Structure of bacterial flagella from Salmonella typhimurium: Effects of hydration and some stains on the equatorial X-ray diffraction patterns of cast films

Abstract

Both the low- and high-angle X-ray diffraction patterns of detached flagella in the form of cast films have been examined at various conditions of specimen relative humidity from 100 to 0% both without staining and following staining with uranyl acetate, phosphotungstic acid, mercuric chloride and osmium tetroxide. The packing of the very short flagella fragments in the preparations was found to be a function of the mean flagellum length. The resulting low-angle equatorial reflexions are explained on the basis of a lattice showing Boltzmann separation statistics; the effects of the flagellar packing do not extend to the high-angle patterns. The stains differ considerably in their effects. For example, uranyl acetate preserves best both the low- and high-angle X-ray patterns although the Fourier transform of a single flagellum is altered. Phosphotungstate produces swelling of the short flagella and these experiments show clearly that the flagella have a core which can be penetrated by stain but give no detailed information on its nature; following phosphotungstate staining, the high-angle X-ray diagram is amorphous. The relationship between these results and those of electron microscopy is discussed. The experiments show that the flagellum diameter is close to 140 Å and is little affected by drying. As drying proceeds, progressive changes occur in the equatorial diffraction pattern. The results proved disappointing of Fourier inversion of some of the continuous low-angle equatorial diffraction patterns.