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Gene Review

lasI  -  autoinducer synthesis protein LasI

Pseudomonas aeruginosa PAO1

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Disease relevance of lasI

  • Biofilms were grown from wild-type (WT) Pseudomonas aeruginosa PAO1 and the cell signaling lasI mutant PAO1-JP1 under laminar and turbulent flows to investigate the relative contributions of hydrodynamics and cell signaling for biofilm formation [1].
  • Although recombinant E. coli cells containing the PAI synthase gene, lasI, produce PAI, these cells do not produce factor 2 [2].
  • The interchangeability of the P. aeruginosa and Vibrio fischeri homologs LasR and LuxR and their respective autoinducers, PAI and VAI, as activators of lasI-lacZ was examined [3].

High impact information on lasI

  • A specific signaling mutant, a lasI mutant, forms flat, undifferentiated biofilms that unlike wild-type biofilms are sensitive to the biocide sodium dodecyl sulfate [4].
  • These results suggest that PtxR negatively regulates the expression of the rhamnolipid and pyocyanin genes through rhlI and the pqsABCDE operon while it positively regulates the expression of lasB through lasI [5].
  • The expression of the RhlI synthase gene rhlI and the production of the C(4)-HSL autoinducer were increased in the ptxR mutant, while the expression of the LasI synthase gene lasI and the production of 3OC(12)-HSL were reduced [5].
  • In particular, the expression of lasI, rhlI and rhlR, which encode key components of the las and rhl quorum-sensing (QS) systems, were significantly decreased in the pprB mutant [6].
  • These two systems, the lasI-lasR and rhII-rhIR gene pairs, are members of the luxI-luxR family of quorum-sensing signal generators and signal receptors [7].

Chemical compound and disease context of lasI

  • A lasI mutant of Pseudomonas aeruginosa was only able to tolerate 0.1% CTAB on Luria-Bertani agar plates but could tolerate 5% CTAB when supplemented with homoserine lactone containing culture supernatants [8].

Biological context of lasI

  • Variations in biofilm formation by, and antibiotic resistance of, Pseudomonas aeruginosa PAO1 (wild type) and the quorum-sensing-deficient mutants PDO100 (Delta rhlI), JP1 (Delta lasI) and JP2 (Delta lasI Delta rhlI) were studied [9].
  • The rhlI mutant PDO100 and rhlR mutant PDO111, but not the lasI mutant PDO-JP1, showed approximately twofold upregulation of the exoS'-gfp reporter in comparison to PAO1 [10].
  • The aim of this study was to develop a real time RT-PCR method for the direct quantification of the transcripts of three P. aeruginosa virulence genes: exoS, lasI and algD, during the first seven days of a rat lung infection [11].
  • The presence of any of these plasmids within the lasI rhlI double mutant significantly enhanced its in vivo virulence, as well as its ability to spread within the burned skin [12].
  • The DNA binding site of the RsaL protein on the rsaL-lasI bidirectional promoter partially overlaps the binding site of the LasR protein, consistent with the hypothesis that RsaL and LasR could be in binding competition on this promoter [13].

Associations of lasI with chemical compounds

  • Such mutants also produce less acylated homoserine lactone autoinducer PAI-1, consistent with an observed reduction in lasI expression [14].
  • Unlike planktonic bacteria, Mn-SOD was constitutive in the lasI and lasR mutant biofilms but could be suppressed if the growth medium was amended with 25 microM ferric chloride [15].

Other interactions of lasI

  • The autoinducer synthetase genes lasI and rhlI and the regulatory genes mexT and mexS were characterized by DNA sequencing [16].
  • Four strains of Pseudomonas aeruginosa (wild type, Delta(pil)HIJK mutant, lasI mutant, and rpoS mutant) were genetically tagged with the green fluorescent protein, and the development of flow chamber-grown biofilms by each of them was investigated by confocal laser scanning microscopy [17].
  • Expression of the genes vsmR, lasI, and PA4296 was studied by use of reverse transcriptase and subsequent quantitative real-time PCR of the cDNAs [18].

Analytical, diagnostic and therapeutic context of lasI

  • To further elucidate the contribution of lasI and rhlI to biofilm maturation, we utilized fusions to unstable green fluorescent protein in concert with confocal microscopy to perform real-time temporal and spatial studies of these genes in a flowing environment [19].
  • In this study, we compared the protein patterns of the intracellular, extracellular and surface protein fractions of the PAO1 parent strain with those of an isogenic lasI rhlI double mutant by means of two-dimensional gel electrophoresis (2-DE) [20].
  • Liquid chromatograph-tandem mass spectrometry and thin-layer chromatography confirmed products of lasI and yenI activity in single and cotransformants [21].


