Brit. J. vener. Dis. (1971) 47, 315 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
Current concepts of the morphology and biology of Treponema pallidum based on electron microscopy
N. M. OVCINNIKOV AND V. V. DELEKTORSKIJ Department of Microbiology, Central Research Institute of Skin and Venereal Diseases (Director: Prof. N. M. Turanov), Ministry of Health, Moscow, USSR
The development of electron microscopy has ad- describe first the cultivated strains and then the vanced our knowledge of the morphology of Trepo- pathogenic organism. A comparative study of several nema pallidum, but the exact significance of some of cultivated strains (Reiter, Kazan, and Stavropol) the formations observed is not yet clear and requires has already revealed certain variations, but they are further detailed study by chemists as well as morpho- not very significant. One end of the treponeme logists. The literature has been reviewed and our carries an oval formation which we have named methods described in previous reports (Ovcinnikov 'head structure' (Ovcinnikov and Delektorskij, 1968, and Delektorskij, 1968, 1969, 1970a). In this paper 1969). Its shape is somewhat variable and it contains we shall limit ourselves to a description of our most basal granules, which are the sites of attachment of recent results. the fibrils and are possibly the centres controlling The classic spiral shape of T. pallidum, with coils of movement. When living treponemes are examined regular width and depth slightly narrower towards by darkfield microscopy this structure may exhibit ancopyright. the acuminate ends, is to be considered as typical abrupt rotatory motion. The opposite end is usually for this organism. devoid of such a formation. We shall not reproduce here the illustrations During certain periods of growth, probably before already published in various periodicals; the photo- the division of the treponeme, the head structure is graphs illustrating the present study have not pre- shed together with the fibrils. This head structure is viously been published. plainly visible in cultivated strains, but we could not Examination of preparations processed by the clearly discem it in the pathogenic T. pallidum. http://sti.bmj.com/ negative contrast method with a magnification X6-8000 has confirmed the fact that the thickness The basal granules have an annular shape (Fig. 1); of the treponeme is uneven along its length, as the fibrils that are attached to them stretch towards in microscopic studies the opposite end of the treponeme encircling its body. established previously light the view that are on living specimens. It has been proved that the We do not agree with these fibrils thickness changes as the treponeme moves; this inserted in the ends of the treponeme or in one end only, remaining free at the opposite end. Actually, clearly shows that the body of T. pallidum is able on September 27, 2021 by guest. Protected to contract and, consequently, has a special apparatus each fibril has two insertions: one into a basal for this purpose. granule at one end of the treponeme and the other seen that in into some other part of its body. The number of With greater magnification it can be between young cultures the body of the treponeme is covered fibrils differs not only individual specimens the of a in the by a transparent mass forming a wide mucoid but throughout body single treponeme; In middle of the body one may find ten to twelve fibrils sheath (Ovcinnikov and Delektorskij, 1969). older and this sheath cannot be demonstrated, and the but in another part only three, so on. cultures are studied the question of its origin (i.e. whether it is a product of When the organisms by negative or derives from the host contrast method the fibrils appear to lie on the surface the treponeme tissues) seem to be should be studied in relation to the specific locali- of the treponeme and sometimes entirely zation of the organism and the conditions of its free. This impression prompted some authors to existence. suggest that T. pallidum lacks flagella. Bearing in mind certain differences in the structure Mesosomes, rounded formations of various sizes, of cultivated and pathogenic treponemes, we shall are distributed throughout the body of the tre- poneme. They probably differ in their structure and Received for publication March 1971 functions, and are called mesosomes only because Paper presented at the International Colloquium on the Late Trepo- nematoses, Miami, Florida, U.S.A., on January 4-8, 1971 they cannot yet be further indentified. 316 British Journal of Venereal Diseases Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
