Abstract
The basal structure of the flagellum controls both activity and assembly. In order to define the steps involved in these processes, genetic analysis was performed. Twenty genes were found to be required for the complete assembly and function of the organelle. FlaE controls the length of the hook, flaA is required both to maintain flagellar structure and for chemotaxis, and flaI plays a role in regulating the synthesis of the entire structure. Mutations mapping close to flal (the cfs mutations) release flagellar synthesis from control by catabolite repression.
The basal structure was purified and isolated. On SDS acrylamide gel electrophoresis, it contained at least six distinguishable components. One major band corresponded to the hook subunit with an apparent molecular weight of 42,000 daltons. The others had apparent molecular weights of 60,000, 40,000, 28,000, 25,000, and 18,000 daltons. The genes that correspond to these polypeptides have not been identified.
In exploring the role of the mot and che genes, assays were developed for the function of individual flagellar filaments. The filaments were found to rotate and rotation could be modulated by changing their direction. Chemotaxis results from the modulation of flagellar rotation. Using the rotation assay the response of nonmotile cells to attractants and repellents was followed.