title: Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157:H7.
abstract: The molecular mechanisms controlling expression of the long polar fimbriae 2 (Lpf2) of enterohemorrhagic Escherichia coli (EHEC) O157:H7 were evaluated. Primer extension was used to locate the lpfA2 transcriptional start site in EHEC strain EDL933 at 171 bp upstream of the lpfA2 start codon. Semi-quantitative RT-PCR demonstrated that the highest lpfA2 expression occurs between an OD600 of 1.0 and 1.2 in DMEM at pH 6.5 and 37 °C. The level of lpfA2 transcription at OD600 1.2 and pH 6.5 was four times greater than that at pH 7.2. Although lpfA2 expression was decreased under iron-depleted conditions, its expression was increased in a ferric-uptake-regulator (Fur) mutant strain. The lpfA2 transcript was 0.7 and 2 times more abundant in wt EHEC grown in DMEM pH 6.5 plus iron and MacConkey broth at 25 °C, respectively, than in DMEM at pH 6.5. The lpf2 expression in DMEM pH 6.5 plus iron and bile salts was 2.7 times more abundant than baseline conditions. Further, transcription in the EDL933∆fur was 0.6 and 0.8 times higher as compared with the wt strain grown in DMEM pH 6.5 plus iron and MacConkey broth, respectively. Electrophoretic mobility shift assays showed that purified Fur interacts with the lpf2 regulatory region, indicating that Fur repression is exerted by direct binding to the promoter region. In summary, we demonstrated that the EHEC lpf2 operon is regulated in response to temperature, pH, bile salts and iron, during the exponential phase of growth, and is controlled by Fur.
authors: Posgrado en Microbiología, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico; Licenciatura en Biomedicina, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico; Centro de Investigaciones en Ciencias Microbiológicas, Benemérita Universidad Autónoma de Puebla, Puebla, Mexico.
authors: Margarita M
authors: MM
authors: Arenas-Hernández
authors: Maricarmen
authors: M
authors: Rojas-López
authors: Abraham
authors: A
authors: Medrano-López
authors: Karen J
authors: KJ
authors: Nuñez-Reza
authors: José Luis
authors: JL
authors: Puente
authors: Ygnacio
authors: Y
authors: Martínez-Laguna
authors: Alfredo G
authors: AG
authors: Torres
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001647:Bile Acids and Salts / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D019453:Escherichia coli O157 / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects*; D029968:Escherichia coli Proteins / Q000235:genetics*; D036781:Fimbriae Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects* / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012194:RNA-Directed DNA Polymerase; D012097:Repressor Proteins / Q000378:metabolism; D013696:Temperature; D024363:Transcription Initiation Site
chemical_list: D001426:Bacterial Proteins; D001647:Bile Acids and Salts; D003470:Culture Media; D029968:Escherichia coli Proteins; C000588669:LpfA protein, E coli; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D036781:Fimbriae Proteins; D007501:Iron; D012194:RNA-Directed DNA Polymerase
keywords: ferric-uptake-regulator; long polar 2 fimbriae; lpf2 operon