Proteomic profiling of Pseudomonas aeruginosa AES-1R, PAO1 and PA14 reveals potential virulence determinants associated with a transmissible cystic fibrosis-associated strain

Abstract

Background: Pseudomonas aeruginosa is an opportunistic pathogen that is the major cause of morbidity and mortality in patients with cystic fibrosis (CF). While most CF patients are thought to acquire P. aeruginosa from the environment, person-person transmissible strains have been identified in CF clinics worldwide. The molecular basis for transmissibility and colonization of the CF lung remains poorly understood.

Results: A dual proteomics approach consisting of gel-based and gel-free comparisons were undertaken to analyse protein profiles in a transmissible, early (acute) isolate of the Australian epidemic strain 1 (AES-1R), the virulent burns/wound isolate PA14, and the poorly virulent, laboratory-associated strain PAO1. Over 1700 P. aeruginosa proteins were confidently identified. AES-1R protein profiles revealed elevated abundance of proteins associated with virulence and siderophore biosynthesis and acquisition, antibiotic resistance and lipopolysaccharide and fatty acid biosynthesis. The most abundant protein in AES-1R was confirmed as a previously hypothetical protein with sequence similarity to carbohydrate-binding proteins and database search revealed this gene is only found in the CF-associated strain PA2192. The link with CF infection may suggest that transmissible strains have acquired an ability to rapidly interact with host mucosal glycoproteins.

Conclusions: Our data suggest that AES-1R expresses higher levels of proteins, such as those involved in antibiotic resistance, iron acquisition and virulence that may provide a competitive advantage during early infection in the CF lung. Identification of novel proteins associated with transmissibility and acute infection may aid in deciphering new strategies for intervention to limit P. aeruginosa infections in CF patients.

Figure 1

Two-dimensional gel electrophoresis of proteins from P. aeruginosa AES-1R (A), PAO1 (B), and PA14 (C). Spot numbers refer to protein identifications as shown in Additional file 2. Boxes indicate positions of multiple spots with the same identification.

Figure 2

Predicted protein sequence of a P. aeruginosa AES-1R hypothetical protein ((A); AES_7139; spot 43a-e) characterized by MALDI-MS and LC-MS/MS (B). Peptide Mass, peptides observed by either LC-MS/MS (charge states > +1) or by peptide mapping (charge state +1); Sequence, peptide sequence defined by assignment of y- and b-ions and confirmed by manual interpretation of the MS/MS spectra (920.4535 (+1); matched by mass alone); Note, modifications to sequence identified by MS. Peptides identified by MS are underlined in the protein sequence. Note the non-tryptic N-terminal peptide (958.5200 (+3) m/z), suggesting the methionine at position 7 is the true N-terminus. Cysteine residue potentially involved in disulfide bond/homodimer formation is marked with (*).