Electron microscopy of flagellation in species of Spirillum.

Migula, in 1900, separated the genus Spirillum Ehrenberg from the other spiral bacteria on the basis of motility by means of tufts of polar flagella. Mligula mentioned the fact that the tuft, in certain species, was often agglutinated into a fascicle which appeared as a single flagellum in flagellar stain preparations. Tufts of polar flagella long remained a generally accepted distinguishing morphological character of the genus. This character was not, however, always observed by all investigators. For example, Beijerinck (1925) and Dimitroff (1926) described species of Spirillum as having a single flagellum. Giesberger (1936) was the first investigator of the genus Spirillum to insist on a rigid interpretation of the character of tufts of polar flagella. He suggested that those species which had been described as having a single flagellum be transferred to the genus Vibrio. Williams and Rittenberg (1957) described six species of the genus Spirillumn as having a single flagellum in flagellar stain preparations prepared after the manner of Gray (1926). In their discussion of flagellation these authors admitted that the single flagellum might be a fascicle such as had been mentioned and illustrated by AMigula (1900). They justified their description of the six species as having a single flagellum on the fact that only a single flagellum could be seen in living cells of the larger species when the cells were observed by phase contrast. In such phase contrast observations of living cells the flagellum appeared as a whiplike organelle without that fuzziness in the outline which would have been apparent if a number of flagella were being moved in unison. This electron microscopic survey had two