The host-restricted bacterium Streptococcus equi is the causative agent of equine strangles, the most frequently diagnosed infectious disease of horses worldwide. The disease is characterized by abscessation of the lymph nodes of the head and neck, leading to significant welfare and economic cost. S. equi is believed to have evolved from an ancestral strain of Streptococcus zooepidemicus, an opportunistic pathogen of horses and other animals. Comparison of the genome of S. equi strain 4047 with those of S. zooepidemicus identified examples of gene loss due to mutation and deletion, and gene gain through the acquisition of mobile genetic elements that have probably shaped the pathogenic specialization of S. equi. In particular, deletion of the CRISPR (clustered regularly interspaced short palindromic repeats) locus in the ancestor of S. equi may have predisposed the bacterium to acquire and incorporate new genetic material into its genome. These include four prophages and a novel integrative conjugative element. The virulence cargo carried by these mobile genetic elements is believed to have shaped the ability of S. equi to cause strangles. Further sequencing of S. zooepidemicus has highlighted the diversity of this opportunistic pathogen. Again, CRISPRs are postulated to influence evolution, balancing the need for gene gain over genome stability. Analysis of spacer sequences suggest that these pathogens may be susceptible to a limited range of phages and provide further evidence of cross-species exchange of genetic material among Streptococcus pyogenes, Streptococcus agalactiae and Streptococcus dysgalactiae.
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Conference Article|
November 20 2013
Streptococcus zooepidemicus and Streptococcus equi evolution: the role of CRISPRs
Andrew S. Waller;
Andrew S. Waller
1
*Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, U.K.
1To whom correspondence should be addressed (emailandrew.waller@aht.org.uk).
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Carl Robinson
Carl Robinson
*Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, U.K.
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Publisher: Portland Press Ltd
Received:
July 24 2013
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2013 Biochemical Society
2013
Biochem Soc Trans (2013) 41 (6): 1437–1443.
Article history
Received:
July 24 2013
Citation
Andrew S. Waller, Carl Robinson; Streptococcus zooepidemicus and Streptococcus equi evolution: the role of CRISPRs. Biochem Soc Trans 1 December 2013; 41 (6): 1437–1443. doi: https://doi.org/10.1042/BST20130165
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