A NheI macrorestriction map of the Neisseria meningitidis B1940 genome.

A macrorestriction map of the Neisseria meningitidis strain B1940 genome was constructed by two-dimensional pulsed-field gel electrophoresis (2D-PFGE) techniques. Digestion of the genomic DNA with the restriction endonuclease NheI revealed 15 fragments between 10 kb and 450 kb. The sum of the fragments and resolution of the linearized chromosome yielded a total genome size of about 2.3 Mbp. By overlapping methylation with the AluI-methylase six NheI recognition sites could be blocked. Fragments were ordered by partial/complete 2D-PFGE of genomic DNA with and without prior AluI methylation, respectively. All nine AluI-methylase/NheI and 14 NheI restriction sites could be mapped on a single circular chromosome. This map will serve as a useful tool for further genetic analysis of meningococci and exemplifies the power of non-radioactive 2D-PFGE techniques to construct large physical genome maps with a single restriction enzyme.