New Insight:To get successful complementation and expression of your proteinof interest in H. pylori, it is necessary to grow single colony from the transformants and propagate it to grow pure cultures. Following growth of pure culture expression of complemented protein could be screened. Growing mixed population of H. pylori after transformation may lead to unsuccessful expression of the protein of interest. This may be due to the reason that non expressing bacterial colonies growth over could dominate the actual expressing colonies.