Figure 8. Model for serial transfer of SitA.
(A) SitA is delivered cell-to-cell by OME. After OME, SitA may enter the cytoplasm or linger (lag) in the OM. (B) In the delayed entry model, the infected cell can undergo OME of SitA to another naïve cell before all SitA molecules enter the cytoplasm and before cell death. n = number of target cells poisoned by infected cell. (C) Alternative, but non-exclusive model in which OME and SitA transfer occurs between three or more cells simultaneously. Here SitA is delivered to a tertiary cell via an intermediary cell.