Helicobacter pylori chronically colonises approximately half of the world’s population. Trans​mission between humans is thought to occur via person-to-person contact during childhood. Persistent infection is usually asymptomatic but can evolve in peptic ulcer disease and gastric cancer. Eradication treatments are based on antibiotics utilization, but during the last decades, H. pylori antibiotic resistance has increased dramatically. Up to 30% of patients are not cured after completing their first course of treatment. This augmentation, as well as the success in infection can be explained by the high adaptability of these bacteria. H. pylori is indeed one of the most genetically diverse bacteria and comparison of the sequenced genomes reveals an amazing variability between strains. This genomic variability is the result of high mutation rates, high recombination efficiency, and natural competence, which allows constant and rapid spread of new mutation among the bacterial population. There is therefore a critical balance between the maintenance of the genetic information and the capacity to adapt. 

Since 1999 our laboratory has contributed to the understanding of the DNA metabolism processes defining the genomic plasticity of H. pylori. Initially, the group has analysed both, biochemically and genetically, the Base Excision Repair pathway, unveiling a new family of DNA glycosylases. Since 2005, the LRIG has turned its attention to the study of Homologous Recombination (HR) in H. pylori allowing the identification of missing components of the mediator complexes responsible for the formation of an active RecA nucleofilament. Homologous recombination being the last step required for the integration of exogenous DNA into the bacterial chromosome, the LRIG has also extended its interests to the analysis of natural transformation in this pathogen. H. pylori presents several important differences with the other competent bacteria starting by the proteins involved in its transport across the two membranes to the fact that in this species natural competence is constitutive. By combining genetics, biochemistry and cell biology approaches we aim at understanding the molecular mechanisms by which the incoming DNA is processed first during its passage through the periplasm and then in the cytoplasm to recombine with the host genome. ​