title: Swarming of Pseudomonas aeruginosa is a complex adaptation leading to increased production of virulence factors and antibiotic resistance.
abstract: In addition to exhibiting swimming and twitching motility, Pseudomonas aeruginosa is able to swarm on semisolid (viscous) surfaces. Recent studies have indicated that swarming is a more complex type of motility influenced by a large number of different genes. To investigate the adaptation process involved in swarming motility, gene expression profiles were analyzed by performing microarrays on bacteria from the leading edge of a swarm zone compared to bacteria growing in identical medium under swimming conditions. Major shifts in gene expression patterns were observed under swarming conditions, including, among others, the overexpression of a large number of virulence-related genes such as those encoding the type III secretion system and its effectors, those encoding extracellular proteases, and those associated with iron transport. In addition, swarming cells exhibited adaptive antibiotic resistance against polymyxin B, gentamicin, and ciprofloxacin compared to what was seen for their planktonic (swimming) counterparts. By analyzing a large subset of up-regulated genes, we were able to show that two virulence genes, lasB and pvdQ, were required for swarming motility. These results clearly favored the conclusion that swarming of P. aeruginosa is a complex adaptation process in response to a viscous environment resulting in a substantial change in virulence gene expression and antibiotic resistance.
authors.affiliation: Centre for Microbial Diseases & Immunity Research, University of British Columbia, 2259 Lower Mall, Vancouver, BC, Canada. joerg@cmdr.ubc.ca
authors.forename: Joerg
authors.initials: J
authors.lastname: Overhage
authors.forename: Manjeet
authors.initials: M
authors.lastname: Bains
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Brazas
authors.forename: Robert E W
authors.initials: RE
authors.lastname: Hancock
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development; D001692:Biological Transport; D002939:Ciprofloxacin / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005839:Gentamicins / Q000494:pharmacology; D008666:Metalloendopeptidases / Q000235:genetics / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D009068:Movement; D020411:Oligonucleotide Array Sequence Analysis; D011112:Polymyxin B / Q000494:pharmacology; D011550:Pseudomonas aeruginosa / Q000502:physiology*; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D005839:Gentamicins; D037521:Virulence Factors; D002939:Ciprofloxacin; D008666:Metalloendopeptidases; C043859:pseudolysin, Pseudomonas aeruginosa; D011112:Polymyxin B