Shape of Bacterial Flagella

Abstract

IN orthodox bacteriology all flagella are curly. With the exception, however, of spirilla, which possess unchanging horny-looking curly appendages (Fig. 1) directly derived from the cell wall¹, motile bacteria usually go forward with a fuzzy-looking straight tail (Fig. 2) and a twisting body². Under various, probably adverse, conditions this straight tail tends to stiffen into a straight clear-cut rod but more often into a clear-cut helix³. The straight tail of Fig. 3 actually became the helix of Fig. 4, and the helix of Fig. 5 also arose from a straight tail. The helices may show two different but characteristic wave-lengths in the same bacterium, one always exactly twice the other as in Figs. 4 and 5, for which phenomenon ‘biplicity’ would appear a suitable term³.