This Article Figures Only Full Text Full Text (PDF) Supporting Information Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a colleague Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Copyright Permission Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Faruque, S. M. Articles by Nair, G. B. Search for Related Content PubMed PubMed Citation Articles by Faruque, S. M. Articles by Nair, G. B. Social Bookmarking                What's this?

 Previous Article  | Table of Contents |  Next Article 

BIOLOGICAL SCIENCES / MICROBIOLOGY
Genomic analysis of the Mozambique strain of Vibrio cholerae O1 reveals the origin of El Tor strains carrying classical CTX prophage

Shah M. Faruque^*,, Vincent C. Tam, Nityananda Chowdhury^*, Pornphan Diraphat, Michelle Dziejman^,¶, John F. Heidelberg^||, John D. Clemens^**, John J. Mekalanos, and G. Balakrish Nair^*,

*Molecular Genetics Laboratory, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka-1212, Bangladesh; Department of Microbiology, Faculty of Public Health, Mahidol University, Bangkok 73170, Thailand; ^¶School of Medicine and Dentistry, University of Rochester, 601 Elmwood Avenue, Box 672, Rochester, NY 14642; ^||The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850; **International Vaccine Institute, Kwanak, P.O. Box 14, Seoul 151-600, Korea; and Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115

Contributed by G. Balakrish Nair, January 17, 2007 (received for review January 5, 2007)

Cholera outbreaks in subSaharan African countries are caused by strains of the El Tor biotype of toxigenic Vibrio cholerae O1. The El Tor biotype is the causative agent of the current seventh cholera pandemic, whereas the classical biotype, which was associated with the sixth pandemic, is now extinct. Besides other genetic differences the CTX prophages encoding cholera toxin in the two biotypes of V. cholerae O1 have distinct repressor (rstR) genes. However, recent incidences of cholera in Mozambique were caused by an El Tor biotype V. cholerae O1 strain that, unusually, carries a classical type (CTX^class) prophage. We conducted genomic analysis of the Mozambique strain and its CTX prophage together with chromosomal phage integration sites to understand the origin of this atypical strain and its evolutionary relationship with the true seventh pandemic strain. These analyses showed that the Mozambique strain carries two copies of CTX^class prophage located on the small chromosome in a tandem array that allows excision of the prophage, but the excised phage genome was deficient in replication and did not produce CTX^class virion. Comparative genomic microarray analysis revealed that the strain shares most of its genes with the typical El Tor strain N16961 but did not carry the TLC gene cluster, and RS1 sequence, adjacent to the CTX prophage. Our data are consistent with the Mozambique strain's having evolved from a progenitor similar to the seventh pandemic strain, involving multiple recombination events and suggest a model for origination of El Tor strains carrying the classical CTX prophage.

cholera | CTX phage | TLC element | evolution

The authors declare no conflict of interest.

This article contains supporting information online at www.pnas.org/cgi/content/full/0700365104/DC1.

To whom correspondence may be addressed. E-mail: faruque{at}icddrb.org or gbnair{at}icddrb.org

© 2007 by The National Academy of Sciences of the USA

CiteULike    Complore    Connotea    Del.icio.us    Digg    What's this?

Current Issue | Archives | Online Submission | Info for Authors | Editorial Board | About Subscribe | Advertise | Contact | Site Map Copyright © 2007 by the National Academy of Sciences