(a) Morphological effect of overexpression and depletion of CtpS. Shown are phase images of wild type Caulobacter (left), and Caulobacter overexpressing (middle) or depleted (right) for CtpS. Above panels b–j is a cartoon representation of the synthetase and GAT domains of Caulobacter CtpS (not to scale). (b–d) Localization of wild-type and mCherry-CtpS point mutants. Merged phase-fluorescence (top) and fluorescence (bottom) images of cells expressing wild-type mCherry-CtpS (b, ZG153), synthetase domain mutant (c, ZG154), and GAT domain mutant (d, ZG155). (e–j) Effects of overexpression of wild-type CtpS (e, ZG208) and (h, ZG212), the synthetase mutant (f, ZG209) and (i, ZG213), and the GAT mutant (g, ZG210) and (j, ZG214) on cell shape (e–g) and CreS-tc localization (h–j). The arrow in (i) points to faint residual CreS-tc localization along the side of the cell. Scale bars are 2 μm.