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Infection and Immunity, July 2006, p. 4190-4199, Vol. 74, No. 7
0019-9567/06/$08.00+0     doi:10.1128/IAI.00926-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Active Genetic Elements Present in the Locus of Enterocyte Effacement in Escherichia coli O26 and Their Role in Mobility

Maite Muniesa,1,{dagger} Mark A. Schembri,2* Nadja Hauf,1 and Trinad Chakraborty1

Institute for Medical Microbiology, Justus-Liebig-University, D-35392 Giessen, Germany,1 School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland 4072, Australia2

Received 17 June 2005/ Returned for modification 30 January 2006/ Accepted 28 March 2006

The locus of enterocyte effacement (LEE) is a large multigene chromosomal segment encoding gene products responsible for the generation of attaching and effacing lesions in many diarrheagenic Escherichia coli strains. A recently sequenced LEE harboring a pathogenicity island (PAI) from a Shiga toxin E. coli serotype O26 strain revealed a LEE PAI (designated LEE O26) almost identical to that obtained from a rabbit-specific enteropathogenic O15:H– strain. LEE O26 comprises 59,540 bp and is inserted at 94 min within the mature pheU tRNA locus. The LEE O26 PAI is flanked by two direct repeats of 137 and 136 bp (DR1 and DR2), as well as a gene encoding an integrase belonging to the P4 integrase family. We examined LEE O26 for horizontal gene transfer. By generating mini-LEE plasmids harboring only DR1 or DR2 with or without the integrase-like gene, we devised a simple assay to examine recombination processes between these sequences. Recombination was shown to be integrase dependent in a {Delta}recA E. coli K-12 strain background. Recombinant plasmids harboring a single direct repeat cloned either with or without the LEE O26 integrase gene were found to insert within the chromosomal pheU locus of E. coli K-12 strains with equal efficiency, suggesting that an endogenous P4-like integrase can substitute for this activity. An integrase with strong homology to the LEE O26 integrase was detected on the K-12 chromosome associated with the leuX tRNA locus at 97 min. Strains deleted for this integrase demonstrated a reduction in the insertion frequency of plasmids harboring only the DR into the pheU locus. These results provide strong evidence that LEE-harboring elements are indeed mobile and suggest that closely related integrases present on the chromosome of E. coli strains contribute to the dynamics of PAI mobility.

* Corresponding author. Mailing address: School of Molecular and Microbial Sciences, University of Queensland, Brisbane, QLD 4072, Australia. Phone: 61 7 3365 3306. Fax: 61 7 3365 4699. E-mail: m.schembri{at}uq.edu.au.

Editor: V. J. DiRita

{dagger} Present address: Department of Microbiology, University of Barcelona, Diagonal 645, 08028 Barcelona, Spain.

Infection and Immunity, July 2006, p. 4190-4199, Vol. 74, No. 7
0019-9567/06/$08.00+0     doi:10.1128/IAI.00926-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Muller, D., Benz, I., Liebchen, A., Gallitz, I., Karch, H., Schmidt, M. A. (2009). Comparative Analysis of the Locus of Enterocyte Effacement and Its Flanking Regions. Infect. Immun. 77: 3501-3513 [Abstract] [Full Text]  
  • van Aartsen, J. J. (2008). The Klebsiella pheV tRNA locus: a hotspot for integration of alien genomic islands. Bioscience Horizons 1: 51-60 [Abstract] [Full Text]  


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