Figure 1.

(a) Brucella spp., like other Rhizobiales, exhibit unipolar growth from the new cell pole. As the cell cycle progresses, cell growth shifts from being exclusively polar to being at both the pole and the nascent division site (growth sites colored orange). The Brucella developmental regulators, PdhS and DivK, exhibit dynamic polar localization to the inner membrane as a function of cell cycle. The new (N) pole and old (O) cell pole are marked. (b) Model of the CckA-ChpT-CtrA phosphorelay. The histidine kinase CckA autophosphorylates on a conserved histidine residue and transfers a phosphoryl group to a conserved aspartic acid residue on its C-terminal receiver domain. CckA~P transfers a phosphoryl group to the ChpT phosphotransferase, which can subsequently transfer this phosphoryl group to the receiver domain of CtrA. CtrA~P is a DNA-binding response regulator that modulates transcription of genes controlling cell polarity, division, and intracellular survival.