Figure 3. The observed σ^V heterogeneity can be explained by a simplified σ^V circuit.

• A
  Schematic of the σ^V circuit. In the figure, R (orange) is the anti‐sigma factor RsiV, R* (orange) is RsiV bound to lysozyme, S (red) is signalling peptidase, RP (light blue) is RasP the site‐2 protease, O (blue) is OatA, and Y (grey) is YrhK. For more information on the activation mechanism, see Fig 1B.
• B, C
  RNA‐seq experiment on WT (JLB130) and ΔsigV (JLB154) strains, showing quantification of the absolute expression of individual genes in the presence and absence of lysozyme stress. The shaded grey box represents a ± 5 fold change. DEseq was used to identify genes which were differentially expressed with a 5% P‐value cut‐off between the WT and ΔsigV mutant in response to lysozyme treatment (default DEseq test was used). (B) Only the sigV operon is strongly activated (> 5 fold change) in response to lysozyme stress in WT (JLB130), as previously reported (Guariglia‐Oropeza & Helmann, 2011). (C) No genes were strongly upregulated in ΔsigV (JLB154) by lysozyme stress.
• D
  Effect of the overexpression of individual components of the σ^V pathway (Biological repeats: WT: n = 8, sigV ⁺: n = 4, rsiV ⁺: n = 3 oatA ⁺: n = 4, yrhK ⁺: n = 3, sipS ⁺: n = 3 and rasP ⁺: n = 3, pbpX ⁺: n = 6) on the fraction of activated cells. Only overexpression of sigV, rsiV or oatA changed the observed dynamics compared to WT. The histograms of the shown data are shown in Appendix Fig S16.
• E
  Deleting oatA did not alter the σ^V activation dynamics. However, deleting sigV or rsiV resulted in no further activation of σ^V in response to 1 ug/ml lysozyme. n ≥ 3 biological repeats for all data shown. The histograms of the shown data are shown in Appendix Fig S17.
• F
  Schematic of simplified σ^V circuit with only σ^V and RsiV, where σ^V (green) activates its own expression and that of its anti‐sigma RsiV (orange, R).

Data information: Bars correspond to the mean ± s.d. For more information on the number of repeats, please see Appendix Table S3.