The treponeme has a granular surface, and delicate ('spheroids', according to their terminology) and the parallel bands course along its body. encystment of treponemes under unfavourable In pathogenic treponemes (Nichols, I, Budapest conditions, reached the unexpected conclusion that strains) studied by the negative contrast method, the the cysts were a product of degeneration and not a terminal formations at the two opposite ends differ means of safeguarding the existence of the organism. radically in structure. One end of the organism is As a proof, they mention the fact that 'spheroids' are acuminate and consists of tubular formations con- formed under the influence of diverse stressful tained in a round cavity, but the other end is devoid of factors. In our opinion, this fact affirms rather than them. denies the assumption that the encystment of tre- Each end is provided with a spongy mass adjacent ponemes is a protective mechanism ensuring survival to the outer wall and with basal granules carrying in adverse circumstances. fibrils. If the stress causing encystment surpasses the ad- In past years opinions have differed as to the mode aptive capabilities of the treponeme, the organism of reproduction of T. pallidum. It has now been perishes and then undergoes degeneration. If the proved beyond any doubt that transverse fission is stress is not lethal, accessory envelopes are formed the main mode of reproduction. The treponeme and the treponemes become well encapsulated and divides into halves or undergoes multiple division. may survive new stresses many times stronger than The new organisms may be so numerous that some the initial one. Encystment as a mechanism of of them measure hardly more than one coil of the survival and mode of reproduction is widespread in original. This fact is very important, both from the nature, especially among protozoa. purely morphological point of view, and because it Under stressful conditions, the treponeme 'packs' testifies to the possible existence of non-spiraJ forms itself into a compact roll (Fig. 8) and becomes
of T. pallidum. During the process of division into covered with a transparent mucoid capsule, which copyright. halves, an isthmus is formed; old fibrils are shed and resists the penetration of drugs and antibodies. The new ones appear on either side of this isthmus, which organisms may persist in this form for a prolonged persists for some time after the fission. Subsequently period without any reaction from the host. The en- it ruptures and the residual bodies are gradually cysted treponemes and the host coexist more or less resorbed. peacefully, but under propitious circumstances the The possibility of longitudinal fission may be cysts may be transformed again into the usual spiral, categorically denied at present. Sexual activity on the which damages the cells of the host and elicits a part of the treponemes cannot be ruled out, and there response. We shall return to this problem in our http://sti.bmj.com/ is some evidence to suggest this mode ofreproduction. description of ultrathin sections of cysts. Sometimes we may observe thick and thin speci- Studies of ultrathin sections of T. pallidum have mens which are interlaced or lie in apposition. In considerably enriched our knowledge of its structure. other pairs one treponeme is dark or smooth and its The methods of processing the material for ultrathin partner is light or granular. It may be asked whether sections have been described in our previous com- these are not males and females. Their bodies inter- munications. twine and come into contact over certain areas cor- on September 27, 2021 by guest. Protected responding to the mesosomes which are located near Outer membranes the head structure. This seems to admit the possi- In ultrathin sections (approximately 200-250 A bility of sexual reproduction. thick) the outer wall (me) of T. pallidum consists of Another mode of reproduction resorted to in ad- two electron dense layers and one electron transparent verse circumstances consists in the formation of layer (Fig. 2). The cytoplasmic membrane (cm) also spores which subsequently develop into new has three layers. It is separated from the outer wall treponemes. The breakdown into granules is especi- (co) by a space of varying width that contains ally pronounced under the action of penicillin and fibrils (f). In longitudinal sections they appear immune sera. punctate or elongated depending on the plane of Of extreme importance is the ability of treponemes cutting. The cytoplasmic membrane lies over the to form cysts under unfavourable conditions. In- cytoplasm (c) (Fig. 4), where ribosomes (r) are sus- vestigators using light microscopy have expressed pended. Here and there light steUate or polygonal divergent opinions about the existence of cysts. structures are visible; these are the nuclear vacuoles Positive electron microscopic evidence has been (N) (Figs 12 and 13). Mesosomes (M) are met with offered only by Ryter and Pillot (1963) as well as occasionally (Fig. 2), looking like laminar formations. ourselves. However, Ryter and Pillot (1963) and The same structures can be found in a transverse Pillot (1965), having correctly described the cysts section. Morphology and biology of Treponema pallidum 317 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
