Construction of a cDNA library of Helicobacter pylori for the screening and identification of genes responsible for pathogenesis

Helicobacter pylori is a human pathogen and the major causative agent for stomach ulcers, gastritis and gastric cancer. Infection is also associated with duodenal cancer, adenocarcinoma, lymphoma, diarrhea and increased susceptibility to various infectious diseases. The aim of this study was to construct a cDNA library using RNA isolated from H. pylori, Sydney Strain (SS1). A second goal was to make available a cDNA bank for future gene expression studies. The results indicate the following: (1) a representative cDNA bank consisting of 60% recombinants ranging from 600 to 800bp in size was constructed; (2) cDNA synthesis can be successfully monitored by incorporation of biotinylated dCTP; (3) a small fraction of RNA contains polyadenylated tracts, and, finally, (4) Southern hybridization with biotinylated probes constructed from known sequences of poly A+ RNA in bacterial systems such as E. coli indicate similarities ranging from 34.4% to 77.5%. A cDNA library will provide an important resource for the study and identification of novel genes, especially those responsible for pathogenesis. It will also be an indispensable tool in elucidating the function of polyadenylated tracts in bacterial RNA.