Library

Notes: The parasitic protozoan Trichomonas vaginalis is known to contain the ubiquitous and highly conserved protein actin. A genomic library and a cDNA library have been screened to identify and clone the actin gene(s) of T. vaginalis. The nucleotide sequence of one gene and its flanking regions have been determined. The open reading frame encodes a protein of 376 amino acids. The sequence is not interrupted by any introns and the promoter could be represented by a 10 bp motif close to a consensus motif also found upstream of most sequenced T. vaginalis genes. The five different clones isolated from the cDNA library have similar sequences and encode three actin proteins differing only by one or two amino acids. A phylogenetic analysis of 31 actin sequences by distance matrix and parsimony methods, using centractin as outgroup, gives congruent trees with Parabasala branching above Diplomonadida.

Notes: . The amitochondrial flagellates comprise the Archamoebae, the Metamonada (orders: Retortamonadida, Diplomonadida, Oxymonadida) and the Parabasala. Molecular rDNA sequence comparison has shown that the diplomonads are very ancient and placed at the base of the tree, but the position of the parabasalids before or after the Euglenozoa and other mitochondriate protists is not definitively determined and such molecular data are required to place the other groups. Common cytological features such as one basal body and a basal body-nucleus connector show that the mastigamoebids or Archamoebae are an evolutionary lineage. The metamonad grouping is heterogenous; the three orders have in common two pairs of basal bodies, no Golgi and could be poly- or paraphyletic. The Parabasala is an evolutionary lineage with a large set of homologous cytological characters. A biochemical study of the cytoskeletal structures such as costa, parabasal fibre, preaxostylar fibre and undulating membrane in trichomonads reveals a large diversity in the protein composition among the genera that fits with the large distance between the taxa estimated by rDNA sequencing. Molecular comparison in seven tnchomonad genera indicates that the Trichomonadinae and Tritrichomonadinae form two divergent branches, the genera Hypotrichomonas and Monocercomonas are now incorporated in the tritrichomonad branch, and Trichomitus is at the bifurcation of the two branches. This scheme is different from the classic tree but not incompatible with it.

Notes: Ce Tetradimorpha, rencontre en eau douce se présente soit sous forme sphérique pourvue de quatre flagelles et d'axopodes rayonnants, soit sous forme allongée avec a l'avant quatre flagelles associes a quatre axopodes et a l'arriére six a huit axopodes divergents. L'etude ultrastructurale révèle un cytosquelette axopodial de type centroplastidie comprenant un centroplaste lenticulaire homogéne, centre organisateur des quatre axopodes anterieurs et des six a huit axopodes posterieurs, auquel s'ajoutent les quatre cinetosomes des flagelles anterieurs. En outre, un deuxiéme éleément cytosquelettique incluant un microtubule associe chacun des quatre cinetosomes a l'axopode antérieur correspondant. Des cordons microfibrillaires réunissent axopodes et cinetosomes au niveau du centroplaste, puis a quelque distance du centroplaste les axopodes posterieurs. Les axonémes des axopodes comprenant de 5 a 30 microtubules sont constitues de triades, lorsqu'on peut détecter une organisation. Le noyau, a nucléole central est coince dans le cone axopodial posterieur, lui-méme entouré des dictyosomes. Par l'organisation du cytosquelette, par la structure des kinétocystes, par la structure des flagelles dépourvus de mastigonémes tubulaires, Tetradimorpha différe nettement de Ciliophrys marina. Comme le prévoyait Davidson (1975), il represönte bien un des chainons dans la série évolutive des Héliozoaires centrohélidiens. Mais il ne présente guère d'affinites avec les Chrysomonadines considerees comme la souche des Héliozoaires. L'intéret de ce Protiste dans l'étude de la differentiation et de l'evolution du cytosquelette est également présente.〈section xml:id="abs1-2"〉〈title type="main"〉ABSTRACTThis freshwater species of Tetradimorpha has a spherical body with four flagella and radiating axopods; it transforms into a pear-shaped cell that anteriorly has four flagella intercalated between four axopods and posteriorly has six to eight divergent axopods. Ultrastructural study reveals an axopodial cytoskeleton of the centrohelidan type comprising an homogeneous lenticular centroplast which acts as MTOC for axopodial microtubules. A second skeletal element is a microtubular linkage between the kinetosomes and the axonemes of anterior axopods. A microtubule embedded in dense material diverges from near the base of each kinetosomes and parallels the distal portion of the axoneme of each anterior axopod. A microfibrillar envelope around the centroplast links the axopodial bases to the kinetosomes situated just above. Close to the centroplast, microfibrillar strands link the axopodial axonemes to the kinetosomes. Axopodial axonemes are composed of 5 to 30 microtubules irregularly arranged except for some that form equilateral triangles. The nucleus containing a central nucleolus is constrained within a cone formed by the axonemes of the posterior axopods and surrounded by dictyosomes. By the cytoskeletal organization, the structure of kinetocysts, and flagella wthout tubular mastigonemes, Tetradimorpha differs obviously from Ciliophrys marina. As Davidson (1975) predicted, Tetradimorpha is an intermediate link in the centrohelidan lineage: however, it lacks the characteristics of chrysomonads, the supposed ancestors of Heliozoa. The contribution of this genus to the study of the differentiation and the evolution of the cytoskeleton is also presented and discussed.

