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Published on: May 4, 2018
Characterization of protease IV expression in Pseudomonas aeruginosa clinical isolates
Tim C R Conibear1,2, Mark D P Willcox3,1,2, Judith L Flanagan3
1The Vision Co-operative Research Centre, Sydney, Australia.
Abstract:
Expression of protease IV by Pseudomonas aeruginosa during ocular infections contributes significantly to tissue damage. However, several P. aeruginosa strains isolated from ocular infections or inflammatory events produce very low levels of protease IV. The aim of the present study was to characterize, genetically and phenotypically, the presence and expression of the protease IV gene in a group of clinical isolates that cause adverse ocular events of varying degrees, and to elucidate the possible control mechanisms of expression associated with this virulence factor. Protease IV gene sequences from seven clinical isolates of P. aeruginosa were determined and compared to P. aeruginosa strains PAO1 and PA103-29. Production and enzyme activity of protease IV were measured in test strains and compared to that of quorum-sensing gene (lasRI) mutants and the expression of other virulence factors. Protease IV gene sequence similarities between the isolates were 97.5-99.5 %. The strains were classified into two distinct phylogenetic groups that correlated with the presence of exo-enzymes from type three secretion systems (TTSS). Protease IV concentrations produced by PAOΔlasRI mutants and the two clinical isolates with a lasRI gene deficiency were restored to levels comparable to strain PAO1 following complementation of the quorum-sensing gene deficiencies. The protease IV gene is highly conserved in P. aeruginosa clinical isolates that cause a range of adverse ocular events. Observed variations within the gene sequence appear to correlate with presence of specific TTSS genes. Protease IV expression was shown to be regulated by the Las quorum-sensing system.
Insights
Pseudomonas aeruginosa protease IV gene is highly conserved in clinical isolates causing eye infections. Its expression is regulated by the Las quorum-sensing system, impacting virulence.
Area of Science:
- Microbiology
- Ocular infections
- Bacterial pathogenesis
Background:
- Protease IV from Pseudomonas aeruginosa is a key factor in ocular tissue damage.
- Some P. aeruginosa strains from eye infections exhibit low protease IV production.
- Understanding protease IV regulation is crucial for managing ocular infections.
Purpose of the Study:
- To genetically and phenotypically characterize protease IV gene presence and expression in clinical P. aeruginosa isolates.
- To investigate the control mechanisms of protease IV expression in ocular infections.
- To correlate genetic variations with virulence factor expression.
Main Methods:
- Sequencing of the protease IV gene in seven clinical isolates and comparison with reference strains.
- Measurement of protease IV production and enzyme activity.
- Analysis of quorum-sensing gene (lasRI) mutants and complementation studies.
- Phylogenetic analysis and correlation with type three secretion system (TTSS) genes.
Main Results:
- Protease IV gene sequences showed high similarity (97.5-99.5%) across isolates.
- Clinical isolates grouped into two distinct phylogenetic clusters linked to TTSS gene presence.
- Restoration of protease IV production in lasRI-deficient strains via gene complementation.
- Protease IV expression is significantly influenced by the Las quorum-sensing system.
Conclusions:
- The protease IV gene is highly conserved in P. aeruginosa causing ocular events.
- Gene sequence variations correlate with specific TTSS gene profiles.
- The Las quorum-sensing system is a primary regulator of protease IV expression in P. aeruginosa.
