title: The Pseudomonas aeruginosa rmlBDAC operon, encoding dTDP-L-rhamnose biosynthetic enzymes, is regulated by the quorum-sensing transcriptional regulator RhlR and the alternative sigma factor σS.
abstract: Pseudomonas aeruginosa produces as biosurfactants rhamnolipids, containing one (mono-rhamnolipid) or two (di-rhamnolipid) l-rhamnose molecules. The rhamnosyltransferase RhlB catalyses the synthesis of mono-rhamnolipid using as precursors dTDP-l-rhamnose and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) produced by RhlA, while the rhamnosyltransferase RhlC synthesizes di-rhamnolipid using mono-rhamnolipid and dTDP-l-rhamnose as substrates. The Las and Rhl quorum-sensing systems coordinately regulate the production of these surfactants, as well as that of other exoproducts involved in bacterial virulence, at the transcriptional level in a cell density-dependent manner. In this work we study the transcriptional regulation of the rmlBDAC operon, encoding the enzymes involved in the production of dTDP-l-rhamnose, the substrate of both rhamnosyltransferases, RhlB and RhlC, and also a component of P. aeruginosa lipopolysaccharide. Here we show that the rmlBDAC operon possesses three promoters. One of these transcriptional start sites (P2) is responsible for most of its expression and is dependent on the stationary phase sigma factor σ(S) and on RhlR/C(4)-HSL through its binding to an atypical 'las box'.
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México.
authors.forename: Marisela
authors.initials: M
authors.lastname: Aguirre-Ramírez
authors.affiliation: Universidad Autónoma de Baja California, Mexicali, BC, México.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Medina
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México.
authors.forename: Abigail
authors.initials: A
authors.lastname: González-Valdez
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México.
authors.forename: Victoria
authors.initials: V
authors.lastname: Grosso-Becerra
authors.affiliation: Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México.
authors.forename: Gloria
authors.initials: G
authors.lastname: Soberón-Chávez
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009702:Nucleoside Diphosphate Sugars / Q000096:biosynthesis; D009876:Operon; D011401:Promoter Regions, Genetic; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000235:genetics*; D053038:Quorum Sensing / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000096:biosynthesis; D024363:Transcription Initiation Site
chemical_list: D001426:Bacterial Proteins; D009702:Nucleoside Diphosphate Sugars; C086515:RhlR protein, Pseudomonas aeruginosa; D012808:Sigma Factor; D013942:Thymine Nucleotides; C069567:sigma factor KatF protein, Bacteria; C073293:thymidine diphosphate rhamnose