Notes: RESUME. Deux espèces d'Enteromonas sont observées, provenant, l'une de l'intestin de Triton, l'autre des crottes du Lapin domestique. La cellule piriforme porte un noyau antérieur et 4 flagelles insérts près du pôle ventral du noyau. Le flagelle récurrent (R) est logé dans une dépression ventrale ou cytostome. Les cinétosomes, disposés en une paire antérieure (#1, #2) et une paire postérieure (#3, R), sont liés entre eux par des microfibrilles. Une fibre microtubulaire située au-dessus du noyau est reliée au cinétosome #1. Une autre fibre microtubulaire sous-nucléaire est homologue de la fibre microtubulaire croisée qui existe chez les cellules de Diplozoaires. Le cytostome est bordé par 2 lèvres: la gauche proéminente et armée par plusieurs rangées de microtubules, la droite contenant seulement une mince fibre microtubulaire associée à des microfibrilles. Le cytostome occupe les 2/3 de la face ventrale. Le flagelle récurrent pénètre dans le cytostome puis dépasse l'extrémite de la cellule. Les Bactéries sont phagocytées au fond du cytostome, entre les 2 lèvres distendues. Elles sont digérées dans les nombreuses vacuoles et les corps résiduels sont évacués par rupture de la membrane cellulaire. L'ergastoplasme est concentré près de la périphérie de la cellule. Il n'y a pas de mitochondrie ni d'appareil de Golgi. Dans les kystes observés la cellule plurinucléée est enfermée dans une enveloppe kystique microfibrillaire, les axonèmes sont libres dans le cytoplasme.Les formes diplomonades sont nombreuses et ressemblent aux cellules d'Hexamita, excepté par le cytostome qui est différent. Dans ces formes, les 2 monades sont souvent disposées selon une symétrie axiale binaire mais quelquefois elles sont associées de façon plus anarchique. La cinétide d'Enteromonas est organisée comme celle d'un zoïde de Diplozoaire. Il est possible que le genre Enteromonas soit à l'origine des Diplomonadida et que l'état diplomonadien transitoire chez Enteromonas se soit stabilisé ensuite chez les Diplomonadida. Enteromonas apparaît plus primitif que les autres genres de Diplomonadida aussi nous proposons de créer 2 sous-ordres: celui des Enteromonadina avec le genre Enteromonas et celui des Diplomonadina avec les genres Trepomonas, Trigonomonas, Hexamita, Spironucleus, Octomitus, Giardia. La disposition des cinétosomes et l'existence du cytostome sont les principaux caractères communs entre Enteromonas et les Retortamonadida, cependant les fibres annexes ne sont pas homologues. Une étude plus complète de la division nucléaire et cellulaire de ces 2 ordres de Zooflagellés est nécessaire pour donner un meilleur schéma évolutif.SYNOPSIS. Fine structure of 2 species of Enteromonas, one from the intestine of the salamander, Triturus vulgaris, and another from the feces of domestic rabbit, Oryctolagus cuniculi, is described. The pyriform cell has an anteriorly located nucleus. The 4 flagella originate from an area near the anterior end of the nucleus. The recurrent flagellum (R) is lodged in a ventral depression or cytostome. The kinetosomes, arranged into 2 pairs, anterior (#1, #2) and posterior (#3, R), are interconnected by microfibrils. One microtubular fiber, connected to kinetosome #1, is situated near the anterior surface of the nucleus. Another, subnuclear, microtubular fiber is homologous to the “crossed'’fiber found in Diplozoa. The cytostome is bordered by 2 lips: the preeminent left lip is equipped with several rows of microtubules, while the right lip contains only a thin microtubular fiber associated with microfibrils. The cytostome occupies 2/3 of the ventral surface. The recurrent flagellum passes over the anterior surface of the cell and then comes to lie in the cytostome. The bacteria are phagocytosed in the bottom part of the cytostome between the 2 distended lips. They are digested in numerous vacuoles. The undigested residual bodies are evacuated by a rupture of the cell membrane. The ergastoplasm is concentrated near the cell periphery. Mitochondria and the Golgi apparatus are absent. In the cyst stage, the multinucleate cell is enclosed in a microfibrillar membrane; the axonemes lie free in the cytoplasm.Diplomonad forms of Enteromonas resembling Hexamita are numerous, except that the cytostome is different in these 2 genera. In such forms, the arrangement of the 2 individuals often has binary axial symmetry, but on occasion they are associated in a more anarchic fashion. The mastigont of Enteromonas is organized like that of a single zooid of a diplozoon. It is possible that the genus Enteromonas is ancestral to Diplomonadida and that the diplomonad state, transitory in Enteromonas, became permanently established in Diplomonadida. Enteromonas appears to be more primitive than the other genera of Diplomonadida. Thus we propose 2 suborders: Enteromonadina, subord. nov. with the genus Enteromonas, and Diplomonadina Wenyon, emend., with the genera Trepomonas, Trigonomonas, Hexamita, Spironucleus, Octomitus, Giardia. The arrangement of the kinetosomes and the existence of a cytostome are the principal characters common to Enteromonas and Retortamonadida, while their “accessory'’fibers are not homologous. A more complete study of division of the 2 zooflagellate orders is necessary for the presentation of a more detailed evolutionary scheme of these groups.

