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A small RNA that regulates motility and biofilm formation in response to changes in nutrient availability in Escherichia coli

Authors

  • Maureen K. Thomason,

    1. Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
    2. Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC, USA.
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  • Fanette Fontaine,

    1. Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
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    • Present address: CNRS UPR9073, Institut de Biologie Physico-Chimique affiliated with Université Paris Diderot, Sorbonne Paris Cité, Paris, France.

  • Nicholas De Lay,

    1. Laboratory of Molecular Biology, National Cancer Institute, Bethesda, MD, USA.
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  • Gisela Storz

    Corresponding author
    1. Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA.
      E-mail storz@helix.nih.gov; Tel. (+1) 301 4020968; Fax (+1) 301 4020078.
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E-mail storz@helix.nih.gov; Tel. (+1) 301 4020968; Fax (+1) 301 4020078.

Summary

In bacteria, many small regulatory RNAs (sRNAs) are induced in response to specific environmental signals or stresses and act by base-pairing with mRNA targets to affect protein translation or mRNA stability. In Escherichia coli, the gene for the sRNA IS061/IsrA, here renamed McaS, was predicted to reside in an intergenic region between abgR, encoding a transcription regulator and ydaL, encoding a small MutS-related protein. We show that McaS is a ∼ 95 nt transcript whose expression increases over growth, peaking in early-to-mid stationary phase, or when glucose is limiting. McaS uses three discrete single-stranded regions to regulate mRNA targets involved in various aspects of biofilm formation. McaS represses csgD, the transcription regulator of curli biogenesis and activates flhD, the master transcription regulator of flagella synthesis leading to increased motility, a process not previously reported to be regulated by sRNAs. McaS also regulates pgaA, a porin required for the export of the polysaccharide poly β-1,6-N-acetyl-d-glucosamine. Consequently, high levels of McaS result in increased biofilm formation while a strain lacking mcaS shows reduced biofilm formation. Based on our observations, we propose that, in response to limited nutrient availability, increasing levels of McaS modulate steps in the progression to a sessile lifestyle.

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