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Team:Paris Bettencourt/SinOp
From 2011.igem.org
The Bacillus subtilis sin operon
Introduction
The sin operon of bacillus subtilis can be tuned in a bistable switch [1]. This cellular systems has evolved to deal with short-term adaptation to environmental fluctuation by implementation of the appropriate stress responses. Sin operon is involved in many stress situation, such as biofilm formation, sporulation, etc.
This operon is under control of the repressor SinR. Derepression is mediated by the antirepressor SinI, which binds to SinR with a 1:1 stoichiometry.
Biofilm formation and sporulation are also connected in that both processes are dependent on Spo0A, the master regulator for entry into sporulation [2].
Sporulation
Sporulation is a dramatic response to stress and is a particularly expensive endeavor for the cell, in terms of both time and materials. The exact conditions and timing for sporulation are likely to be under strong selective pressure as both premature and belated spore production can have disastrous effects on cell growth and survival. Thus, an intricate phosphorelay and a transcriptional regulatory network carefully control the onset of sporulation .The sin operon is central to the timing and early dynamics of this network.
Sporulation can be triggered with high efficiency in cells in the exponential phase of growth in rich medium by artificial induction of the synthesis of KinA, a kinase protein which phosphorylates Spo0AP. The accumulation of Spo0AP induces the expression of SinI, which binds to and inactivates SinR. The combined effect of positive regulation by Spo0AP and the inactivation of the negative regulator SinR activates the sporulation pathway. SpoIIA gene is early express in this situation.
Biofilm formation
Biofilms of Bacillus subtilis consist of long chains of cells that are held together in bundles by an extracellular matrix of exopolysaccharide The exopolysaccharide is produced by enzymes encoded by the epsA-O operon operons are under the control of the repressor SinR. Derepression is mediated by the antirepressor SinI.
In B.subtilis, the matrix consists of an exopolysaccharide, which is produced under the direction of the 15-gene operon epsA-O.
References
- Voigt, Christopher Wolf, Denise Arkin, Adam P 2005
- Sonenshein, 2000; Branda et al., 2001; Hamon and Lazazzera, 2001
