Abstract
Purpose:
To compare the proteomic profile of a clinical isolate of Pseudomonas aeruginosa (P. aeruginosa) obtained from an infected cornea of a contact lens wearer (corneal strain) and a non-corneal strain, ATCC 10145.
Methods:
Phenotypic assays of P. aeruginosa such as twitching motility, biofilm formation and antibiotic sensitivity tests were performed using standard methods. Whole protein lysates were analyzed by Liquid Chromatography/ Tandem Mass Spectrometry (LC-MS/MS) in triplicate and relative protein abundances were determined by spectral counting. G test followed by post hoc Holm Sidak was used for statistical analyses to determine significance in the differential expression of proteins between the two strains.
Results:
LC-MS/MS revealed significant differences in protein composition between the two strains. A total of 585 proteins were detected. Among these 73 were up or down regulated in the corneal strain compared to ATCC10145 and 44 were detected only in the corneal strain. Proteins that were detected explicitly in the corneal strain were involved in different functional groups including cell motility and secretion, lipid metabolism, cell envelope biogenesis and ion transport and metabolism.In addition to a number of hypothetical proteins which had similarities to proteins involved in iron storage, type IV secretion associated lipoproteins, proteases and secreted cytotoxins. Proteins that were significantly upregulated in the corneal strain compared to the non-corneal strain included those involved in motility (flagellin type B, 21fold, p=0.0003), polyhydroxyalkanoate synthesis (PhaF, 11fold, p=0.02), chorismate biosynthesis (chorismate synthase, 8fold, p=0.007) and virulence (lipotoxin F, 3fold, p=0.004). The non ribosomal peptide synthetases (NRPS) were the fourth most abundant proteins in the corneal strain and were missing in ATCC 10145.
Conclusions:
Results from this study confirm that the keratitis associated P. aeruginosa strain is pathogenic and expresses a unique protein profile indicative of phenotypic adaptations to its environment. Identification of the protein profile of the corneal strain of P. aeruginosa in this study will aid in the elucidation of novel intervention strategies to reduce the burden of P. aeruginosa infection in keratitis.
Keywords: 573 keratitis •
664 pseudomonas •
663 proteomics