Fibril and Mesosomes Cysts The relation of fibrils to the outer wall is well Finally, a few remarks may be made about the fine demonstrated (Fig. 5). The bundle of fibrils (f) lies structure of cysts (Fig. 8). In ultrathin sections, under the outer wall, but in certain stages of develop- their structure varies (Figs 9 and 10): some of them ment of the treponeme it becomes free; probably have two or three membranes covering the treponeme, the continuity of the outer wall is broken, or maybe which are cut crosswise or longitudinally and contain this bundle stretches like a rubber band and emerges all the formations characteristic for the respective from under the wall. plane of section. The envelopes (mcy) are well de- At the level of a bundle of thick fibrils, the cyto- veloped. Moreover, a cyst may contain laminar bodies plasm contains thinner dark formations, which we of variable dimensions; we believe that these are consider to be deep fibrils (f') (Fig. 5). Formerly we stores of nutrients. Other cysts have one membrane interpreted them as fungiform structures, the sites and the envelopes of the treponeme cannot be clearly of most active metabolism. Further studies of patho- demonstrated or are only partly visible. Evidently genic treponemes have convinced us that these forma- such cysts have undergone degeneration and are not tions are fibrils arranged in a deeper layer. If the outer viable. Typical cysts are characterized by the presence wall is destroyed by special treatment, numerous of membranes and by the preservation of all the deep-lying fibrils become clearly visible, though they structural features of the treponeme. are thinner than those of the superficial layer Can the host harbour cysts of pathogenic tre- (Ovcinnikov and Delektorskij, 1970a) (Fig. 6). ponemes? This is a problem of paramount im- Possibly they also belong to the locomotor apparatus, portance. Even those authors who admit the possi- but effect motion in other directions than the super- bility of encystment of T. pallidum do not consider it ficial fibrils; however, we would prefer to abstain as likely that cysts may exist in host tissues. By meanscopyright. yet from any definite conclusions. of electron microscopy we have succeeded in demon- strating the presence of cysts in a rabbit chancre, and With high magnification it can be seen that each we believe that this observation is of considerable fibril contains an axial thread with a spiral filament significance. wound over it. In sections the fibrils longitudinal The was have cross-striation with periods 1-10. Cut trans- material taken from an 8-month-old to consist of five round structures chancre. When examining the cysts, we could dis- versely, they appear tinctly see multi-layered membranes and treponemes
a central core. http://sti.bmj.com/ surrounding cut in various planes. If we compare sections of pathogenic and cultivated Obviously such a membrane serves as a strong treponemes, we can immediately see that in a culti- barrier to drugs. vated strain the bundle of fibrils is well defined and is intimately related to the overlying outer wall, while Many interesting structural details may be revealed in a pathogenic organism the fibrils are arranged in a by the method of fracturing frozen material. This delicate bundle (Fig. 7), their outlines are indistinct, does not submit the treponemes to any extraneous in- fluences and thus artefacts are avoided. Photomicro- and sometimes they are not covered with the outer on September 27, 2021 by guest. Protected wall. In a cultivated treponeme, the outer wall graphs of specimens processed by this method clearly protrudes over a bundle of fibrils. Obviously this show the granular texture of the space between the protrusion, which is sometimes quite large, suggested cytoplasmic membrane (cm) and the outer wall (co). to some authors the presence of an undulating mem- Several dissimilar formations can be seen in the head brane, but in fact T. pallidum has no undulating structure. Unfortunately, any speculations about their membrane. The sectioned basal granules (Fig. 1) (B) functional significance would be premature. The (Ovcinnikov and Delektorskij, 1966) have the shape cross-striation of fibrils is distinctly visible. of two concentric rings. The structure of mesosomes Comparative electron microscopic studies of varies; they may be ring-shaped or may resemble T. pallidum and T. pertenue have not demonstrated cerebral convolutions. When examining sectioned any clear-cut morphological differences, except for mesosomes, we can clearly observe that they com- the fact that in T. pertenue (Fig. 11) the terminal municate with the exterior and are interconnected by structures are thinner and more acuminate and the long channels situated under the outer wall. Some- mucoid sheath is so thin as to be almost non-existent. times a mesosome has an operculum. However, it Studies of ultrathin sections of T. pallidum have should be emphasized once more that, as far as tre- undoubtedly produced valuable morphological in- ponemes are concerned, the term 'mesosome' formation, but the chief problem facing research evidently encompasses a number of formations workers is the interaction of the treponeme with the performing different functions. body cells, as for instance in a chancre. A detailed 318 British Journal of Venereal Diseases Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