Notes: Abstract. This revision of the classification of unicellular eukaryotes updates that of Levine et al. (1980) for the protozoa and expands it to include other protists. Whereas the previous revision was primarily to incorporate the results of ultrastructural studies, this revision incorporates results from both ultrastructural research since 1980 and molecular phylogenetic studies. We propose a scheme that is based on nameless ranked systematics. The vocabulary of the taxonomy is updated, particularly to clarify the naming of groups that have been repositioned. We recognize six clusters of eukaryotes that may represent the basic groupings similar to traditional “kingdoms.” The multicellular lineages emerged from within monophyletic protist lineages: animals and fungi from Opisthokonta, plants from Archaeplastida, and brown algae from Stramenopiles.

Notes: . The flagellar apparatus of four heterolobosean species Percolomonas descissus, Percolomonas sulcatus, Tetramitus rostratus, and Naegleria gruberi were examined. P. descissus lives in oxygen-poor water. It is a quadriflagellated cell with a ventral groove. The two pairs of basal bodies are connected to an apical structure from which the peripheral dorso-lateral microtubules and a short striated rhizoplast originate. There is one major microtubular root, Rl, which originates from the posterior basal body pair and splits into left and right portions that support the sides of the ventral groove. The anterior pair of basal bodies is associated with a root of four to five microtubules that runs to the left of the groove. This organisation is similar to that previously reported for Psalteriomonas, Lyromonas, and Percolomonas cosmopolitus. Percolomonas sulcatus has two parallel pairs of basal bodies, each of which is associated with a well-developed Rl root. These roots divide to give two distinct left portions and one merged right portion that support the margins of the slit-like ventral groove. Tetramitus rostratus has two pairs of basal bodies, several rhizoplast fibres, and two Rl roots. Each Rl root supports one wall of the ventral groove. Naegleria gruberi may have two pairs of basal bodies, each associated with a microtubular root and one long rhizoplast fibre. From available data, a ‘double bikont’-like organisation of the heterolobosean flagellar apparatus is inferred, where both of the eldest basal bodies have largely ‘mature’ complements of microtubular roots. The cytoskeletal organisation of heteroloboseans is compared to those of (other) excavates. Our structural data and existing molecular phytogenies weaken the case that Percolomonas, Psalteriomonas, and Lyromonas are phylogenetically separable from other heteroloboseans, undermining many of the highest-level taxa proposed for these organisms, including Percolozoa, Striatorhiza, Percolomonada, Percolomonadea, and Lyromonadea.

Notes: Deux types de structure kystique ont été observés au microscope éectronique. Dans le ler, qui correspond aux kystes d'infection ou gamontokystes, la cellule est relativement libre dans l'enveloppe kystique. Celle-ci est formée de 2 couches distinctes d'inégale épaisseur (ectokyste, endokyste) sécrétées par la cellule et doublées intérieurement par un mince feuillet cytoplasmique dûà une extension des plis cuticulaires. C'est la seule modification du cortex cellulaire.Par contre, dans le 2ème type les modifications sont beaucoup plus importantes. La cellule est étroitement accolée aux parois du kyste; crêtes et flagelles ont disparu de la surface. Cependant on retrouve leurs traces dans la région corticale, sous forme d'axonèmes intracytoplasmiques plus ou moins désorganisés et d'empilements de saccules associés à des rangées de microtubules. Ce seraient des kystes de résistance. Les structures observées dans ces derniers kystes nous permettent de discuter quelques idées sur la participation des microtubules et des systèmes membranaires à la morphogénèse du cortex des Opalines.

