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: Contribution to journalArticle

32 Scopus citations

Abstract

Exponentially growing Bacillus subtilis cultures are epigenetically differentiated into two subpopulations in which cells are either ON or OFF for σ d-dependent gene expression: a pattern suggestive of bistability. The gene encoding σ D, sigD, is part of the 31-gene fla/che operon where its location at the 3' end, 25kb away from the strong P fla/che promoter, determines its expression level relative to a threshold. Here we show that addition of a single extra copy of the slrA gene in the chromosome inhibited σ d-dependent gene expression. SlrA together with SinR and SlrR reduced sigD transcript by potentiating a distance-dependent decrease in fla/che operon transcript abundance that was not mediated by changes in expression from the P fla/che promoter. Consistent with acting upstream of σ D, SlrA/SinR/SlrR was bypassed by artificial ectopic expression of sigD and hysteretically maintained for 20 generations by engaging the sigD gene at the native locus. SlrA/SinR/SlrR was also bypassed by increasing fla/che transcription and resulted in a hypersensitive output in flagellin expression. Thus, flagellin gene expression demonstrated hypersensitivity and hysteresis and we conclude that σ d-dependent gene expression is bistable.

Original languageEnglish (US)
Pages (from-to)1210-1228
Number of pages19
JournalMolecular Microbiology
Volume83
Issue number6
DOIs
StatePublished - Mar 1 2012

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