Current concepts of the morphology and biology of Treponema pallidum based on electron microscopy.

Abstract

The development of electron microscopy has advanced our knowledge of the morphology of Treponema pallidum, but the exact significance of some of the formations observed is not yet clear and requires further detailed study by chemists as well as morphologists. The literature has been reviewed and our methods described in previous reports (Ovcinnikov and Delektorskij, 1968, 1969, 1970a. In this paper we shall limit ourselves to a description of our most recent results.The classic spiral shape of T. pallidum, with coils of regular width and depth slightly narrower towards the acuminate ends, is to be considered as typical for this organism.We shall not reproduce here the illustrations already published in various periodicals; the photographs illustrating the present study have not previously been published.Examination of preparations processed by the negative contrast method with a magnification X6-8000 has confirmed the fact that the thickness of the treponeme is uneven along its length, as established previously in light microscopic studies on living specimens. It has been proved that the thickness changes as the treponeme moves; this clearly shows that the body of T. pallidum is able to contract and, consequently, has a special apparatus for this purpose.With greater magnification it can be seen that in young cultures the body of the treponeme is covered by a transparent mass forming a wide mucoid sheath (Ovcinnikov and Delektorskij, 1969). In older cultures this sheath cannot be demonstrated, and the question of its origin (i.e. whether it is a product of the treponeme or derives from the host tissues) should be studied in relation to the specific localization of the organism and the conditions of its existence.Bearing in mind certain differences in the structure of cultivated and pathogenic treponemes, we shall

Persisting atypical and cystic forms of Borrelia burgdorferi and local inflammation in Lyme neuroborreliosis

“…Reconversion of cystic Borrelia burgdorferi into the typical spiral form has been demonstrated in vitro and in vivo [8,10,31,40]. …”

Effect of hyperbaric oxygen on experimental syphilis in the rabbit.

“…It might be supposed with considerable probability that hyperbaric oxygen produces unfavourable conditions for the existence of T. pallidum in spiral form, but it retains its virulence and germinative ability in some other more resistant form, which after cessation of the harmful influence of hyperbaric oxygenation, again develops an abundant growth of spiral forms. Such ability of treponemes to produce non-spiral forms under adverse circumstances under the action of penicillin has recently been described in electron microscopic studies (Ovcinnikov and Delektorskij, 1971), and it may be assumed that HBO is a stressful factor having a similar influence on treponemes in vivo.…”

Ultrastructural Studies of Treponemes: Location of Axial Filaments and Some Dimensions of Treponema pallidum (Nichols strain), Treponema denticola , and Treponema reiteri

“…The electron micrographs of cells from a syphilitic chancre, published by Azar et al (1), showed that the axial filaments of T. pallidum were external to the body of the 100 on August 1, 2020 by guest http://iai.asm.org/ Downloaded from ULTRASTRUCTURAL STUDIES OF TREPONEMES organisms and failed to reveal any outer trilaminar structure. The electron microscopy observations of Hasegawa (3) also showed the external location of the filaments despite the fact that he postulated a thin outer membrane, as described by Ocvinnikov and Delektorskij (9). Hasegawa (3) also considered that "it is also very difficult to differentiate these spirochaetes (T. pallidum) from those of the nonvirulent Reiter strain."…”

“…However, in a close scrutiny of the electron micrograph upon which this conclusion was based, it appears that the apparent cell membrane is in reality adjacent cell debris. Ovcinnikov and Delektorskij (9) categorically state that in T. pallidum the outer wall consists of "two electron-dense layers and one electron-transparent layer. The cytoplasmic membrane also has three layers.…”

“…Such findings suggested the concept that T. pallidum might be morphologically different from some of the nonpathogenic treponemes in having the axial filaments external to the body of the organism and not surrounded by a trilaminar structure, such as that demonstrated in the case of T. reiteri (10) and T. denticola (6,7). In addition to these contrasting views on the location of the axial filaments of T. pallidum (Nichols), there also is a marked lack of agreement on the size of this organism (2,3,5,8,9,12,13). The present study was designed to resolve these differences and to compare the ultrastructural morphology of virulent T. pallidum (Nichols) with two representative nonpathogenic treponemes, T. reiteri and T. denticola (microdentium).…”