Notes: L'organisation cellulaire et la structure des organites de Chilomastix aulastomi sont étudiées en microscopie électronique.La cellule est limitée par une pellicule constituée de la membrane cytoplasmique, d'un feuillet continu de microtubules reliés les uns aux autres et, en certains endroits, d'une couche de microfibrilles.Les cinétosomes disposés en 2 paires et orthogonaux deux à deux, sont liés entre eux par du matériel microfibrillaire. Le flagelle récurrent porte 2 expansions aliformes.La lèvre droite du cytostome est armée d'une fibre qui présente une structure soit microtubulaire, avec des éléments jointifs enrobés dans un matériel microfibrillaire osmiophile dans la partie antérieure, soit périodique et paracristalline dans sa partie postérieure.La lèvre gauche du cytostome contient également une fibre constituée de microtubules jointifs et de microfibrilles. Un arceau de microfibrilles réunit les 2 lèvres du cytostome à son sommet. Les fibres des lèvres cytostomiennes sont reliées aux microtubules sous-pelliculaires.L'endocytose se réalise dans le cytopharynx, placé en prolongement du cytostome et en des points dépourvus de microtubules sous-membranaires.L'hémifuseau de division a été observé. Il n'y a ni mitochondrie, ni appareil de Golgi.La cellule enkystée conserve ses organites dans le cytoplasme: cinétosomes, flagelles, fibres du cytostome. Les microtubules sous-membranaires disparaissent, à l'exception d'un rideau intracytoplasmique au pôle apical. La paroi du kyste, épaisse de 0,4 μm, est constituée, d'une épaisse couche de matériel microfibrillaire. Il n'y a pas d'opercule ni de pore. La sécrétion de cette paroi est précédée de l'accumulation de vésicules à contenu granuleux dans le cytoplasme de la cellule.L'organisation et les structures de Chilomastix sont comparées à celles des autres genres de Retortamonadida et aux groupes de Zooflagellata voisins: Kinetoplastida, Diplomonadida, Trichomonadida.〈section xml:id="abs1-2"〉〈title type="main"〉SYNOPSISFine structure of Chilomastix aulastomi was studied by electron microscopy.In the trophozoite, the cell is surrounded by a pellicle composed of a cytoplasmic membrane, a continuous layer of interconnected microtubules, and in certain regions, of a layer of microfibrils. Kinetosomes, arranged in 2 orthogonal pairs, are interconnected by microfibrillar material. The recurrent flagellum has 2 wing-like extensions. The right lip of the cytostome is equipped with a fiber whose anterior part consists of interconnected microtubules embedded in osmiophilic microfibrillar material; the posterior part has a periodic and paracrystalline structure. The left cytostomal lip also contains a fiber made of linked microtubules associated with microfibrils. An arch of microfibrils connects the 2 lips at the anterior edge of the cytostome. The cytostomal fibers are connected to the