investigation of this problem, and especially re- the duration of their stay within the cells, and their peated examinations performed with the use of viability at the moment of phagocytosis. Usually various drugs, would certainly prove rewarding. phagocytosis is not brought to completion, i.e. The examination of ultrathin sections of affected endocytobiosis predominates. The absorption of tissues may shed light on the main defence mecha- treponemes by the cells is clearly visualized in nisms of the host, help us to understand the function electron micrographs (Figs 14 and 15). The trepo- of various structures both in the treponeme and in neme (T) sinks into a hollow in the cellular membrane, body cells, and define the role of each type of cell and the membrane then closes over it. This process is involved in the pathological process. Such information commonly observed in lymphocytes, plasma cells, may also help to solve the problems of immunology and endothelial cells. Macrophages usually grasp the in the treponematoses. treponemes with their numerous pseudopodia (ps). The main types of cells present in a chancre are Intracellular treponemes may be greatly altered lymphocytes, plasma cells, fibroblasts, and other and may undergo digestion (Figs 16, 16a, 17). An connective tissue cells. Polymorphonuclear leucocytes active role in this process is played by lysosomes or participate to a greater or less degree in only some phagosomes (ph). phases of the development of the chancre (Ovcinnikov Cellular activity and the digestion of engulfed and Delektorskij, 1970b). treponemes are enhanced after an injection of penicillin. Studies of an established chancre aged 3 to 8 weeks It is especially interesting to study treponemes In a rabbit chancre T. pallidum may exist both inside within plasma cells. As is known, plasma cells are the and outside cells. Extracellular forms are usually main producers of antibodies and within them im- situated among collagen fibres (Fig. 12). The slide mune globulins are synthetized primarily by the shows endoplasmic reticulum (er), collagen fibrils ribosomes (r). The treponemes engulfed by plasma copyright. (Kl), a lysosome (1), mitochondria (mi), nuclear cells usually remain unaltered (Fig. 18), preserving all membrane (mN), and a nuclear vacuole (N). Fre- their structural features. The organisms lie outside quently there is a light area around the treponeme or inside the cistemae of endoplasmic reticulum (er). (T); thus the impression is created that collagen It should be noted that in the latter case the ribosomes fibres have been locally destroyed. Longitudinal (r) are not distributed outside the cistemae but are sections do not reveal any substantial difference in structure between extracellular treponemes in a http://sti.bmj.com/ chancre and organisms in a suspension prepared from a chancre or an orchitic lesion, but we often KEY TO THE FIGURES find specimens surrounded with a two- or three- f - fibrils layered membrane, which is situated at a certain dis- - second layer of fibrils tance from the body of the treponeme (T) (Fig. 13). me - outer wall What is the origin of this membrane? Is it related to cm - cytoplasmic membrane co - the outer wall and the cytoplasmic membrane of the outer envelope or 'casing' on September 27, 2021 by guest. Protected treponeme or does it represent an accessory envelope B - basal granules produced by the invading organism or the cellular N - nuclear vacuole elements for protective purposes? The latter suppo- M - mesosome sition cannot be disproved by the extracellular r - ribosome mcy - common envelope of the cyst as it be surmised localization of the treponemes, may c - cytoplasm that they previously existed within cells, and were er - endoplasmic reticulum then enveloped in an isolating membrane and xlKI - collagen fibrils extruded. It is more likely that, in the majority of - lysosome cases, this protective envelope is formed by the mi - mitochondria treponeme or, sometimes, by a combination of the Ps - pseudopodia outer wall and an accessory membrane. Finally, it is T - treponeme possible that in a few cases the section actually shows Tpl - treponemes in state of lysis part of an engulfed treponeme covered with a thin ch - chromatin the that the mN - nuclear membrane cellular membrane; impression organism KS - crystalloid structure is located extracellularly is due to an artefact caused TL - L-forms of treponeme by cutting the section. ri - rounded inclusion The morphology of intracellular treponemes ph - phagosome depends on the types of cells that have engulfed them, DNA - deoxyribonucleic acid Morphology and biology of Treponema pallidum 319 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from copyright. http://sti.bmj.com/
i i(;. 1 IBusaI rauldS ant tik7bril of T- pallidLi on September 27, 2021 by guest. Protected 300.000 FIG. 2 U/rrad,i sctiO OfT. pallidlum Strain 2. 8-e 8aI, roX t I .1I 4 0D
IG3 lrh sdcm i FIG. 3 Ultrathin section of T. pallidum Strain 2. x 80,000 320 British Jfournal of Venereal Diseases Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
c s - \ .. 4o,me.....
