Incomplete flagellar structures in nonflagellate mutants of Salmonella typhimurium

Abstract

Incomplete flagellar structures were detected in osmotically shocked cells or membrane-associated fraction of many nonflagellate mutants of Salmonella typhimurium by electron microscopy. The predominant types of these structures in the mutants were cistron specific. The incomplete basal bodies were detected in flaFI, flaFIV, flaFVIII, and flaFIX mutants, the structure homologous to a basal body in flaFV mutants, the polyhook-basal body complex in flaR mutants, and the hook-basal body complex in flaL and flaU mutants. No structures homologous to flagellar bases or their parts were detected in the early-fla group nonflagellate mutants of flaAI, flaAII, flaAIII, flaB, flaC, flaD, flaE, flaFII, flaFIII, flaFVI, flaFVII, flaFX, flaK, and flaM. From these observations, a process of flagellar morphogenesis was postulated. The functions of the early-fla group are essential to the formation of S ring-M ring-rod complexes bound to the membrane. The completion of basal bodies requires succeeding functions of flaFI, flaFIV, flaFVIII, and flaFIX. Next, the formation of hooks attached to basal bodies proceeds by the function of flaFV and by flaR, which controls the hook length. Flagellar filaments appear at the tips of hooks because of the functions of flaL, flaU, and flagellin genes.

Roles of partly unfolded conformations in macromolecular self‐assembly

“…The assembly process starts from the FliF ring (also called the MS ring) complex in the cytoplasmic membrane, and proceeds in both inward and outward directions, as well as laterally (Suzuki et al 1978;Suzuki & Komeda 1981;Jones & Macnab 1990;Kubori et al 1992Kubori et al , 1997. The inward assembly involves the The end-on view shows the shape of the subunit and 11 protofilaments forming the tubular structure.…”

Constraints on models for the flagellar rotary motor

“…The motor is built from the inside out (for a short review, see Aizawa 1996). This was recognized by Suzuki et al (1978), who studied mutants of Salmonella defective for di¡erent £a genes (now called £h, £i and £g; see Iino et al 1988) and searched in pellets obtained from detergent extracts for incomplete £agellar structures. The simplest structure found was a`rivet', comprising the MS-ring and rod.…”

Bacterial flagellation and cell division

“…Historically, the pathway of flagellar morphogenesis was first revealed by analysing incomplete flagellar structures by electron microscopy on the membrane-associated fractions and osmotically shocked cells of nonflagellate mutants (Suzuki et al 1978;Kubori et al 1992). An intermediate structure as small as the MS ring complex can be seen, and the alignment of those structures in the order of size leads us to a construction pathway of a whole flagella.…”

“…Based on the observations described above, we assume that the formation of a hook-basal body (HBB) complex takes two generations at any phase of growth, and that both the mature and immature flagella are divided equally between the two daughter cells. During the construction of HBB complexes, there are several kinds of precursors: the MS ring complex, the rivet-like structure, candle stick and so on (Suzuki et al 1978). For simplicity, let F 0 represent the precursors of HBB undetectable by EM and F 1 the half-mature and detectable precursors.…”