This Caulobacter crescentus cell has completely separated its inner membrane and cell wall, but not yet the outer membrane and surface layer.
In some species, the outer membrane constricts at the same time as the inner membrane, as you saw, for instance, in the Thiomonas intermedia cell at the beginning of this chapter. In others, including the cells you saw on the last page, the outer membrane is mainly remodeled at the end of the process, as the cells separate. Other species are intermediate. In Caulobacter crescentus, the outer membrane constricts along with the inner membrane and cell wall. At the end of division, though, the inner membrane seals off before the outer membrane, as you can see in this cell, which is at a very late stage of division. For an even later stage, see the example in the Learn More section (⇩).
This Caulobacter crescentus cell has completely separated its inner membrane and cell wall, but not yet the outer membrane and surface layer.