Dataset Information

Acquisition and evolution of the exoU locus in Pseudomonas aeruginosa.

ABSTRACT: ExoU is a potent Pseudomonas aeruginosa cytotoxin translocated into host cells by the type III secretion system. A comparison of genomes of various P. aeruginosa strains showed that that the ExoU determinant is found in the same polymorphic region of the chromosome near a tRNA(Lys) gene, suggesting that exoU is a horizontally acquired virulence determinant. We used yeast recombinational cloning to characterize four distinct ExoU-encoding DNA segments. We then sequenced and annotated three of these four genomic regions. The sequence of the largest DNA segment, named ExoU island A, revealed many plasmid- and genomic island-associated genes, most of which have been conserved across a broad set of beta- and gamma-Proteobacteria. Comparison of the sequenced ExoU-encoding genomic islands to the corresponding PAO1 tRNA(Lys)-linked genomic island, the pathogenicity islands of strain PA14, and pKLC102 of clone C strains allowed us to propose a mechanism for the origin and transmission of the ExoU determinant. The evolutionary history very likely involved transposition of the ExoU determinant onto a transmissible plasmid, followed by transfer of the plasmid into different P. aeruginosa strains. The plasmid subsequently integrated into a tRNA(Lys) gene in the chromosome of each recipient, where it acquired insertion sequences and underwent deletions and rearrangements. We have also applied yeast recombinational cloning to facilitate a targeted mutagenesis of ExoU island A, further demonstrating the utility of the specific features of the yeast capture vector for functional analyses of genes on large horizontally acquired genetic elements.

SUBMITTER: Kulasekara BR

PROVIDER: S-EPMC1482899 | biostudies-literature | 2006 Jun

REPOSITORIES: biostudies-literature

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Acquisition and evolution of the exoU locus in Pseudomonas aeruginosa.

Kulasekara Bridget R BR Kulasekara Hemantha D HD Wolfgang Matthew C MC Stevens Lisa L Frank Dara W DW Lory Stephen S

Journal of bacteriology 20060601 11

ExoU is a potent Pseudomonas aeruginosa cytotoxin translocated into host cells by the type III secretion system. A comparison of genomes of various P. aeruginosa strains showed that that the ExoU determinant is found in the same polymorphic region of the chromosome near a tRNA(Lys) gene, suggesting that exoU is a horizontally acquired virulence determinant. We used yeast recombinational cloning to characterize four distinct ExoU-encoding DNA segments. We then sequenced and annotated three of the ...[more]

PMID: 16707695

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Project description:UNLABELLED:The Pseudomonas aeruginosa type III secretion system has been associated with poor outcomes in both animal models and human patients. Despite a large number of studies exploring the regulation of type III secretion in vitro, little is known about the timing of secretion during mammalian infection. Here we demonstrate that the exoU gene, which encodes the highly cytotoxic type III effector ExoU, is induced early during acute P. aeruginosa pneumonia. Immunofluorescence microscopy indicated that the amount of ExoU protein in the lung also increased over time. The importance of early expression was examined using a strain of P. aeruginosa with inducible production of ExoU. Delays in expression as short as 3 h led to reduced bacterial burdens in the lungs of mice and improved survival. Our results demonstrate that early expression of exoU is critical to bacterial survival during pneumonia and suggest that therapeutic interventions that delay ExoU secretion for even short periods of time may be efficacious. IMPORTANCE:Pseudomonas aeruginosa is a major contributor to the large numbers of health care-associated infections occurring annually, particularly for immunocompromised patients. Although this organism possesses many virulence factors, the type III secretion system plays an especially important role in both animal models and humans. This system forms a needle-like apparatus that injects toxins directly into eukaryotic cells. The most toxic protein secreted by this molecular machine is ExoU, which causes rapid cell death. In this study, we demonstrated that exoU was expressed and ExoU was produced early during acute pneumonia in a mouse model. Delaying expression of exoU by as little as 3 h enhanced clearance of bacteria and survival of infected mice. Our findings highlight the importance of understanding the regulation of virulence factor expression during infection when designing therapeutic strategies to inhibit the toxic effects of these proteins.

Dataset Information

Acquisition and evolution of the exoU locus in Pseudomonas aeruginosa.

Publications

Acquisition and evolution of the exoU locus in Pseudomonas aeruginosa.

Similar Datasets

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