[17] Genetics of Caulobacter crescentus

This chapter discusses the genetics of Caulobacter crescentus. Caulobacter crescentus is a gram-negative, aquatic bacterium, characterized by an unusual cell cycle. The stalked cell immediately begins to replicate its chromosome and prepare for the next ceil division. Midway through chromosome replication, differentiation begins at the pole opposite the stalk, resulting in the synthesis of a flagellum, pill, and membrane phage receptors. This differentiated pole confers motility on the progeny swarmer cell when cell division occurs. Caulobacter crescentus lives in ponds and streams and is a scavenger in nature. It is adapted to growth in low nutrient conditions and grows poorly, if at all, in media designed for Escherichia coli. Many kinds of C. crescentus mutants can be obtained without mutagenesis. Antibiotic-resistant mutants can be obtained by direct selection, and motility mutants can be obtained by serial enrichment procedures for nonmotile cells on soft afar plates. Auxotrophic mutants can be obtained after enrichment for nongrowing cells.