Identification of environmental stress-regulated genes in Helicobacter pylori by a lacZ reporter gene fusion system

Background. Helicobacter pylori persists in the human stomach for decades. This requires an efficient adaptation of H. pylori to the gastric niche and involves the regulation of bacterial genes in response to environmental stress. Efficient molecular tools to identify regulated H. pylori genes are scarce, therefore we developed a genomic 1acZ reporter gene fusion system in H. pylori to screen for stress-regulated genes. Materials and methods. The integration vector pBW was constructed and used to generate random genomic 1acZ fusions in H. pylori. Two-hundred-and-fifty, H. pylori transformants were selected from this library, replica-plated and screened for differential lacZ expression after exposure to two environmental stress conditions: increased temperature (42 degreesC), and iron-limitation. Results. From a library of H. pylori transformants,with random genomic transcriptional lacZ fusions, two stress-regulated H. pylori loci were identified. The transcription of a gene of unknown function (designated hsp12) was increased by incubation at 42 degreesC. The transcription of a locus, consisting of the three fumarate reductase subunit genes (frdCAB) and the HPO190 gene from H. pylori strain 26695, was decreased under iron-limitation. Conclusions. This is the first time that a genomic transcriptional lacZ reporter gene H. pylori library has been used as a tool for the fast and efficient identification of environmental stress-regulated H. pylori genes.