Figure 10. Model for spoIVB2 regulation by the C. difficile SASPs.

In a working model for how C. difficile SASPs regulate sporulation, we hypothesize that upon σ^G activation in the forespore of wildtype C. difficile cells, SspA and SspB become expressed, and they bind to spoIVB2 to prevent prolonged accumulation of SpoIVB2. In the C. difficile ΔsspA ΔsspB or in the C. difficile ΔsspB^* strains, the SASPs do not accumulate and SpoIVB2 retains prolonged activity in the forespore compartment. In the C. difficile ΔsspA ΔsspB or in the C. difficile ΔsspB^* suppressor strains, the SpoIVB2^A20T or the spoIVB2_F37F alleles lead to lower amounts of SpoIVB2 activity (either through changes in protease activity or due to translational changes, respectively) later in sporulation. Created with BioRender.com.