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International Journal of Genomics
Volume 2017 (2017), Article ID 8724304, 14 pages
Research Article

Exception to the Rule: Genomic Characterization of Naturally Occurring Unusual Vibrio cholerae Strains with a Single Chromosome

1Los Alamos National Laboratory, Biosciences Division, Genome Science, Los Alamos, NM 87545, USA
2School of Computer, Mathematical and Natural Sciences, Morgan State University, Baltimore, MD 21251, USA
3LOEWE Centre for Synthetic Microbiology-SYNMIKRO, Philipps-Universität Marburg, Hans-Meerwein-Str. 6, 35032 Marburg, Germany
4Tauri Group, LLC, Alexandria, VA 22310, USA
5Defense Biological Product Assurance Office, 110 Thomas Johnson Drive, Frederick, MD 21702, USA

Correspondence should be addressed to Shanmuga Sozhamannan

Received 21 February 2017; Revised 15 June 2017; Accepted 22 June 2017; Published 29 August 2017

Academic Editor: Graziano Pesole

Copyright © 2017 Gary Xie et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The genetic make-up of most bacteria is encoded in a single chromosome while about 10% have more than one chromosome. Among these, Vibrio cholerae, with two chromosomes, has served as a model system to study various aspects of chromosome maintenance, mainly replication, and faithful partitioning of multipartite genomes. Here, we describe the genomic characterization of strains that are an exception to the two chromosome rules: naturally occurring single-chromosome V. cholerae. Whole genome sequence analyses of NSCV1 and NSCV2 (natural single-chromosome vibrio) revealed that the Chr1 and Chr2 fusion junctions contain prophages, IS elements, and direct repeats, in addition to large-scale chromosomal rearrangements such as inversions, insertions, and long tandem repeats elsewhere in the chromosome compared to prototypical two chromosome V. cholerae genomes. Many of the known cholera virulence factors are absent. The two origins of replication and associated genes are generally intact with synonymous mutations in some genes, as are recA and mismatch repair (MMR) genes dam, mutH, and mutL; MutS function is probably impaired in NSCV2. These strains are ideal tools for studying mechanistic aspects of maintenance of chromosomes with multiple origins and other rearrangements and the biological, functional, and evolutionary significance of multipartite genome architecture in general.