Genetic isolation of meningococci of the electrophoretic type 37 complex

Neisseria. meningitidis (the meningococcus) is a naturally competent bacter ial species in which intra- and interspecific horizontal gene transfer is a major source of genetic diversity. In strains of the electrophoretic type 37 (ET37) complex and of the A14 cluster, we identified genomic DNA coding for a novel restriction-modification system and for the tail of a previousl y unidentified prophage. Furthermore, a novel 7.2-kb DNA segment restricted to clones of the ET-37 complex and the A4 cluster was isolated and shown t o occur both as a plasmid (pJS-B) and as a chromosomal integration. Neither the genomic loci nor pJS-B was present in ET-5 complex, lineage,3, or sero group A meningococci, The differential distribution of the DNA segments des cribed herein, as well as of opcA, porB, nmeAI, nmeBI, and nmeDI described previously, supports the concept of genetic isolation of hypervirulent line ages responsible for most cases of serogroup C disease worldwide.