VIBRIO-CHOLERAE O139 BENGAL - COMBINED PHYSICAL AND GENETIC-MAP AND COMPARATIVE-ANALYSIS WITH THE GENOME OF VIBRIO-CHOLERAE O1

A combined physical and genetic map of the genome of strain SG24 of Vi brio cholerae O139 Bengal, a novel non-Ol strain having epidemic poten tial, has been constructed by using the enzymes NotI, SfiI, and CeuI. The genome of SG24 is circular, and the genome size is about 3.57 Mb. The linkages between 47 NotI and 32 SfiI fragments of V. cholerae SG24 genomic DNA were determined by combining two approaches: (i) identifi cation of fragments produced by enzyme I in fragments produced by enzy me II by the method of fragment excision, redigestion, and end labelin g and (ii) use of the linking clone libraries generated from the genom e of classical O1 strain 569B. The linkages between nine CeuI fragment s were determined primarily by analyses of partial fragments of the Ce uI-digested genome. More than 80 cloned homologous and heterologous ge nes, including several operons, have been positioned on the physical m ap. The map of the SG24 genome represents the second map of a V. chole rae genome, and a comparison of this map with that of classical O1 str ain 569B revealed considerable diversity in DNA restriction sites and allowed identification of hypervariable regions. Several genetic marke rs, including virulence determinant genes, are in different positions in the SG24 and 569B genomes.