Morphologic characteristics of certain cultured strains of
oral spirochetes and Treponema pallidum
as revealed by the electron microscope.

Hampp EG, Scott DB, Wyckoff RWG
J Bacteriol 1948;56:755-69
48_02 Morphologic char spirochet & TP EM.tif [Imaging for W95B+]

Shadowed preparations of pure cultures of two strains of the small oral treponemes, four strains of Borrelia vincentii, and the Nichols and Noguchi cultured strains of Treponema pallidum have been studied with the electron microscope. Morphological characteristics, filamentous and flagellar appendages, and granules of various types have been described and illustrated.

Excerpt:
Typical free granules, the end products of granule 'shedding', are shown in figure 18.
They are roughly circular in outline and sharply bounded. They consist for the most part of what appear to be short sections of spirochetes closely packed together. The contents of these granules are probably responsible for the fine lacelike appearance and the bright white, highly refractile bodies described by Hampp (1946) under the dark-field microscope.
Examples of another type of free granule repeatedly observed are shown in figures 19 and 20. These granules consist of tangled masses of spirochetes or spirochetal segments.
The significance of granules in the life history of the spirochetes is unknown but certain investigators have suggested that they may be germinative units (Balfour, 1911; Noguchi, 1911; Noguchi, 1917; Leishman, 1918; Mudd et al., 1943; Hampp, 1946). Others are undecided or hesitant in accepting this hypothesis (Fantham, 1916; Akatsu, 1917; Wenyon, 1926; Warthin and Olsen, 1930). Topley and Wilson (1936) have indicated that they are probably particles of culture medium adhering to the sides of the spirochetes. The electron micrographs demonstrate that this explanation is wrong, and that free granules are definitely a phase in the development of spirochetes. Although it is not possible to determine from these micrographs that the granules are germinative units their constant rhythmic occurrence in living cultures suggests this possibility. Further support of this hypothesis is provided by the fact that cultures up to 31 months old, showing only refractile granules by dark-field examination have invariably given normal growths on transfer to fresh medium (Hampp, 1946)