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J. Bacteriol., Feb 1996, 1105-1112, Vol 178, No. 4
R Majumder, S Sengupta, G Khetawat, RK Bhadra, S Roychoudhury and J Das
A combined physical and genetic map of the genome of the classical O1
hypertoxinogenic strain 569B of Vibrio cholerae has been constructed. The
enzymes NotI, SfiI and CeuI generated DNA fragments of suitable size
distribution that could be resolved by pulsed-field gel electrophoresis.
The digests produced 37, 22, and 7 fragments, respectively. The CeuI maps
of the genomes of strains 569B and O395, constructed by partial restriction
digestion, were identical, and the data are consistent with the concept of
circular chromosomes. The genome size of each of the strains was estimated
to be about 3.2 Mb. The NotI and SfiI digestion profiles of the genomic
DNAs of strains 569B and O395 exhibited distinct restriction fragment
length polymorphism. The linkages between the 37 NotI fragments of the
genome of strain 569B were determined by combining three approaches:
isolation of linking clones, analysis of partial digestion fragments, and
identification of NotI fragments in isolated CeuI and SfiI fragments. To
align linked fragments precisely, NotI-digested genomic DNA was end labeled
and separated in the same gel with the NotI-digested DNA to be probed with
linking clones. This also allowed the identification of smaller restriction
fragments that are not visible in ethidium bromide- stained gels. The
presence of repetitive DNA sequences in the V. cholerae 569B genome has
been demonstrated. Twenty cloned homologous and heterologous genes and
seven rrn operons have been positioned on the physical map. The two copies
of the Ctx genetic element in the genome of strain 569B are located about
1,000 kb apart.
Copyright © 1996, American Society for Microbiology
Physical map of the genome of Vibrio cholerae 569B and localization of genetic markers
Biophysics Division, Indian Institute of Chemical Biology, Calcutta, India.
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