after 3-4 days of cultivation and two mRNA transcripts of 1600 and 3100 nucleoti des, respectively, were detected in all five strains with the hpaA probe. W e also showed by reverse transcription-polymerase chain reaction (RT-PCR) t hat the hpaA gene is co-transcribed with the downstream omp18 gene. The hig hest total HpaA protein production in bacteria occurred between day 3 and 7 , as determined by semi-quantitative dot blot, and was similar in the diffe rent strains. The maximal proportion of cells with HpaA on the bacterial su rface, detected by FCM, was for strain SS1, 90%; Hel 344, 60%; CCUG 17875, 61%; CCUG 17874, 86% and for strain AH 244 only 35%. By IEM HpaA was detect ed in all strains both on the bacterial surface and on the flagellar sheath . (C) 2001 Academic Press.