Additional structures associated with bacterial flagellar basal body.

By fixation of preparations prior to negative staining, we have been able to visualize additional features attached to the basal body of Salmonella typhimurium. These new features consist of arms attached to the M ring, a cap resting atop the arms, and a dome attached to the rod. These structures may be parts of the motor and/or of the putative, flagellar export apparatus. Preparations from mutant strains show that the presence of these features does not depend on the presence of the motA, motB or cheA genes.