title: The olsA gene mediates the synthesis of an ornithine lipid in Pseudomonas aeruginosa during growth under phosphate-limiting conditions, but is not involved in antimicrobial peptide susceptibility.
abstract: Pseudomonas aeruginosa responds to phosphate limitation by inducing the expression of phosphate transport systems, phosphatases, hemolysins and a DNase, many of which are important for virulence. Here we report that under phosphate-limiting conditions, P. aeruginosa produces a phosphate-free ornithine lipid (OL) as the primary membrane lipid. The olsBA (PA4350-PA4351) genes were highly induced under phosphate-limiting conditions. The production and structure of the OL was confirmed by MS, revealing diagnostic fragment ions and mainly C16 : 0 and C18 : 1 dialkyl chains. It was shown that olsA is required for production of these lipids and genetic complementation of the olsA∷lux mutant restored OL production. Studies in other bacteria have correlated increased resistance to antimicrobial peptides with the production of OLs. Here it was demonstrated that resistance to antimicrobial peptides increased under phosphate-limiting conditions, but OLs were not required for this increased resistance. OL production was also not required for virulence in the Caenorhabditis elegans infection model. The production of OLs is a strategy to reduce phosphate utilization in the membrane, but mutants unable to produce OLs have no observable phenotype with respect to growth, antibiotic resistance or virulence.
authors.affiliation: Department of Microbiology and Infectious Diseases, Health Sciences Centre, University of Calgary, AB, Canada. slewenza@ucalgary.ca
authors.forename: Shawn
authors.initials: S
authors.lastname: Lewenza
authors.forename: Reza
authors.initials: R
authors.lastname: Falsafi
authors.forename: Manjeet
authors.initials: M
authors.lastname: Bains
authors.forename: Patricia
authors.initials: P
authors.lastname: Rohs
authors.forename: Jacek
authors.initials: J
authors.lastname: Stupak
authors.forename: G Dennis
authors.initials: GD
authors.lastname: Sprott
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Hancock
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans; D002855:Chromatography, Thin Layer; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008055:Lipids / Q000235:genetics*; D008563:Membrane Lipids / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009952:Ornithine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D010710:Phosphates; D011112:Polymyxin B / Q000494:pharmacology; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D014774:Virulence
chemical_list: D008055:Lipids; D008563:Membrane Lipids; D010710:Phosphates; C051524:ornithine containing aminolipid; D009952:Ornithine; D011112:Polymyxin B