/ :1' c* :;me. .d....:
pallidux2000 FIG.4aOuter envelope (casin~g') oftreponemecleary visible x 180,00
C)~ ~ ~ ~ ;'-
cm~~~~~~.; copyright.
4~~~~~~~~::.. http://sti.bmj.com/ on September 27, 2021 by guest. Protected
iw
AM'
FIG. 5 Ultrathin cross-section of T. FIG. 6 Fibrils and second layer offibrils. T. pallidum. x 180,000 pallidum Kazan strain, 8-day growth. x 120,000 Morphology and biology of Treponema pallidum 321 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
.1 .-,. 7 'li 11;Ij1- iss .,1 R-I __ /o t
4.O o If 'aIye
FIG. 7 Bundles offibrils of T. pallidum. x 140,000 k:>Vm...y.7
-1. copyright.
FIG. 8 T. pallidum Nichols strain from a 7-day- http://sti.bmj.com/ old orchitis. Negative-contrast method shows the organism packed into a cyst. x 20,000 (S z .< i. b .gmc .
.t
ttt< on September 27, 2021 by guest. Protected
/ 4. FIG. 11 T. pertenue under the electron microscope. Negative contrast method. x 25,000
cm .- men ~ I 3 - ....3 w 4 ... :
I. .t
: .. :,~~~
mcy
FIG. 9 and FIG. 10 Ultrathin sections of a cyst of T. pallidum. x 120,000 and x 60,000 322 British Journal of Venereal Diseases Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from copyright. http://sti.bmj.com/ A -I tA *4_. e .~ KL
O
- r on September 27, 2021 by guest. Protected
4a~~~~
. ' ' Y '~ ''iTet
FIG. 12 Ultrathin section from a rabbit infected with Nichols strain, showing T. pallidum among collagen fibrils. x 50,000 FIG. 13 Ultrathin section of Nichols strain, showing multi-layered outer wall. x 12,000 Morphology and biology of Treponema pallidum 323 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
as,.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. er
PS '4 ';3§4'~~~~~~~~~~~~~0 copyright. http://sti.bmj.com/ .,.~~:t*s ~ ~ j; b - t t s ;~~~~~~~Jf o ^4,,.,,a- ~~~KL-- ,,> on September 27, 2021 by guest. Protected
+.*~'i g. r * <,.,6 X P Om"~~~e A4 TpL r IP- 4 q -4,~~~ ~ ~ ~ ~ ~ ~ ~ 4 6 41~~~~~~~~~~~~~
FIG. 14 Ultrathin section of material from the site of a chancre, showing intact T. pallidum inside a cell. x 50,000 FIG. 15 Treponemes lying outside the cell in a state of lysis. x 40,000 324 British Journal of Venereal Diseases Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from
L16) 4 ;;x,vz(I
ch~ ttD<4 b , ' ¢ _ _ Q93tSt ''''KU)t 'i?wS
,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A
t' W §yat -1 :j! *i\"'r.~~.i< Wv' ,, 'v''s k copyright. a'a http://sti.bmj.com/ ka* T * :SB7 on September 27, 2021 by guest. Protected w.7 .7'.4. FIG. 16 Ultrathin section from a 6-week-old chancre taken 15 min. after administration of penicillin. Chromatin (ch) surrounds nuclear vacuoles (N). x 8,000 FIG. 16a Detail. x 25,000 FIG. 17 Treponemes (T) in a phagosome (ph) in a state of lysis. x 25,000 Morphology and biology of Treponema pallidum 325 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from copyright. fZs Ag, A .; http://sti.bmj.com/ *>X r~~~~~~~~~~~~~~~~~S TI, pv * / \~~~~~: ..t AF * x K'., II * .1 4.f R x 0 on September 27, 2021 by guest. Protected _ v S a,. *.. .: eC _ , . ¢, ,WM' -. > 4 b * t r S:,t52pi $j ;at' _ x N _.:- -- .. *-- e _ 4t 7,.:'_ 7$ 41X I .a N:. ..~~~ r WI.,-*4.4 FIG. 18 T. pallidum inside plasma cells FIG. 19 L-forms of T. pallidum (TL) under the electron microscope, recalling the structure a nucleus with strands,.: w;DNA. x of .. : 21,000 *.... ..l,. ~ ..... :. '.7s < <|t 4,93 ,. -: .. '. ..4tS .S.',,td~ SA~ ~ ~ copyright. http://sti.bmj.com/ on September 27, 2021 by guest. Protected k210) *..21; ... ..t FIG. 20 L-forms of T. pallidum with different degrees of electron density. One contains a rounded inclusion (ri). x 21,000 FIG. 21 T. pallidum Strain 8, showing a crystalloid structure (Ks). x 120,000 M-Morphology and biology of Treponema pallidum 327 Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from orientated inwards facing the antigen. In plasma cells example, gonococcus, Proteus vulgaris, etc. When and macrophages, the