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Synthesis of multiple exoproducts in Pseudomonas aeruginosa is under the control of RhlR-RhlI, another set of regulators in strain PAO1 with homology to the autoinducer-responsive LuxR-LuxI family.
J Bacteriol. 1995 Dec; 177(24):7155-63.JB

Abstract

Mutants of Pseudomonas aeruginosa PAO1 that were deficient in the ability to produce proteases that degrade casein were detected among the survivors of chemical mutagenesis. One such mutant (PDO31) showed reduced production of elastolytic activity, beta-hemolytic activity, and pyocyanin. A 4.3-kb EcoRI fragment from a gene bank of PAO1 that complemented defects in PDO31 was found. Transposon mutagenesis and deletion derivatives of the clone were used in conjunction with complementation tests to determine the physical location of the gene of interest. Nucleotide sequence analysis revealed an open reading frame (rhlR) encoding a putative 27.6-kDa protein (RhlR) with homology to autoinducer-responsive regulators of quorum sensing systems such as LuxR of Vibrio fischeri and LasR of P. aeruginosa. Further sequence analysis downstream of rhlR revealed an independently transcribed gene (rhlI) that encodes a putative 22.2-kDa protein with homology to members of the family of autoinducer synthetases, such as LuxI of V. fischeri and LasI of P. aeruginosa. The rhlRI sequences were also recently reported by others (U.A. Ochsner and J. Reiser, Proc. Natl. Acad. Sci. USA 92: 6424-6428, 1995) as an autoinducer-mediated regulation mechanism for rhamnolipid biosurfactant synthesis in P. aeruginosa PG201. Mutants with defects in rhlR or rhlI were constructed in PAO1 by gene replacement, using clones modified by Tn501 insertion. Compared with the wild type, the rhlR and rhlI mutants both showed defects in the production of elastase, LasA protease, rhamnolipid, and pyocyanin. Transcription from the gene for elastase, as measured with a lasB-cat fusion, demonstrated that production of elastase was subject to cell density-dependent gene activation in PAO1. However, transcription of lasB-cat in the rhlI mutant, which had lost the presumptive autoinducer synthetase (predicted to activate RhlR), showed low basal activity and had lost all cell density-dependent transcription of lasB. Thus, RhlR-RhlI represent the second autoinducer-responsive regulatory mechanism found in P. aeruginosa that controls expression of multiple virulence factor exoproducts, including elastase.

Authors+Show Affiliations

Department of Medicine, University of Tennessee, Memphis, USA.No affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

8522523

Citation

Brint, J M., and D E. Ohman. "Synthesis of Multiple Exoproducts in Pseudomonas Aeruginosa Is Under the Control of RhlR-RhlI, Another Set of Regulators in Strain PAO1 With Homology to the Autoinducer-responsive LuxR-LuxI Family." Journal of Bacteriology, vol. 177, no. 24, 1995, pp. 7155-63.
Brint JM, Ohman DE. Synthesis of multiple exoproducts in Pseudomonas aeruginosa is under the control of RhlR-RhlI, another set of regulators in strain PAO1 with homology to the autoinducer-responsive LuxR-LuxI family. J Bacteriol. 1995;177(24):7155-63.
Brint, J. M., & Ohman, D. E. (1995). Synthesis of multiple exoproducts in Pseudomonas aeruginosa is under the control of RhlR-RhlI, another set of regulators in strain PAO1 with homology to the autoinducer-responsive LuxR-LuxI family. Journal of Bacteriology, 177(24), 7155-63.
Brint JM, Ohman DE. Synthesis of Multiple Exoproducts in Pseudomonas Aeruginosa Is Under the Control of RhlR-RhlI, Another Set of Regulators in Strain PAO1 With Homology to the Autoinducer-responsive LuxR-LuxI Family. J Bacteriol. 1995;177(24):7155-63. PubMed PMID: 8522523.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Synthesis of multiple exoproducts in Pseudomonas aeruginosa is under the control of RhlR-RhlI, another set of regulators in strain PAO1 with homology to the autoinducer-responsive LuxR-LuxI family. AU - Brint,J M, AU - Ohman,D E, PY - 1995/12/1/pubmed PY - 1995/12/1/medline PY - 1995/12/1/entrez SP - 7155 EP - 63 JF - Journal of bacteriology JO - J. Bacteriol. VL - 177 IS - 24 N2 - Mutants of Pseudomonas aeruginosa PAO1 that were deficient in the ability to produce proteases that degrade casein were detected among the survivors of chemical mutagenesis. One such mutant (PDO31) showed reduced production of elastolytic activity, beta-hemolytic activity, and pyocyanin. A 4.3-kb EcoRI fragment from a gene bank of PAO1 that complemented defects in PDO31 was found. Transposon mutagenesis and deletion derivatives of the clone were used in conjunction with complementation tests to determine the physical location of the gene of interest. Nucleotide sequence analysis revealed an open reading frame (rhlR) encoding a putative 27.6-kDa protein (RhlR) with homology to autoinducer-responsive regulators of quorum sensing systems such as LuxR of Vibrio fischeri and LasR of P. aeruginosa. Further sequence analysis downstream of rhlR revealed an independently transcribed gene (rhlI) that encodes a putative 22.2-kDa protein with homology to members of the family of autoinducer synthetases, such as LuxI of V. fischeri and LasI of P. aeruginosa. The rhlRI sequences were also recently reported by others (U.A. Ochsner and J. Reiser, Proc. Natl. Acad. Sci. USA 92: 6424-6428, 1995) as an autoinducer-mediated regulation mechanism for rhamnolipid biosurfactant synthesis in P. aeruginosa PG201. Mutants with defects in rhlR or rhlI were constructed in PAO1 by gene replacement, using clones modified by Tn501 insertion. Compared with the wild type, the rhlR and rhlI mutants both showed defects in the production of elastase, LasA protease, rhamnolipid, and pyocyanin. Transcription from the gene for elastase, as measured with a lasB-cat fusion, demonstrated that production of elastase was subject to cell density-dependent gene activation in PAO1. However, transcription of lasB-cat in the rhlI mutant, which had lost the presumptive autoinducer synthetase (predicted to activate RhlR), showed low basal activity and had lost all cell density-dependent transcription of lasB. Thus, RhlR-RhlI represent the second autoinducer-responsive regulatory mechanism found in P. aeruginosa that controls expression of multiple virulence factor exoproducts, including elastase. SN - 0021-9193 UR - https://www.unboundmedicine.com/medline/citation/8522523/Synthesis_of_multiple_exoproducts_in_Pseudomonas_aeruginosa_is_under_the_control_of_RhlR_RhlI_another_set_of_regulators_in_strain_PAO1_with_homology_to_the_autoinducer_responsive_LuxR_LuxI_family_ L2 - http://jb.asm.org/cgi/pmidlookup?view=long&pmid=8522523 DB - PRIME DP - Unbound Medicine ER -