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The Pseudomonas aeruginosa PsrA responds to long-chain fatty acid signals to regulate the fadBA5 β-oxidation operon

Yun Kang

David T. Nguyen

Department of Microbiology, College of Natural Sciences, University of Hawaii at Manoa, Honolulu, HI 96822, USA

Correspondence
Tung T. Hoang
tongh{at}hawaii.edu

β-Oxidative enzymes for fatty acid degradation (Fad) of long-chain fatty acids (LCFAs) are induced in vivo during lung infection in cystic fibrosis patients, and this may contribute to nutrient acquisition and pathogenesis of Pseudomonas aeruginosa. The promoter region of one P. aeruginosa β-oxidation operon, fadBA5 (PA3014 and PA3013), was mapped. Focusing on the transposon mutagenesis of strain PAO1 carrying the P_fadBA5–lacZ fusion, a regulator for the fadBA5 operon was identified to be PsrA (PA3006). Transcriptome analysis of the psrA mutant indicated its importance in regulating β-oxidative enzymes. These microarray data were confirmed by real-time RT-PCR analyses of the fadB5 and lipA (encoding a lipase) genes. Induction of the fadBA5 operon was demonstrated to respond to novel LCFA signals, and this induction required the presence of PsrA, suggesting that LCFAs bind to PsrA to derepress fadBA5. Electrophoretic mobility shift assays indicate specific binding of PsrA to the fadBA5 promoter region. This binding is disrupted by specific LCFAs (C_{18 : 1}⁹, C_{16 : 0}, C_{14 : 0} and, to a lesser extent, C_{12 : 0}), but not by other medium- or short-chain fatty acids or the first intermediate of β-oxidation, acyl-CoA. It is shown here that PsrA is a fadBA5 regulator that binds and responds to LCFA signals in P. aeruginosa.

These authors contributed equally to this work.

A supplementary table listing sequenced chromosomal transposition sites in strain PAO1-P_fadBA5–lacZ and a supplementary figure showing the confirmation of three regulatory mutants affecting the expression of fadBA5 are available with the online version of this paper.

The array data discussed in this paper have been deposited in the NCBI Gene Expression Omnibus (GEO; http://www.ncbi.nlm.nih.gov/geo/) and are accessible through GEO series accession number GSE8083.