title: Effects of osmotic stress on rhamnolipid synthesis and time-course production of cell-to-cell signal molecules by Pseudomonas aeruginosa.
abstract: Biosynthesis of biosurfactant rhamnolipids by Pseudomonas aeruginosa depends on two hierarchical quorum sensing systems, LasRI and RhlRI, which synthesize and sense the signal molecules N-(3-oxododecanoyl)-L-homoserine lactone (3OC₁₂-HSL) and N-butyryl-L-homoserine lactone (C₄-HSL), respectively. The Pseudomonas Quinolone Signal (PQS) is a third cell-to-cell signal molecule connecting these two systems, and its precursor, 2-heptyl-4-quinolone (HHQ), also constitutes a signal. The chronology of the production of signal molecules and rhamnolipids was determined during growth in PPGAS medium. Hyperosmotic condition (0.5 M NaCl) moderately affected growth, and led to intra-cellular accumulation of compatible solutes. Production of signal molecules was delayed and their highest concentrations were 2.5 to 5 fold lower than in NaCl-free PPGAS, except for HHQ, the highest concentration of which was increased. The presence of NaCl prevented rhamnolipid synthesis. When the osmoprotectant glycine betaine was added to PPGAS/NaCl medium, it was imported by the cells without being metabolized. This did not improve growth, but reestablished the time-courses of HSL and HHQ accumulation and fully or partially restored the HSL and PQS levels. It also partially restored rhamnolipid production. Quantification of mRNAs encoding enzymes involved in HSL, PQS, and rhamnolipid biosyntheses confirmed the effect of hyperosmotic stress and glycine betaine at the gene expression level.
authors.affiliation: Laboratoire de Biotechnologie et Chimie Marines, EA 3884, Université de Bretagne Sud, UEB, BP 92116, 56321 Lorient, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Bazire
authors.forename: Farès
authors.initials: F
authors.lastname: Diab
authors.forename: Laure
authors.initials: L
authors.lastname: Taupin
authors.forename: Sophie
authors.initials: S
authors.lastname: Rodrigues
authors.forename: Mohamed
authors.initials: M
authors.lastname: Jebbar
authors.forename: Alain
authors.initials: A
authors.lastname: Dufour
references.citation: Int J Med Microbiol. 2006 Apr;296(2-3):73-81
references.pmid: 16476569
references.citation: Mol Microbiol. 2001 May;40(3):708-18
references.pmid: 11359576
references.citation: J Bacteriol. 2006 Dec;188(24):8601-6
references.pmid: 17028277
references.citation: PLoS Pathog. 2008 Sep 26;4(9):e1000166
references.pmid: 18818733
references.citation: Infect Immun. 2006 Jun;74(6):3134-47
references.pmid: 16714541
references.citation: J Bacteriol. 1989 May;171(5):2312-7
references.pmid: 2496102
references.citation: Mol Microbiol. 2003 Oct;50(1):29-43
references.pmid: 14507361
references.citation: J Bacteriol. 2008 Nov;190(21):7043-51
references.pmid: 18776012
references.citation: J Bacteriol. 2005 Jun;187(11):3630-5
references.pmid: 15901684
references.citation: J Bacteriol. 2002 Dec;184(23):6472-80
references.pmid: 12426334
references.citation: Int J Med Microbiol. 2006 Apr;296(2-3):83-91
references.pmid: 16483840
references.citation: J Proteome Res. 2008 Mar;7(3):1218-25
references.pmid: 18217705
references.citation: Proc Natl Acad Sci U S A. 1995 Jul 3;92(14):6424-8
references.pmid: 7604006
references.citation: J Ind Microbiol Biotechnol. 2007 Jan;34(1):5-8
references.pmid: 16491361
references.citation: Biochim Biophys Acta. 2000 May 31;1485(2-3):145-52
references.pmid: 10832095
references.citation: Mol Microbiol. 2003 Jul;49(2):401-10
references.pmid: 12828638
references.citation: J Bacteriol. 2000 May;182(10):2702-8
references.pmid: 10781536
references.citation: J Am Soc Mass Spectrom. 2004 Jun;15(6):862-9
references.pmid: 15144975
references.citation: FEMS Microbiol Lett. 1997 Aug 15;153(2):279-85
references.pmid: 9271853
references.citation: J Bacteriol. 2005 Jul;187(13):4372-80
references.pmid: 15968046
references.citation: Clin Microbiol Rev. 2002 Apr;15(2):194-222
references.pmid: 11932230
references.citation: Proc Natl Acad Sci U S A. 2004 Feb 3;101(5):1339-44
references.pmid: 14739337
references.citation: J Bacteriol. 1997 Sep;179(18):5756-67
references.pmid: 9294432
references.citation: Microbiology (Reading). 2009 Mar;155(Pt 3):712-723
references.pmid: 19246742
references.citation: FEMS Microbiol Rev. 2002 Mar;26(1):49-71
references.pmid: 12007642
references.citation: Mol Biosyst. 2008 Sep;4(9):882-8
references.pmid: 18704225
references.citation: Microbiology (Reading). 2006 May;152(Pt 5):1395-1406
references.pmid: 16622056
references.citation: Appl Environ Microbiol. 1993 Feb;59(2):473-8
references.pmid: 8434912
references.citation: J Chromatogr A. 2003 Jun 20;1002(1-2):79-92
references.pmid: 12885081
references.citation: J Bacteriol. 2002 Aug;184(15):4301-3
references.pmid: 12107149
references.citation: Curr Opin Microbiol. 2003 Feb;6(1):56-60
references.pmid: 12615220
references.citation: Appl Microbiol Biotechnol. 2005 Oct;68(6):718-25
references.pmid: 16160828
references.citation: Methods. 2001 Dec;25(4):402-8
references.pmid: 11846609
references.citation: Infect Immun. 2005 Feb;73(2):878-82
references.pmid: 15664929
references.citation: Environ Microbiol. 2005 Apr;7(4):459-71
references.pmid: 15816912
references.citation: FEMS Microbiol Lett. 2005 Dec 1;253(1):125-31
references.pmid: 16239086
references.citation: FEMS Microbiol Rev. 2006 Mar;30(2):274-91
references.pmid: 16472307