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Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes.
J Bacteriol. 1997 Sep; 179(18):5756-67.JB

Abstract

Two quorum-sensing systems (las and rhl) regulate virulence gene expression in Pseudomonas aeruginosa. The las system consists of a transcriptional activator, LasR, and LasI, which directs the synthesis of the autoinducer N-(3-oxododecanoyl) homoserine lactone (PAI-1). Induction of lasB (encoding elastase) and other virulence genes requires LasR and PAI-1. The rhl system consists of a putative transcriptional activator, RhlR, and RhlI, which directs the synthesis of N-butyryl homoserine lactone (PAI-2). Rhamnolipid production in P. aeruginosa has been reported to require both the rhl system and rhlAB (encoding a rhamnosyltransferase). Here we report the generation of a delta lasI mutant and both delta lasI delta rhlI and delta lasR rhlR::Tn501 double mutants of strain PAO1. Rhamnolipid production and elastolysis were reduced in the delta lasI single mutant and abolished in the double-mutant strains. rhlAB mRNA was not detected in these strains at mid-logarithmic phase but was abundant in the parental strain. Further RNA analysis of the wild-type strain revealed that rhlAB is organized as an operon. The rhlAB transcriptional start was mapped, and putative sigma 54 and sigma 70 promoters were identified upstream. To define components required for rhlAB expression, we developed a bioassay in Escherichia coli and demonstrated that PAI-2 and RhlR are required and sufficient for expression of rhlA. To characterize the putative interaction between PAI-2 and RhlR, we demonstrated that [3H]PAI-2 binds to E. coli cells expressing RhlR and not to those expressing LasR. Finally, the specificity of the las and rhl systems was examined in E. coli bioassays. The las system was capable of mildly activating rhlA, and similarly, the rhl system partly activated lasB. However; these effects were much less than the activation of rhlA by the rhl system and lasB by the las system. The results presented here further characterize the roles of the rhl and las quorum-sensing systems in virulence gene expression.

Authors+Show Affiliations

Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9294432

Citation

Pearson, J P., et al. "Roles of Pseudomonas Aeruginosa Las and Rhl Quorum-sensing Systems in Control of Elastase and Rhamnolipid Biosynthesis Genes." Journal of Bacteriology, vol. 179, no. 18, 1997, pp. 5756-67.
Pearson JP, Pesci EC, Iglewski BH. Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes. J Bacteriol. 1997;179(18):5756-67.
Pearson, J. P., Pesci, E. C., & Iglewski, B. H. (1997). Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes. Journal of Bacteriology, 179(18), 5756-67.
Pearson JP, Pesci EC, Iglewski BH. Roles of Pseudomonas Aeruginosa Las and Rhl Quorum-sensing Systems in Control of Elastase and Rhamnolipid Biosynthesis Genes. J Bacteriol. 1997;179(18):5756-67. PubMed PMID: 9294432.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes. AU - Pearson,J P, AU - Pesci,E C, AU - Iglewski,B H, PY - 1997/9/19/pubmed PY - 1997/9/19/medline PY - 1997/9/19/entrez SP - 5756 EP - 67 JF - Journal of bacteriology JO - J. Bacteriol. VL - 179 IS - 18 N2 - Two quorum-sensing systems (las and rhl) regulate virulence gene expression in Pseudomonas aeruginosa. The las system consists of a transcriptional activator, LasR, and LasI, which directs the synthesis of the autoinducer N-(3-oxododecanoyl) homoserine lactone (PAI-1). Induction of lasB (encoding elastase) and other virulence genes requires LasR and PAI-1. The rhl system consists of a putative transcriptional activator, RhlR, and RhlI, which directs the synthesis of N-butyryl homoserine lactone (PAI-2). Rhamnolipid production in P. aeruginosa has been reported to require both the rhl system and rhlAB (encoding a rhamnosyltransferase). Here we report the generation of a delta lasI mutant and both delta lasI delta rhlI and delta lasR rhlR::Tn501 double mutants of strain PAO1. Rhamnolipid production and elastolysis were reduced in the delta lasI single mutant and abolished in the double-mutant strains. rhlAB mRNA was not detected in these strains at mid-logarithmic phase but was abundant in the parental strain. Further RNA analysis of the wild-type strain revealed that rhlAB is organized as an operon. The rhlAB transcriptional start was mapped, and putative sigma 54 and sigma 70 promoters were identified upstream. To define components required for rhlAB expression, we developed a bioassay in Escherichia coli and demonstrated that PAI-2 and RhlR are required and sufficient for expression of rhlA. To characterize the putative interaction between PAI-2 and RhlR, we demonstrated that [3H]PAI-2 binds to E. coli cells expressing RhlR and not to those expressing LasR. Finally, the specificity of the las and rhl systems was examined in E. coli bioassays. The las system was capable of mildly activating rhlA, and similarly, the rhl system partly activated lasB. However; these effects were much less than the activation of rhlA by the rhl system and lasB by the las system. The results presented here further characterize the roles of the rhl and las quorum-sensing systems in virulence gene expression. SN - 0021-9193 UR - https://www.unboundmedicine.com/medline/citation/9294432/Roles_of_Pseudomonas_aeruginosa_las_and_rhl_quorum_sensing_systems_in_control_of_elastase_and_rhamnolipid_biosynthesis_genes_ L2 - http://jb.asm.org/cgi/pmidlookup?view=long&pmid=9294432 DB - PRIME DP - Unbound Medicine ER -