Differential Distribution of Novel Restriction-Modification Systems in Clonal Lineages of Neisseria meningitidis

ABSTRACT Using representational difference analysis, we isolated novel meningococcal restriction-modification (R-M) systems. Nme BI, which is a homologue of the R-M system Hga I of Pasteurella volantium , was present in meningococci of the ET-5 complex and of lineage III. Nme AI was found in serogroup A, ET-37 complex, and cluster A4 meningococci. Nme DI was harbored by meningococci of the ET-37 complex and of cluster A4, but not by serogroup A meningococci. Two of the R-M systems, Nme BI and Nme DI, were located at homologous positions between the phenylalanyl-tRNA synthetase genes pheS and pheT , which appeared to be a preferential target for the insertion of foreign DNA in meningococci. The distribution of the three R-M systems was tested with 103 meningococcal strains comprising 49 sequence types. The vast majority of the strains had either Nme BI, Nme AI, or both Nme AI and Nme DI. Using cocultivation experiments, we could demonstrate that Nme BI, which was present in ET-5 complex meningococci, was responsible for a partial restriction of DNA transfer from meningococci of the ET-37 complex to meningococci of the ET-5 complex.