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Hannover Medical School

A "Chameleon" in the Stomach

Scientists at the Hannover Medical School have investigated the rapid adaptability of the gastric cancer pathogen Helicobacter pylori.

Two men and a woman in white coats © MHH/Kaiser

Professor Dr. Sebastian Suerbaum with the doctoral student Iratxe Estibariz and the postdoctoral Dr. Florent Ailloud.

Helicobacter pylori, a gastric cancer-causing bacterium, is able to adapt to the human body in such a way that it becomes as individual as a human fingerprint: like any other bacterium, it varies its genes during infection.

Reasons for Genetic Variability Investigated

Scientists from the Hannover Medical School (MHH), together with the statistical expert Dr. Xavier Didelot from the Imperial College in London, have found the reason for this great variability. It was already known that two different Helicobacter pylori bacteria exchange DNA fragments when they meet in the stomach. It has now been shown that the great individuality is due to the fact that there are two absorption mechanisms which lead to the integration of fragments of different lengths: "The recording of very short DNA-pieces, which are less than 50 base pairs long, allows the bacteria to have an extremely high variability within the genes. The inclusion of longer DNA fragments (on average consisting of 1,600 base pairs) ensures constancy and the possibility to exchange whole genes.The effect of the genome exchange is similar to that of sexually reproducing organisms", explains Professor Dr. Sebastian Suerbaum. The head of the MHH Institute for Medical Microbiology and Hospital Hygiene aims to trace the underlying molecular mechanisms. He was able to elucidate one mechanism: Helicobacter pylori possesses many so-called restriction enzymes, which intersect penetrating alien DNA. However, the absorbed pieces of DNA from other Helicobacter pylori bacteria are integrated into the genome regardless of these enzymes. The researchers published the results in the prestigious journal "Nature Communications".

Problems for Vaccine Development

The enormous genetic variability of Helicobacter pylori is also considered an important obstacle to the development of a vaccine against this pathogen. This is an important motivation for the researchers whose work is funded within the framework of the German Center for Infection Research (DZIF) and the Collaborative Research Center (SFB) 900.

About 40 Percent of Germans Infected

About 40 percent of the German population are chronically infected with Helicobacter pylori. It can, among other things, cause gastric ulcers and is responsible for most casas of stomach cancer. Recently, it could be demonstrated that patients with a Helicobacter pylori infection who are treated are less likely to get stomach cancer than untreated patients. Therefore, the recommendations for the treatment of the gastric cancer virus have been significantly expanded.

(Published on 7. July 2016)