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SlrA/SinR/SlrR inhibits motility gene expression upstream of a hypersensitive and hysteretic switch at the level of σ D in Bacillus subtilis
Author(s) -
Cozy Loralyn M.,
Phillips Andrew M.,
Calvo Rebecca A.,
Bate Ashley R.,
Hsueh YiHuang,
Bonneau Richard,
Eichenberger Patrick,
Kearns Daniel B.
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.08003.x
Subject(s) - biology , flagellin , operon , gene , gene expression , subcloning , microbiology and biotechnology , bacillus subtilis , transcription (linguistics) , lac operon , genetics , regulation of gene expression , ectopic expression , plasmid , escherichia coli , bacteria , linguistics , philosophy
Summary 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, 25 kb 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.