SlrA/SinR/SlrR inhibits motility gene expression upstream of a hypersensitive and hysteretic switch at the level of σ(D) in Bacillus subtilis.

Loralyn M. Cozy, Andrew M. Phillips, Rebecca A. Calvo, Ashley R. Bate, Yi Huang Hsueh, Richard Bonneau, Patrick Eichenberger, Daniel B. Kearns

Research output: Journal ArticleArticlepeer-review


<div class="line" id="line-15"> Exponentially growing <i> Bacillus subtilis </i> cultures are epigenetically differentiated into two subpopulations in which cells are either ON or OFF for &sigma;d&hyphen;dependent gene expression: a pattern suggestive of bistability. The gene encoding &sigma;D, <i> sigD </i> , is part of the 31&hyphen;gene <i> fla/che </i> operon where its location at the 3&prime; end, 25&emsp;kb away from the strong <i> Pfla/che </i> promoter, determines its expression level relative to a threshold. Here we show that addition of a single extra copy of the <i> slrA </i> gene in the chromosome inhibited &sigma;d&hyphen;dependent gene expression. SlrA together with SinR and SlrR reduced <i> sigD </i> transcript by potentiating a distance&hyphen;dependent decrease in <i> fla/che </i> operon transcript abundance that was not mediated by changes in expression from the <i> Pfla/che </i> promoter. Consistent with acting upstream of &sigma;D, SlrA/SinR/SlrR was bypassed by artificial ectopic expression of <i> sigD </i> and hysteretically maintained for 20 generations by engaging the <i> sigD </i> gene at the native locus. SlrA/SinR/SlrR was also bypassed by increasing <i> fla/che </i> transcription and resulted in a hypersensitive output in flagellin expression. Thus, flagellin gene expression demonstrated hypersensitivity and hysteresis and we conclude that &sigma;d&hyphen;dependent gene expression is bistable.</div>
Original languageAmerican English
JournalMolecular Microbiology
StatePublished - Jan 3 2012
Externally publishedYes


  • Genetics
  • Biology
  • Molecular Biology

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