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Journal of Bacteriology, June 2004, p. 3547-3560, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3547-3560.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

The ETT2 Gene Cluster, Encoding a Second Type III Secretion System from Escherichia coli, Is Present in the Majority of Strains but Has Undergone Widespread Mutational Attrition

Chuan-Peng Ren,1 Roy R. Chaudhuri,1 Amanda Fivian,1 Christopher M. Bailey,1 Martin Antonio,1 Wayne M. Barnes,2 and Mark J. Pallen1*

Bacterial Pathogenesis and Genomics Unit, Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham B15 2TT, United Kingdom,1 Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri 631102

Received 19 September 2003/ Accepted 12 February 2004

ETT2 is a second cryptic type III secretion system in Escherichia coli which was first discovered through the analysis of genome sequences of enterohemorrhagic E. coli O157:H7. Comparative analyses of Escherichia and Shigella genome sequences revealed that the ETT2 gene cluster is larger than was previously thought, encompassing homologues of genes from the Spi-1, Spi-2, and Spi-3 Salmonella pathogenicity islands. ETT2-associated genes, including regulators and chaperones, were found at the same chromosomal location in the majority of genome-sequenced strains, including the laboratory strain K-12. Using a PCR-based approach, we constructed a complete tiling path through the ETT2 gene cluster for 79 strains, including the well-characterized E. coli reference collection supplemented with additional pathotypes. The ETT2 gene cluster was found to be present in whole or in part in the majority of E. coli strains, whether pathogenic or commensal, with patterns of distribution and deletion mirroring the known phylogenetic structure of the species. In almost all strains, including enterohemorrhagic E. coli O157:H7, ETT2 has been subjected to varying degrees of mutational attrition that render it unable to encode a functioning secretion system. A second type III secretion system-associated locus that likely encodes the ETT2 translocation apparatus was found in some E. coli strains. Intact versions of both ETT2-related clusters are apparently present in enteroaggregative E. coli strain O42.


* Corresponding author. Mailing address: Bacterial Pathogenesis and Genomics Unit, Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham B15 2TT, United Kingdom. Phone: (44) 121 414 7163. Fax: (44) 121 414 3454. E-mail: m.pallen{at}bham.ac.uk.


Journal of Bacteriology, June 2004, p. 3547-3560, Vol. 186, No. 11
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.11.3547-3560.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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