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

• Published in: Applied and Environmental Microbiology Vol. 75; no. 4; pp. 937 - 945
• Main Authors: Méndez, J, Fernández, L, Menéndez, A, Reimundo, P, Pérez-Pascual, D, Navais, R, Guijarro, J.A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for Microbiology 01-02-2009; American Society for Microbiology (ASM)
• Subjects: Animals; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological and medical sciences; Chromosomes; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Fish Diseases - microbiology; Fundamental and applied biological sciences. Psychology; Gene Expression Profiling; Gene Order; Genes; Genetic research; Genetics and Molecular Biology; Genomic analysis; Genomics; Lethal Dose 50; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Microbiology; Molecular Sequence Data; Mutagenesis, Insertional; Mutation; Oncorhynchus mykiss - microbiology; Operon; Pathogens; Protein Transport; Sequence Analysis, DNA; Sequence Homology; Serratia - genetics; Serratia entomophila; Temperature; Virulence; Virulence Factors - genetics; Virulence Factors - metabolism; Yersinia - genetics; Yersinia - pathogenicity; Bacteria; Operon; Secretion; Yersinia ruckeri; Virulence; Enterobacteriaceae
• ISSN: 0099-2240; 1098-5336; 1098-6596
• DOI: 10.1128/AEM.01377-08

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: