Structure of complex flagellar filaments in Rhizobium meliloti

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Abstract
The complex flagella of R. meliloti 2011 and MVII-1 were analyzed with regard to serology, fine structure, subunits, and amino acid composition. The serological identities of flagellar filaments of the 2 strains were demonstrated by double immunodiffusion with antiflagellin antiserum. The filaments had a diameter of 16 nm. Their morphology was dominated by the prominent undulations of an external 3-start helix running at a 10-nm axial distance and at an angle of 32.degree.. Faint nearly axial striations indicated the presence of a tubular core of a different helical order. The complex filaments consisted of 40,000-dalton flagellin monomers. The amino acid composition was 3-4% higher in nonpolar residues and 5-7% lower in aspartic and glutamic acids (and their amides) than that of plain flagellar proteins. There were no immunochemical relationships among P. rhodos, R. lupini, and R. meliloti complex flagella, suggesting that the latter represent a new class.