Genetics and Assembly

Abstract

Some 50 genes encode products necessary for the assembly and operation of the chemotaxis system. These are shown on the genetic map of E. coli in Fig. 10.1. Arrows indicate operon structure, as described in the figure legend. Most of these genes specify components required for construction of the flagellar rotary motor. They fall into three hierarchical sets (Table 10.1). The early set specifies the transcriptional regulators, FlhD and FlhC., required for expression of all the other genes. The middle set encodes components of the hook-basal body, including the transport apparatus, rotor, drive shaft, bushing, hook, hook-associated proteins, and filament cap; recall Fig. 9.3. It also encodes a protein (FliA, alias σ^F or σ²⁸) destined to turn on the late genes, together with a protein, FlgM, that inactivates it. The regulatory proteins are listed in Table A.4 in the appendix. FlgM is pumped out of the cell by the transport apparatus when the hook-basal body is complete (Hughes et al., 1993; Kutsukake, 1994). This allows expression of genes that encode the filament (FliC), the force generators (MotA, MotB), and everything else required for direction control (receptors and che-gene products).