The Vibrio cholerae genome contains two unique circular chromosomes

The Vibrio cholerae genome contains two unique circular chromosomes

^*Center for Vaccine Development, Division of Geographic Medicine, Department of Medicine and ^§Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, MD 21201; and ^† Medical Service, Veterans’ Affairs Medical Center, Baltimore, MD 21201

Edited by Stanley Falkow, Stanford University, Stanford, CA, and approved September 11, 1998 (received for review June 15, 1998)

Abstract

Vibrio cholerae, the etiologic agent of the diarrheal disease cholera, is a Gram-negative bacterium that belongs to the γ subdivision of the family Proteobacteriaceae. The physical map of the genome has been reported, and the genome has been described as a single 3.2-Mb chromosome [Majumder, R., et al. (1996) J. Bacteriol. 178, 1105–1112]. By using pulsed-field gel electrophoresis of genomic DNA immobilized in agarose plugs and digested with the restriction enzymes I-CeuI, SfiI, and NotI, we have also constructed the physical map of V. cholerae. Our analysis estimates the size of the genome at 4.0 Mb, 25% larger than the physical map reported by others. Our most notable finding is, however, that the V. cholerae chromosome appears to be not the single chromosome reported but two unique and separate circular megareplicons.

Footnotes

↵ ‡ To whom reprint requests should be addressed at: Center for Vaccine Development, University of Maryland School of Medicine, 685 West Baltimore Street, Baltimore, MD 21201. e-mail: mtrucksi{at}umppa1.ab.umd.edu.
This paper was submitted directly (Track II) to the Proceedings Office.
ABBREVIATION:

PFGE,

pulsed-field gel electrophoresis