Quorum sensing is a regulatory process used by bacteria for controlling gene expression in response to increasing cell density.[1] This regulatory process manifests itself with a variety of phenotypes including biofilm formation and virulence factor production.[2] Coordinated gene expression is achieved by the production, release, and detection of small diffusible signal molecules called autoinducers. The N-acylated homoserine lactones (AHLs) comprise one such class of autoinducers, each of which generally consists of a fatty acid coupled with homoserine lactone (HSL). AHLs vary in acyl group length (C4-C18), in the substitution of C3 (hydrogen, hydroxyl, or oxo group) and in the presence or absence of one or more carbon-carbon double bonds in the fatty acid chain. These differences confer signal specificity through the affinity of transcriptional regulators of the LuxR family.[3] C16:1-Δ9-(L)-HSL is a long-chain AHL that functions as a quorum sensing signaling molecule in strains of S. meliloti.[4],[5],[6],[7] Regulating bacterial quorum sensing signaling can be used to inhibit pathogenesis and thus, represents a new approach to antimicrobial therapy in the treatment of infectious diseases.[8]
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[1]. González, J.E., and Keshavan, N.D. Messing with bacterial quorum sensing. Microbiol. Mol. Biol. Rev. 70(4), 859-875 (2006).
[2]. Gould, T.A., Herman, J., Krank, J., et al. Specificity of acyl-homoserine lactone syntheses examined by mass spectrometry. J. Bacteriol. 188(2), 773-783 (2006).
[3]. Penalver, C.G.N., Morin, D., Cantet, F., et al. Methylobacterium extorquens AM1 produces a novel type of acyl-homoserine lactone with a double unsaturated side chain under methylotrophic growth conditions. FEBS Lett. 580(2), 561-567 (2006).
[4]. Teplitski, M., Eberhard, A., Gronquist, M.R., et al. Chemical identification of N-acyl homoserine lactone quorum-sensing signals produced by Sinorhizobium meliloti strains in defined medium. Archives of Microbiology 180, 494-497 (2003).
[5]. Gao, M., Chen, H., Eberhard, A., et al. sinI- and expR-dependent quorum sensing in Sinorhizobium meliloti. Journal of Bacteriology 187(23), 7931-7944 (2005).
[6]. Marketon, M.M., Glenn, S.A., Eberhard, A., et al. Quorum sensing controls exopolysaccharide production in Sinorhizobium meliloti. Journal of Bacteriology 185(1), 325-331 (2003).
[7]. Marketon, M., Gronquist, M.R., Eberhard, A., et al. Characterization of the Sinorhizobium meliloti sinR/sinI locus and the production of novel N-Acyl homoserine lactones. Journal of Bacteriology 184(20), 5686-5695 (2002).
[8]. Cegelski, L., Marshall, G.R., Eldridge, G.R., et al. The biology and future prospects of antivirulence therapies. Nat. Rev. Microbiol. 6(1), 17-27 (2008).