Dannborg, M.; Linden, S.; Thorell, K.; Bengtsson-Palme, J.

Persistent colonization by Helicobacter pylori in the stomach is connected to the development of different gastric pathologies including gastric cancer. Around half of the world's population is estimated to be colonized by H. pylori, but few develop symptoms. The bacterium dominates the gastric mucosa of individuals who are H. pylori-positive by conventional testing, however, low abundances of H. pylori have also been detected in individuals who test negative, suggesting low-level colonization The factors driving the predominance of H. pylori within the gastric microbiota remain unclear, as are its interactions with the gastric microbiota. Yet, these interaction may offer important insights into the organism's colonization success and its role in disease. In this study, we developed a gastric microbial model community, consisting of five species with high abundance and prevalence in gastric samples based on transcriptional data: H. pylori, Escherichia coli, Pseudomonas aeruginosa, Streptococcus salivarius, and Lactobacillus kalixensis. We established growth parameters and methods to track species abundance in vitro. Our results show that H. pylori growth is partly inhibited in pair-wise cultures with all other community members, except with L. kalixensis. This inhibition can to a certain extent be explained by resource competition, pH modulation of the medium, and the initial inoculum ratio of the members. The gastric microbial model community will allow dissection of the genetic mechanisms behind H. pylori interactions with other members of the gastric microbiota, and how these interactions influence H. pylori pathogenesis, providing a non-invasive, low resource model for future studies of the gastric microbiome.