  1. Influence of hydrodynamics and cell signaling on the structure and behavior of Pseudomonas aeruginosa biofilms. Purevdorj, B., Costerton, J.W., Stoodley, P. Appl. Environ. Microbiol. (2002) [Pubmed]
  2. A second N-acylhomoserine lactone signal produced by Pseudomonas aeruginosa. Pearson, J.P., Passador, L., Iglewski, B.H., Greenberg, E.P. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  3. Activation of the Pseudomonas aeruginosa lasI gene by LasR and the Pseudomonas autoinducer PAI: an autoinduction regulatory hierarchy. Seed, P.C., Passador, L., Iglewski, B.H. J. Bacteriol. (1995) [Pubmed]
  4. The involvement of cell-to-cell signals in the development of a bacterial biofilm. Davies, D.G., Parsek, M.R., Pearson, J.P., Iglewski, B.H., Costerton, J.W., Greenberg, E.P. Science (1998) [Pubmed]
  5. PtxR modulates the expression of QS-controlled virulence factors in the Pseudomonas aeruginosa strain PAO1. Carty, N.L., Layland, N., Colmer-Hamood, J.A., Calfee, M.W., Pesci, E.C., Hamood, A.N. Mol. Microbiol. (2006) [Pubmed]
  6. The two-component response regulator PprB modulates quorum-sensing signal production and global gene expression in Pseudomonas aeruginosa. Dong, Y.H., Zhang, X.F., Soo, H.M., Greenberg, E.P., Zhang, L.H. Mol. Microbiol. (2005) [Pubmed]
  7. Analysis of random and site-directed mutations in rhII, a Pseudomonas aeruginosa gene encoding an acylhomoserine lactone synthase. Parsek, M.R., Schaefer, A.L., Greenberg, E.P. Mol. Microbiol. (1997) [Pubmed]
  8. Eight gram-negative bacteria are 10,000 times more sensitive to cationic detergents than to anionic detergents. Rajagopal, S., Eis, N., Nickerson, K.W. Can. J. Microbiol. (2003) [Pubmed]
  9. Effects of quorum-sensing deficiency on Pseudomonas aeruginosa biofilm formation and antibiotic resistance. Shih, P.C., Huang, C.T. J. Antimicrob. Chemother. (2002) [Pubmed]
  10. Expression of Pseudomonas aeruginosa exoS is controlled by quorum sensing and RpoS. Hogardt, M., Roeder, M., Schreff, A.M., Eberl, L., Heesemann, J. Microbiology (Reading, Engl.) (2004) [Pubmed]
  11. Relative expression of Pseudomonas aeruginosa virulence genes analyzed by a real time RT-PCR method during lung infection in rats. Joly, B., Béatrice, J., Pierre, M., Maud, P., Auvin, S., Stéphane, A., Colin, F., Franc Cois, C., Gottrand, F., Frédéric, G., Guery, B., Benoit, G., Husson, M.O. FEMS Microbiol. Lett. (2005) [Pubmed]
  12. Contribution of quorum sensing to the virulence of Pseudomonas aeruginosa in burn wound infections. Rumbaugh, K.P., Griswold, J.A., Iglewski, B.H., Hamood, A.N. Infect. Immun. (1999) [Pubmed]
  13. The quorum-sensing negative regulator RsaL of Pseudomonas aeruginosa binds to the lasI promoter. Rampioni, G., Bertani, I., Zennaro, E., Polticelli, F., Venturi, V., Leoni, L. J. Bacteriol. (2006) [Pubmed]
  14. Influence of the MexAB-OprM multidrug efflux system on quorum sensing in Pseudomonas aeruginosa. Evans, K., Passador, L., Srikumar, R., Tsang, E., Nezezon, J., Poole, K. J. Bacteriol. (1998) [Pubmed]
  15. Gene expression in Pseudomonas aeruginosa: evidence of iron override effects on quorum sensing and biofilm-specific gene regulation. Bollinger, N., Hassett, D.J., Iglewski, B.H., Costerton, J.W., McDermott, T.R. J. Bacteriol. (2001) [Pubmed]
  16. Expression of the las and rhl quorum-sensing systems in clinical isolates of Pseudomonas aeruginosa does not correlate with efflux pump expression or antimicrobial resistance. Bratu, S., Gupta, J., Quale, J. J. Antimicrob. Chemother. (2006) [Pubmed]
  17. Statistical analysis of Pseudomonas aeruginosa biofilm development: impact of mutations in genes involved in twitching motility, cell-to-cell signaling, and stationary-phase sigma factor expression. Heydorn, A., Ersbøll, B., Kato, J., Hentzer, M., Parsek, M.R., Tolker-Nielsen, T., Givskov, M., Molin, S. Appl. Environ. Microbiol. (2002) [Pubmed]
  18. Use of quantitative real-time RT-PCR to analyse the expression of some quorum-sensing regulated genes in Pseudomonas aeruginosa. Schwartz, T., Walter, S., Marten, S.M., Kirschh??fer, F., Nusser, M., Obst, U. Analytical and bioanalytical chemistry (2007) [Pubmed]
  19. Quorum-sensing genes in Pseudomonas aeruginosa biofilms: their role and expression patterns. De Kievit, T.R., Gillis, R., Marx, S., Brown, C., Iglewski, B.H. Appl. Environ. Microbiol. (2001) [Pubmed]
  20. Identification of quorum-sensing regulated proteins in the opportunistic pathogen Pseudomonas aeruginosa by proteomics. Arevalo-Ferro, C., Hentzer, M., Reil, G., Görg, A., Kjelleberg, S., Givskov, M., Riedel, K., Eberl, L. Environ. Microbiol. (2003) [Pubmed]
  21. Long- and short-chain plant-produced bacterial N-acyl-homoserine lactones become components of phyllosphere, rhizosphere, and soil. Scott, R.A., Weil, J., Le, P.T., Williams, P., Fray, R.G., von Bodman, S.B., Savka, M.A. Mol. Plant Microbe Interact. (2006) [Pubmed]
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