Open AccessMultiple independent origins of Shigella clones ofEscherichia coliand convergent evolution of many of their characteristics
Author(s) -
Gulietta M. Pupo,
Ruiting Lan,
Peter R. Reeves
Publication year - 2000
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.180094797
Subject(s) - shigella boydii , shigella , biology , shigellosis , shigella dysenteriae , shigella flexneri , shigella sonnei , microbiology and biotechnology , escherichia coli , genetics , serotype , dysentery , gene
The evolutionary relationships of 46 Shigella strains representing each of the serotypes belonging to the four traditional Shigella species (subgroups), Dysenteriae, Flexneri, Boydii, and Sonnei, were determined by sequencing of eight housekeeping genes in four regions of the chromosome. Analysis revealed a very similar evolutionary pattern for each region. Three clusters of strains were identified, each including strains from different subgroups. Cluster 1 contains the majority of Boydii and Dysenteriae strains (B1–4, B6, B8, B10, B14, and B18; and D3–7, D9, and D11–13) plus Flexneri 6 and 6A. Cluster 2 contains seven Boydii strains (B5, B7, B9, B11, B15, B16, and B17) and Dysenteriae 2. Cluster 3 contains one Boydii strain (B12) and the Flexneri serotypes 1–5 strains. Sonnei and three Dysenteriae strains (D1, D8, and D10) are outside of the three main clusters but, nonetheless, are clearly withinEscherichia coli . Boydii 13 was found to be distantly related toE. coli . Shigella strains, like the other pathogenic forms ofE. coli , do not have a single evolutionary origin, indicating convergent evolution of Shigella phenotypic properties. We estimate the three main Shigella clusters to have evolved within the last 35,000 to 270,000 years, suggesting that shigellosis was one of the early infectious diseases of humans.