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Applied and Environmental Microbiology, February 2009, p. 937-945, Vol. 75, No. 4
0099-2240/09/$08.00+0     doi:10.1128/AEM.01377-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

A Chromosomally Located traHIJKCLMN Operon Encoding a Putative Type IV Secretion System Is Involved in the Virulence of Yersinia ruckeri{triangledown}

J. Méndez, L. Fernández, A. Menéndez, P. Reimundo, D. Pérez-Pascual, R. Navais, and J. A. Guijarro*

Área de Microbiología, Departamento de Biología Funcional, Facultad de Medicina, IUBA, Universidad de Oviedo, 33006 Oviedo, Spain

Received 19 June 2008/ Accepted 8 December 2008

Nucleotide sequence analysis of the region surrounding the pIVET8 insertion site in Yersinia ruckeri 150RiviXII, previously selected by in vivo expression technology (IVET), revealed the presence of eight genes (traHIJKCLMN [hereafter referred to collectively as the tra operon or tra cluster]), which are similar both in sequence and organization to the tra operon cluster found in the virulence-related plasmid pADAP from Serratia entomophila. Interestingly, the tra cluster of Y. ruckeri is chromosomally encoded, and no similar tra cluster has been identified yet in the genomic analysis of human pathogenic yersiniae. A traI insertional mutant was obtained by homologous recombination. Coinfection experiments with the mutant and the parental strain, as well as 50% lethal dose determinations, indicate that this operon is involved in the virulence of this bacterium. All of these results suggest the implication of the tra cluster in a virulence-related type IV secretion/transfer system. Reverse transcriptase PCR studies showed that this cluster is transcribed as an operon from a putative promoter located upstream of traH and that the mutation of traI had a polar effect. A traI::lacZY transcriptional fusion displayed higher expression levels at 18°C, the temperature of occurrence of the disease, and under nutrient-limiting conditions. PCR detection analysis indicated that the tra cluster is present in 15 Y. ruckeri strains from different origins and with different plasmid profiles. The results obtained in the present study support the conclusion, already suggested by different authors, that Y. ruckeri is a very homogeneous species that is quite different from the other members of the genus Yersinia.

* Corresponding author. Mailing address: Área de Microbiología, Facultad de Medicina, Universidad de Oviedo, 33006 Oviedo, Asturias, Spain. Phone: 34985104218. Fax: 34985103148. E-mail: jaga{at}fq.uniovi.es

{triangledown} Published ahead of print on 16 December 2008.

Applied and Environmental Microbiology, February 2009, p. 937-945, Vol. 75, No. 4
0099-2240/09/$08.00+0     doi:10.1128/AEM.01377-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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