treponemes are frequently L-forms are transferred to the usual media they soon covered with a kind of membranous sheath, and reverse to the original forms. For some time they provided with dense envelopes. All this signifies that may be found among typical treponemes, but subse- in plasma cells the treponemes are well protected, quent preparations studied by phase contrast or evade destruction, and may subsist for a long time. electron microscopy show only ordinary forms of We have advanced the suggestion that the prolonged T. pallidum. Some of them are seen to divide. formation ofantibodies and the persistence of positive Fig. 20 shows a rounded inclusion (ri). serological reactions in syphilis may be explained by Thus it is evident that T. pallidum may produce the presence of the antigen in plasma celUs. This is L-forms under conditions of stress. In our experi- especially likely since the latter may migrate into the ments the organisms were stressed with penicillin, blood vessels, be carried into distant organs little ac- various drugs, antisera, etc., and the addition of these cessible to antibiotics, and exist there for a long time. agents led to the appearance of L-forms. We have not Treponemes harboured in the cisternae of a plasma yet isolated L-forms directly from animals affected cell have been obtained from a rabbit with an 8-month- with syphilis, but undoubtedly they can be present old chancre previously treated with penicillin. in rabbit tissues. Most treponemes reside in interstitial spaces, The significance of these data can hardly be over- where great numbers of organisms are sometimes estimated if we recall that conversion to L-forms found. alters the clinical course of a disease, the virulence Attention should be paid to the distribution of and pathogenicity of the organisms, their antigenic treponemes around blood vessels and sometimes activity, drug resistance, and other properties, not to even within the lumina. By way of the interstitial mention the diagnostic difficulties presented by such spaces the treponemes may gain access to the blood variants. copyright. stream or penetrate from the vessels into the tissues. It should be noted that in some preparations of the This fact explains the high incidence of treponemes in treponemes we have found crystalloid structures perivascular areas, where they are usually located (KS), especially after the addition of penicillin (but extracellularly. The data obtained emphasize, more- also without it) and during the reversion of L-forms. over, the intimate interrelation between thc lymphatic The crystalloids had a three-dimensional symmetry and the haematogenous routes. Moving along the and resembled protein paracrystals (Figs 21, 21a). lymphatic spaces the organisms may penetrate into The significance of these formations has not been the blood vessels. established. http://sti.bmj.com/ The morphological appearance of T. pertenue in rabbit lesions and its interaction with the body cells Summary are similar to the processes observed in syphilis, except for a more pronounced plasmocytic response, (1) Electron microscopy of T. pallidum has re- and more fully developed laminar membranes vealed a number of structural features: a sheath, a around the intra- and extracellular treponemes. three-layered outer wall, a cytoplasmic membrane also consisting of three layers, superficial and deep on September 27, 2021 by guest. Protected L-forms bundles of fibrils, a nuclear vacuole, mesosomes, and In collaboration with Dr L. M. Ustimenko we have ribosomes. Each of these formations has a complex produced experimentally L-forms of cultivated strain structure. No. 8 (Ovcinnikov, Delektorskij, and Ustimenko, (2) Transverse fission is the main mode of re- 1970). production of T. pallidum. Under adverse conditions Control photomicrographs made by phase contrast spherulation and encystment