Figure 1.

AFLP analyses demonstrates that phase variation in oipA in vitro is infrequent. Fluorescently labeled amplicons containing the poly CT repeat tract of oipA in both cag positive (26695) and cag PAI negative (J68) strains of H. pylori demonstrate relatively minor levels of variation in length, indicating that the expression phase status of oipA is quite stable when H. pylori is grown in vitro. Bars represent the mean ± standard deviation calculated using three biological replicates. Amplification of a similar sized amplicon from a non-repeat bearing region of oipA, as a PCR control, revealed no fragment polymorphisms (data not shown).