Fig 8. Model illustrating the relationship of SsdC with the spore coat and cortex.

Schematic representation of SsdC localization and its relationship to the spore cortex and coat. The green arrow represents the localization relationship between SsdC and the coat, and the red arrow represents the shape relationship between SsdC and the cortex. We hypothesize that SsdC influences the assembly of the cortex through the spore coat and may act to coordinate the assembly of these two spore envelope layers. In this model, SafA crosses the spore outer membrane. Although recent data suggests that SafA can interact with cortex peptidoglycan in mature spores and efficient localization of SafA depends on cortex synthesis [56], it remains unclear if SafA actually transverses the membrane to do so, or if the forespore outer membrane becomes permeable, or disappears, as the spores mature.