Molecular characterisation of the vacuolating autotransporter toxin in Uropathogenic Escherichia coli

Nichols, Katie B., Totsika, Makrina, Moriel, Danilo G., Lo, Alvin W., Yang, Ji, Wurpel, Daniël J., Rossiter, Amanda E., Strugnell, Richard A., Henderson, Ian R., Ulett, Glen C., Beatson, Scott A., & Schembri, Mark A. (2016) Molecular characterisation of the vacuolating autotransporter toxin in Uropathogenic Escherichia coli. Journal of Bacteriology, 198(10), pp. 1487-1498.

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Abstract

The vacuolating autotransporter (AT) toxin (Vat) contributes to Uropathogenic Escherichia coli (UPEC) fitness during systemic infection. Here we characterised Vat and investigated its regulation in UPEC. We assessed the prevalence of vat in a collection of 45 UPEC urosepsis strains and showed that it was present in 31 (68%) of the isolates. The isolates containing the vat gene corresponded to three major E. coli sequence types (ST12, 73 and 95) and these strains secreted the Vat protein. Further analysis of the vat genomic locus identified a conserved gene located directly downstream of vat that encodes a putative MarR-like transcriptional regulator, which we termed vatX. The vat-vatX genes were present in the UPEC reference strain CFT073 and RT-PCR revealed both genes are co-transcribed. Over-expression of vatX in CFT073 led to a 3-fold increase in vat gene transcription. The vat promoter region contained three putative nucleation sites for the global transcriptional regulator H-NS; thus the hns gene was mutated in CFT073 (to generate CFT073hns). Western blot analysis using a Vat-specific antibody revealed a significant increase in Vat expression in CFT073hns compared to wild-type CFT073. Direct H-NS binding to the vat promoter region was demonstrated using purified H-NS in combination with electrophoresis mobility shift assays. Finally, Vat-specific antibodies were detected in plasma samples from urosepsis patients infected by vat-containing UPEC strains, demonstrating Vat is expressed during infection. Overall, this study has demonstrated that Vat is a highly prevalent and tightly regulated immunogenic SPATE secreted by UPEC during infection.

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ID Code: 93571
Item Type: Journal Article
Refereed: Yes
DOI: 10.1128/JB.00791-15
ISSN: 1098-5530
Divisions: Current > Schools > School of Biomedical Sciences
Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: 2016 American Society for Microbiology
Deposited On: 08 Mar 2016 05:18
Last Modified: 21 Jun 2016 16:39

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