Regulation of Flagellum Biosynthesis and Motility inCaulobacter

Abstract

This chapter describes the molecular events that lead to the biogenesis of the Caulobacter crescentus flagellum and how these events are integrated into the generation of a new daughter cell type. Flagellar biogenesis is the best-known aspect of cellular differentiation in C. crescentus. The C. crescentus flagellum has been observed by electron microscopy and possesses a structure that is typical of flagella from gram-negative bacteria. Growth of the newly divided or differentiated stalked cell is accompanied by the formation of a swarmer cell at the pole opposite the stalk. Flagellar biogenesis in the stalked and predivisional cell is regulated by both cell cycle and flagellar assembly events. The molecular dissection of the cell cycle events resulting in the timed expression of flagellar genes has yielded important information about how bacteria utilize the cell cycle to regulate gene expression. A hallmark of the C. crescentus developmental program is the asymmetric positioning of proteins in the predivisional cell. The most likely candidate for the regulator of compartmentalized transcription is the transcriptional activator, FlbD. The cellular distribution of FliF was found to parallel that of methyl-accepting chemotaxis receptor (MCP). The FliF that is present in swarmer cells is degraded upon differentiation into a stalked cell.