The bacterium that causes ulcers and contributes to stomach cancers uses a clever interaction between two genes to randomly tighten and loosen its grip on the stomach, according to a study by researchers at Washington University School of Medicine in St. Louis and Umeå University in Sweden. Helicobacter pylori often binds tightly to cells of the stomach lining to feed, but the newly identified interaction ensures that a small reservoir of bacteria are always more loosely connected. This reservoir is much more likely to survive if the host mounts a strong immune response.