Expression of cell polarity during Caulobacter differentiation

The bacterium Caulobacter crescentus generates two distinct progeny cells, a motile swarmer cell and a sessile stalked cell, at every cell division. The dramatic morphological and physiological differences between the progeny are expressed in the predivisional cell prior to separation. We review recent work examining mechanisms responsible for differentiation of the incipient swarmer and stalked cell compartments. These include differential transcription of the newly replicated chromosomes, and targeting of proteins to specific poles. The biosynthesis of the polar flagellum is emphasized as a model for studying these processes. Hypotheses concerning the role of the cell poles in expression of asymmetry are discussed.