Secretome of Transmissible <i>Pseudomonas aeruginosa</i> AES-1R Grown in a Cystic Fibrosis Lung-Like Environment

<i>Pseudomonas aeruginosa</i> is the predominant cause of mortality in patients with cystic fibrosis (CF). We examined the secretome of an acute, transmissible CF <i>P. aeruginosa</i> (Australian epidemic strain 1-R; AES-1R) compared with laboratory-adapted PAO1. Culture supernatant proteins from rich (LB) and minimal (M9) media were compared using 2-DE and 2DLC-MS/MS, which revealed elevated abundance of PasP protease and absence of AprA protease in AES-1R. CF lung-like artificial sputum medium (ASMDM) contains serum and mucin that generally preclude proteomics of secreted proteins. ASMDM culture supernatants were subjected to 2DLC-MS/MS, which allowed the identification of 57 <i>P. aeruginosa</i> proteins, and qualitative spectral counting was used to estimate relative abundance. AES-1R-specific AES_7139 and PasP were more abundant in AES-1R ASMDM culture supernatants, while AprA could only be identified in PAO1. Relative quantitation was performed using selected reaction monitoring. Significantly elevated levels of PasP, LasB, chitin-binding protein (CbpD), and PA4495 were identified in AES-1R ASMDM supernatants. Quantitative PCR showed elevated <i>pasP</i> in AES-1R during early (18 h) ASMDM growth, while no evidence of <i>aprA</i> expression could be observed. Genomic screening of CF isolates revealed <i>aes_7139</i> was present in all AES-1 and one pair of sequential nonepidemic isolates. Secreted proteins may be crucial in aiding CF-associated <i>P. aeruginosa</i> to establish infection and for adaptation to the CF lung.