Genetic diversity of toxigenic and nontoxigenic Vibrio cholerae serogroups O1 and O139 revealed by array-based comparative genomic hybridization.
Toxigenic serogroups O1 and O139 of Vibrio cholerae may cause cholera epidemics or pandemics. Nontoxigenic strains within these serogroups also exist in the environment, and also some may cause sporadic cases of disease. Herein, we investigate the genomic diversity among toxigenic and nontoxigenic O1 and O139 strains by comparative genomic microarray hybridization with the genome of El Tor strain N16961 as a base. Conservation of the toxigenic O1 El Tor and O139 strains is found as previously reported, whereas accumulation of genome changes was documented in toxigenic El Tor strains isolated within the 40 years of the seventh pandemic. High phylogenetic diversity in nontoxigenic O1 and O139 strains is observed, and most of the genes absent from nontoxigenic strains are clustered together in the N16961 genome. By comparing these toxigenic and nontoxigenic strains, we observed that the small chromosome of V. cholerae is quite conservative and stable, outside of the superintegron region. In contrast to the general stability of the genome, the superintegron demonstrates pronounced divergence among toxigenic and nontoxigenic strains. Additionally, sequence variation in virulence-related genes is found in nontoxigenic El Tor strains, and we speculate that these intermediate strains may have pathogenic potential should they acquire CTX prophage alleles and other gene clusters. This genome-wide comparison of toxigenic and nontoxigenic V. cholerae strains may promote understanding of clonal differentiation of V. cholerae and contribute to an understanding of the origins and clonal selection of epidemic strains.
Pang
Bo
B
State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, P.O. Box 5, Changping, Beijing 102206, People's Republic of China.
Yan
Meiying
M
Cui
Zhigang
Z
Ye
Xiaofen
X
Diao
Baowei
B
Ren
Yonghong
Y
Gao
Shouyi
S
Zhang
Liang
L
Kan
Biao
B
D002876:Chromosomes, Bacterial / Q000235:genetics; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D014644:Genetic Variation; D016680:Genome, Bacterial; D008957:Models, Genetic; D009693:Nucleic Acid Hybridization; D020411:Oligonucleotide Array Sequence Analysis; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D041241:Vibrio cholerae O1 / Q000145:classification / Q000235:genetics*; D041242:Vibrio cholerae O139 / Q000145:classification / Q000235:genetics*