Burkholderia thailandensis harbors two identical rhl gene clusters responsible for the biosynthesis of rhamnolipids

Dubeau, Danielle; Déziel, Éric; Woods, Donald E. et Lépine, François (2009). Burkholderia thailandensis harbors two identical rhl gene clusters responsible for the biosynthesis of rhamnolipids BMC Microbiology , vol. 9 . pp. 1-12. DOI: 10.1186/1471-2180-9-263.

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Résumé

Background: Rhamnolipids are surface active mols. composed of rhamnose and β-hydroxydecanoic acid. These biosurfactants are produced mainly by Pseudomonas aeruginosa and have been thoroughly investigated since their early discovery. Recently, they have attracted renewed attention because of their involvement in various multicellular behaviors. Despite this high interest, only very few studies have focused on the prodn. of rhamnolipids by Burkholderia species. Results: Orthologs of rhlA, rhlB and rhlC, which are responsible for the biosynthesis of rhamnolipids in P. aeruginosa, have been found in the non-infectious Burkholderia thailandensis, as well as in the genetically similar important pathogen B. pseudomallei. In contrast to P. aeruginosa, both Burkholderia species contain these three genes necessary for rhamnolipid prodn. within a single gene cluster. Furthermore, two identical, paralogous copies of this gene cluster are found on the second chromosome of these bacteria. Both Burkholderia spp. produce rhamnolipids contg. 3-hydroxy fatty acid moieties with longer side chains than those described for P. aeruginosa. Addnl., the rhamnolipids produced by B. thailandensis contain a much larger proportion of dirhamnolipids vs. monorhamnolipids when compared to P. aeruginosa. The rhamnolipids produced by B. thailandensis reduce the surface tension of water to 42 mN/m while displaying a crit. micelle concn. value of 225 mg/L. Sep. mutations in both rhlA alleles, which are responsible for the synthesis of the rhamnolipid precursor 3-(3-hydroxyalkanoyloxy)alkanoic acid, prove that both copies of the rhl gene cluster are functional, but one contributes more to the total prodn. than the other. Finally, a double ΔrhlA mutant that is completely devoid of rhamnolipid prodn. is incapable of swarming motility, showing that both gene clusters contribute to this phenotype. Conclusions: Collectively, these results add another Burkholderia species to the list of bacteria able to produce rhamnolipids and this, by the means of two identical functional gene clusters. Our results also demonstrate the very impressive tensio-active properties these long-chain rhamnolipids possess in comparison to the well-studied short-chain ones from P. aeruginosa

Type de document:	Article
Mots-clés libres:	PSEUDOMONAS-AERUGINOSA RHAMNOLIPIDS, SERRATIA-LIQUEFACIENS MG1, GRAM-NEGATIVE BACTERIA, SWARMING MOTILITY, BIOSURFACTANT PRODUCTION, STRAIN 57RP, PSEUDOMALLEI, MUTAGENESIS, SYSTEM, DUPLICATION
Centre:	Centre INRS-Institut Armand Frappier
Date de dépôt:	01 mai 2014 15:11
Dernière modification:	01 mai 2014 15:11
URI:	https://espace.inrs.ca/id/eprint/2219

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