title: Transcriptional activation of the Azotobacter vinelandii polyhydroxybutyrate biosynthetic genes phbBAC by PhbR and RpoS.
abstract: We previously showed that in Azotobacter vinelandii, accumulation of polyhydroxybutyrate (PHB) occurs mainly during the stationary phase, and that a mutation in phbR, encoding a transcriptional regulator of the AraC family, reduces PHB accumulation. In this study, we characterized the roles of PhbR and RpoS, a central regulator during stationary phase in bacteria, in the regulation of expression of the PHB biosynthetic operon phbBAC and phbR. We showed that inactivation of rpoS reduced PHB accumulation, similar to the phbR mutation, and inactivation of both rpoS and phbR resulted in an inability to produce PHB. We carried out expression studies with the wild-type, and the rpoS, phbR and double rpoS-phbR mutant strains, using quantitative RT-PCR, as well as phbB : : gusA and phbR : : gusA gene fusions. These studies showed that both PhbR and RpoS act as activators of phbB and phbR, and revealed a role for PhbR as an autoactivator. We also demonstrated that PhbR binds specifically to two almost identical 18 bp sites, TGTCACCAA-N(4)-CACTA and TGTCACCAA-N(4)-CAGTA, present in the phbB promoter region. The activation of phbB and phbR transcription by RpoS reported here is in agreement with the observation that accumulation of PHB in A. vinelandii occurs mainly during the stationary phase.
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Alberto
authors.initials: A
authors.lastname: Hernandez-Eligio
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Mildred
authors.initials: M
authors.lastname: Castellanos
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Soledad
authors.initials: S
authors.lastname: Moreno
authors.affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Espín
mesh_terms: D016948:Azotobacter vinelandii / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D006885:Hydroxybutyrates / Q000378:metabolism*; D009154:Mutation; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006885:Hydroxybutyrates; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria