File Name : suppfigure1_liebal.tif Caption : Supplement Figure 1: Repeated addition of IPTG to ensure steady activation of SigmaB expression and thus steady transcription of lacZ. File Name : suppfigure2_liebal.tif Caption : Supplement Figure 2: Model for testing a SigmaB independent activation of the protease. The variable Sgn is an external signal for the expression of protease X. The network diagram is translated to a set of differential equations and then fitted to the experimental data. File Name : suppfigure3_liebal.tif Caption : Supplement Figure 3: IPTG-induced beta-galactosidase expression from a SigmaB-dependent ctc::lacZ fusion in a clpP knock-out strain. File Name : suppfigure4_liebal.tif Caption : Supplementary Figure 4: Absolute parameter correlation for the 'transcription inhibition' (A), 'SigmaB proteolysis' (B) and 'prost-transcriptional instability' (C) models.