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J. Bacteriol. doi:10.1128/JB.00129-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Pseudomonas aeruginosa Twitching Motility Mediated Chemotaxis Towards Phospholipids and Fatty Acids: Specificity and Metabolic Requirements

Department of Microbiology University of Colorado Denver, Aurora, CO 80045; and Department of Medicine National Jewish Medical and Research Center, Denver, CO 80206

^* To whom correspondence should be addressed. Email: mike.vasil{at}uchsc.edu.

	Abstract

Pseudomonas aeruginosa demonstrates type IV pili-mediated directional twitching motility up a gradient of phosphatidylethanolamine (PE). Only one of four extracellular phospholipases C of P. aeruginosa (i.e. PlcB), while not required for twitching motility per se, is required for twitching-mediated migration up a gradient of PE or PC. Whether other lipid metabolism genes are associated with this behavior was assessed by analysis of transcription during twitching up a PE gradient in comparison to transcription during twitching in the absence of any externally applied phospholipid. Data support the hypothesis that PE is further degraded and that the long chain fatty acid (LCFA) moieties of PE are completely metabolized via -oxidation and the glyoxylate shunt. It was discovered that P. aeruginosa exhibits twitching-mediated chemotaxis toward unsaturated LCFAs (e.g. oleic acid), but not saturated LCFAs (e.g. stearic acid) of corresponding lengths. Analysis of mutants that are deficient in glyoxylate shunt enzymes, specifically isocitrate lyase (AceA) and malate synthase (AceB), suggested that the complete metabolism of LCFAs through this pathway was required for the migration of P. aeruginosa up a gradient of PE or unsaturated LCFAs. At this point our data suggested that this process should be classified as energy taxis. However, further evaluation of the ability of AceA and AceB mutants to migrate up a gradient of PE or unsaturated LCFAs in the presence of an alternative energy source clearly indicated that metabolism of LCFAs for energy is not required for chemotaxis toward these compounds.