HOMOLOGY BETWEEN CRYPTIC PLASMID FROM NEISSERIA-GONORRHOEAE AND GENOMIC DNA FROM NEISSERIA-MENINGITIDIS

The human pathogenic Neisseria species N. gonorrhoeae and N. meningiti dis are closely related. In contrast to N. meningitidis, however, almo st all clinical isolates of N. gonorrhoeae harbour a phenotypically cr yptic plasmid. In some gonococcal strains regions of the cryptic plasm id have been found in the gonococcal genome and it has been suggested that large segments of the cryptic plasmid can be integrated into the gonococcal chromosome of both plasmid-bearing and plasmid-free strains . Here we report homology between parts of the cryptic gonococcal plas mid and genomic DNA from four different N. meningitidis strains from s ystemic disease isolates in which no plasmids have been found with the applied methods. Serogroup B strains, causing many of the cases of me ningococcal disease in Norway, hybridized strongly to the cryptic plas mid probe, in contrast to serogroup A and C strains. Clones hybridizin g to the cryptic plasmid were isolated from a meningococcal genomic la mbda EMBL3 DNA library and characterized by restriction mapping. When using one such clone as a probe the parts of the cryptic plasmid showi ng homology to the genomic meningococcal DNA were confined to two smal l separate regions of 420 and 88 bp.