Document Detail

rhlA is required for the production of a novel biosurfactant promoting swarming motility in Pseudomonas aeruginosa: 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs), the precursors of rhamnolipids.
MedLine Citation:
PMID:  12904540     Owner:  NLM     Status:  MEDLINE    
Pseudomonas aeruginosa produces extracellular glycolipids composed of L-rhamnose and 3-hydroxyalkanoic acid called rhamnolipids. Although these compounds are usually regarded as biosurfactants or haemolysins, their exact physiological function is not well understood. Rhamnolipids are synthesized by a rhamnosyltransferase, encoded by the rhlAB operon, which catalyses the transfer of TDP-L-rhamnose to 3-(3-hydroxyalkanoyloxy)alkanoic acid (HAA) moieties of various lengths. RhlB is the catalytic protein of the rhamnosyltransferase. rhlA is indispensable for rhamnolipid synthesis, but its function is unknown. Using a liquid chromatography/mass spectrometry method, the production of extracellular HAAs by P. aeruginosa was detected previously and it was demonstrated that they are the actual precursors of rhamnolipid biosynthesis. In this report, evidence is presented indicating that rhlA is required for production of HAAs and that these HAAs display potent surface-active properties. P. aeruginosa can colonize surfaces by swarming motility, a form of organized translocation requiring the production of wetting agents. Using rhlA and rhlB mutants it was observed that swarming requires the expression of the rhlA gene but does not necessitate rhamnolipid production, as HAAs act as surfactants. Finally, it was shown that the use of ammonium instead of nitrate as source of nitrogen and an excess of available iron both decrease rhlA expression and swarming motility.
Eric Déziel; François Lépine; Sylvain Milot; Richard Villemur
Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  149     ISSN:  1350-0872     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2003 Aug 
Date Detail:
Created Date:  2003-08-07     Completed Date:  2003-10-23     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  England    
Other Details:
Languages:  eng     Pagination:  2005-13     Citation Subset:  IM    
INRS-Institut Armand-Frappier, Laval, Québec, Canada H7V 1B7.
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MeSH Terms
Bacterial Proteins*
Gene Expression
Genes, Bacterial
Glycolipids / chemistry,  metabolism*
Hexosyltransferases / genetics*,  metabolism*
Molecular Structure
Pseudomonas aeruginosa / genetics*,  physiology*
Surface-Active Agents / chemistry,  metabolism*
Reg. No./Substance:
0/Bacterial Proteins; 0/Glycolipids; 0/Surface-Active Agents; EC 2.4.1.-/Hexosyltransferases; EC 2.4.1.-/rhamnosyltransferase 1

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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