title: Characterization of protease IV expression in Pseudomonas aeruginosa clinical isolates.
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.
authors.affiliation: The Vision Co-operative Research Centre, Sydney, Australia.|School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Tim C R
authors.initials: TCR
authors.lastname: Conibear
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.|The Vision Co-operative Research Centre, Sydney, Australia.|School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Mark D P
authors.initials: MDP
authors.lastname: Willcox
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.
authors.forename: Judith L
authors.initials: JL
authors.lastname: Flanagan
authors.affiliation: Brien Holden Vision Institute, Sydney, Australia.|The Vision Co-operative Research Centre, Sydney, Australia.|School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhu
mesh_terms: D017124:Conserved Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000096:biosynthesis* / Q000235:genetics; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D053038:Quorum Sensing; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D037521:Virulence Factors / Q000096:biosynthesis / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D037521:Virulence Factors; D010447:Peptide Hydrolases; C030732:protease IV