Expression of the Escherichia coli ompW colicin S4 receptor gene is regulated by temperature and modulated by the H-NS and StpA nucleoid-associated proteins

Authors

  • Luciano Brambilla,

    1. Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina
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  • Jorgelina Morán-Barrio,

    1. Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina
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  • Alejandro M. Viale

    Corresponding author
    1. Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina
    • Correspondence: Alejandro M. Viale, IBR, Suipacha 590, 2000 Rosario, Argentina. Tel.: 54 341 4350661; fax: 54 341 4390465; e-mail: viale@ibr-conicet.gov.ar

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Abstract

The OmpW family consists of a ubiquitous group of small outer membrane (OM) β-barrel proteins of Gram-negative bacteria with proposed roles in environmental adaptation but poorly understood mechanisms of expression. We report here that Escherichia coli K-12 OmpW contents are drastically modified by temperature changes compatible with the leap from the environment to warm-blooded hosts and/or vice versa. Thus, while OmpW is present in the OM of bacteria grown at 37 °C, it sharply disappears at 23 °C with the concomitant acquisition of colicin S4 resistance by the cells. ompW::lacZY fusions indicated that temperature regulation operates at the level of transcription, being ompW expression almost abolished at 23 °C as compared to 37 °C. Moreover, E. coli Δhns mutants lacking H-NS showed reductions in ompW transcription and OmpW contents at 37 °C, indicating positive modulatory roles for this nucleoid-structuring protein in ompW expression. Also, ΔhnsΔstpA double mutants simultaneously lacking H-NS and its paralog StpA showed more severe reductions in ompW expression at 37 °C, resulting in the complete loss of OmpW. The overall results indicate that OmpW contents in E. coli are regulated by both temperature and H-NS and reinforce OmpW functions in bacterial adaptation to warm-blooded hosts.

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