Multiple phases of competence occur during the Helicobacter pylori growth cycle

The gastric pathogen Helicobacter pylori undergoes genetic exchange at unusually high frequencies, primarily through natural transformation. Despite progress toward understanding the molecular mechanism of natural transformation in H. pylori, little is known about how competence is regulated or its relationship to DNA release. By measuring transformation incrementally throughout the growth curve, we show that H. pylori exhibits a novel pattern of competence with distinct peaks of transformation during both logarithmic and stationary growth phases. Furthermore, different H. pylori strains vary in the presence and timing of their competence peaks. We also examined the process of DNA release in relation to competence. Although extensive DNA release does not occur until late stationary phase, sufficient genomic DNA was present during the logarithmic phase to yield measurable transformants. These results demonstrate that the state of competence in H. pylori occurs in an unprecedented pattern during the growth curve with no clear relationship to DNA release.