We followed the distribution of MurG-YFP in single cells early in sporulation, taking images every 5 min for 1 h starting at T3 (Fig. 1A). At the beginning of the time-lapse experiment YFP signal from the MurG-YFP fusion was homogeneously distributed around the mother cell cytoplasm, but over time MurG-YFP accumulated progressively at the forespore as indicated by the co-stained FM4- 64 images (Fig. 1A). Although MurG does not have any obvious transmembrane domains, when the movie ended at T4, MurG-YFP had clearly redistributed and was contiguous around the forespore membrane. The ratio of fluorescence across the forespore to the fluorescence across the mother cell also reflects the re-distribution of MurG-YFP as it changed from 1 at T3 to 2.5 at T4 (Fig. 1B and D).