Contact with host cells induces a DNA repair system in pathogenic Neisseriae

DNA repair systems play a major role in maintaining the integrity of bacterial genomes. Neisseria meningitidis, a human pathogen capable of colonizing the human nasopharynx, possesses numerous DNA repair genes but lacks inducible DNA repair systems such as the SOS response, present in most bacteria species. We recently identified a set of genes upregulated by contact with host cells. An open reading frame having high homology with the small subunit of Escherichia coli exonuclease VII (xseB) belongs to this regulon. The increased sensitivity of a mutant in this coding sequence to UV irradiation, alkylating agent and nalidixic acid demonstrates the participation of this gene in meningococcal DNA repair. In addition, the upregulation of the transcription of this open reading frame upon interaction of N. meningitidis with host cells increased not only the bacterial ability to repair its DNA but also the rate of phase variation by frameshifting. Together these data demonstrate that N. meningitidis possesses an inducible DNA repair system that might be used by the bacteria to adapt to its niches when it is colonizing a new host.