Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157: H7

Margarita M. Arenas-Hernández, Maricarmen Rojas-López, Abraham Medrano-López, Karen J. Nuñez-Reza, José Luis Puente, Ygnacio Martínez-Laguna, Alfredo Torres

Research output: Contribution to journalArticle

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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 OD<inf>600</inf> of 1.0 and 1.2 in DMEM at pH 6.5 and 37 °C. The level of lpfA2 transcription at OD<inf>600</inf> 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{increment}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.

Original languageEnglish (US)
Pages (from-to)105-114
Number of pages10
JournalFEMS Microbiology Letters
Volume357
Issue number2
DOIs
StatePublished - 2014

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Enterohemorrhagic Escherichia coli
Escherichia coli O157
Iron
Bile Acids and Salts
Initiator Codon
Nucleic Acid Regulatory Sequences
Electrophoretic Mobility Shift Assay
Operon
Genetic Promoter Regions
Polymerase Chain Reaction
Temperature

Keywords

  • Ferric-uptake-regulator
  • Long polar 2 fimbriae
  • lpf2 operon

ASJC Scopus subject areas

  • Microbiology
  • Genetics
  • Molecular Biology
  • Medicine(all)

Cite this

Arenas-Hernández, M. M., Rojas-López, M., Medrano-López, A., Nuñez-Reza, K. J., Puente, J. L., Martínez-Laguna, Y., & Torres, A. (2014). Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157: H7. FEMS Microbiology Letters, 357(2), 105-114. https://doi.org/10.1111/1574-6968.12513

Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157 : H7. / Arenas-Hernández, Margarita M.; Rojas-López, Maricarmen; Medrano-López, Abraham; Nuñez-Reza, Karen J.; Puente, José Luis; Martínez-Laguna, Ygnacio; Torres, Alfredo.

In: FEMS Microbiology Letters, Vol. 357, No. 2, 2014, p. 105-114.

Research output: Contribution to journalArticle

Arenas-Hernández, MM, Rojas-López, M, Medrano-López, A, Nuñez-Reza, KJ, Puente, JL, Martínez-Laguna, Y & Torres, A 2014, 'Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157: H7', FEMS Microbiology Letters, vol. 357, no. 2, pp. 105-114. https://doi.org/10.1111/1574-6968.12513
Arenas-Hernández MM, Rojas-López M, Medrano-López A, Nuñez-Reza KJ, Puente JL, Martínez-Laguna Y et al. Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157: H7. FEMS Microbiology Letters. 2014;357(2):105-114. https://doi.org/10.1111/1574-6968.12513
Arenas-Hernández, Margarita M. ; Rojas-López, Maricarmen ; Medrano-López, Abraham ; Nuñez-Reza, Karen J. ; Puente, José Luis ; Martínez-Laguna, Ygnacio ; Torres, Alfredo. / Environmental regulation of the long polar fimbriae 2 of enterohemorrhagic Escherichia coli O157 : H7. In: FEMS Microbiology Letters. 2014 ; Vol. 357, No. 2. pp. 105-114.
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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{increment}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.",
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