may be observed. The microscopy illustrate the original material, consisting possibility of sexual reproduction cannot be excluded. of specimens typical for this strain. Subsequent (3) The structure and motility of cysts, and the photomicrographs demonstrate L-forms-large and circumstances of their appearance, prove that encyst- small spherical bodies of variable density. In electron ment is an adaptive mechanism of survival. micrographs showing ultrathin sections of L-forms, a thin membrane (Figs 19, 20) is visible, as well as (4) Under the action of penicillin or antiserum, in dimension, and electron T. pallidum in culture produces L-forms, which formations varying shape, if transferred to density. Some are homogenous, others granular, and reverse to the original spiral forms still others have the structure of a nuclear vacuole. media lacking these agents. The L-forms of T. pallidum do not differ significantly (5) In chancre tissues, T. pallidum may be located in appearance from those of other organisms, for both inside and outside cells. Macrophages, plasma 328 British Journal of Venereal Diseases Br J Vener Dis: first published as 10.1136/sti.47.5.315 on 1 October 1971. Downloaded from cells, endothelial cells, monocytes, and polymor- game, une paroi externe form&e de trois couches, une phonuclear leucocytes actively participate in phago- membrane cytoplasmique consistant egalement en trois cytosis. As a rule, phagocytosis is not brought to couches, des paquets de fibrilles superficielles et pro- completion (endocytobiosis predominates). fondes, une vacuole nucleaire, des mesosomes et des ribosomes. Chacune de ces formations a une structure (6) Penicillin enhances cellular activity; after an complexe. injection complete phagocytosis may be demon- (2) La separation transversale est le principal mode de strated. reproduction du T. pallidum. Lorsque les conditions (7) The persistence of positive serological reactions sont defavorables, on peut observer la formation de may be explained by the prolonged presence of spheres et de kystes. La possibilite de reproduction unaltered treponemes within plasma cells. sexuee ne peut pas etre exclue. (3) La structure et la mobilite des kystes ainsi que les References circonstances de leur apparition prouvent que l'enkyste- OVINNIKOv, N. M., and DELEKTORSKIJ, V. V. (1966) ment est un mecanisme adapte a la survie. Bull. Wld Hlth Org., 35, 223 (4) Sous l'action de la penicilline ou d'un anti-serum, le (1968) Brit. J vener. Dis., 44, 1 T. pallidum en culture produit des formes L qui retoument (1969) Ibid., 45, 87 aux formes spiralees originelles apres transport dans des (1970a) Ibid., 46, 349 milieux depourvus des agents cites. (1970b) Bull. Wld Hlth Org., 42, 437 (5) Dans les tissus chancreux, le T. pallidum peut etre -,-, and USTIMENKO, L. M. (1970) 'L-forms of detecte a la fois a l'interieur et a l'exterieur des cellules. Treponema pallidum'. WHO/VDT/RES/70, 225 Les macrophages, les plasmocytes, les cellules endothe- PILLOT, J. (1965) These, Serie A, No. 4571, Lons-le- liales, les monocytes et les polynucldaires participent Saunier, France activement a la phagocytose. Habituellement, la phago- RYTER, A., and PILLOT, J. (1963) Ann. Inst. Pasteur, cytose n'arrive pas a etre totale (l'endocytobiose pre- 104, 496 domine). Conceptions courantes sur la morphologie et la (6) La p6nicilline stimule l'activite cellulaire; apres une copyright. biologie du Treponema pallidum fond6es sur la injection, une phagocytose compIte peut etre mise en microscopie 6lectronique evidence. SOAMMIRE (7) La persistance de reactions serologiques positives peut (1) Les etudes du T. pallidum au microscope electronique etre expliquee par la presence prolong&e de treponemes ont revele nombre de faits concemant sa structure: une alteres a l'interieur des plasmocytes. http://sti.bmj.com/ on September 27, 2021 by guest. Protected