Recombination-Based In Vivo Expression Technology Identifies Helicobacter pylori Genes Important for Host Colonization

Here we undertook to identify colonization and gastric disease-promoting factors of the human gastric pathogen Helicobacter pylori as genes that were induced in response to the stomach environment. Using recombination-based in vivo expression technology (RIVET), we identified six promoters induced in the host compared to laboratory conditions. Three of these promoters, designated P ivi10 , P ivi66 , and P ivi77 , regulate genes that H. pylori may use to interact with other microbes or the host. P ivi10 likely regulates the mobA , mobB , and mobD genes, which have potential roles in horizontal gene transfer through plasmid mobilization. P ivi66 occurs in the cytotoxin-associated gene pathogenicity island, a genomic region known to be associated with more severe disease outcomes, and likely regulates cagZ , virB11 , and virD4 . P ivi77 likely regulates HP0289, an uncharacterized paralogue of the vacA cytotoxin gene. We assessed the roles of a subset of these genes in colonization by creating deletion mutants and analyzing them in single-strain and coinfection experiments. We found that a mobABD mutant was defective for murine host colonization and that a cagZ mutant outcompeted the wild-type strain in a coinfection analysis. Our work supports the conclusion that RIVET is a valuable tool for identifying H. pylori factors with roles in host colonization.