subpellicular microtubules. Endocytosis takes place in the cytopharynx, which is an extension of the cytostome, but only in areas free of the pellicular microtubules. A “hemispindle” was seen in division. There are neither mitochondria nor Golgi apparatus.The encysted cell retains all its cytoplasmic organelles, including kinetosomes, flagella, and cytostomal fibers. The pellicular microtubules disappear, except for an intracytoplasmic row at the apical pole. The cyst wall, 0.4 μm thick, consists of a thick layer of microfibrillar material. There is no operculum or pore. Secretion of the cyst wall is preceded by an accumulation of vesicles with granular content in the cytoplasm.The fine structure of Chilomastix is compared to that of other genera of the order Retortamonadida, as well as of other zooflagellate groups, such as Kinetoplastida, Diplomonadida, and Trichomonadida.

Notes: . Several domains of large subunit rRNA from nine trichomonad species have been sequenced. Molecular phylogenies obtained with parsimony and distance methods demonstrate the trichomonads are a monophyletic group which branches very early in the eukaryotic tree. the topology of the trees is in general agreement with traditional views on evolutionary and systematic relationships of trichomonads. A clear dichotomy is noted between the subfamily Trichomonadinae and the subfamily Tritrichomonadinae. In the latter subfamily, a second division separates the “Tritrichomonas muris-type” species from the “Tritrichomonas augusta-type” ones. Previous evolutionary schemes in which the Monocercomonadidae were regarded as the most “primitive” and the Trichomonadidae as more “evolved” are not in agreement with our molecular data. the emergence of Monocercomonas and Hypotrichomonas at the base of the Tritrichomonas lineage suggests a secondary loss of some cytoskeletal structures, the costa and undulating membrane in these genera. This is corroborated by the early branching position of Trichomitus. which possesses a costa and an undulating membrane and has usually been placed among the Trichomonadidae on the basis of cytological characters. A cladistic analysis was applied to the available morphological characters in order to produce a hierarchical grouping of the taxa reflecting their morphological diversity. Supplementary key words. Evolution, molecular phylogeny, morphological cladistic analysis.

Notes: . Oxymonas has the characteristic structures and organization of other oxymonads including two separated pairs of basal bodies/flagella, a preaxostylar lamina, a paracrystalline axostyle, and an absence of mitochondria and Golgi. Like other Oxymonadinae genera it possesses a long proboscis, the rostellum which is terminated by the holdfast. Like the genera Pyrsonympha and Streblomastix, Oxymonas possesses a holdfast which permits it to attach to the cuticle of the termite hind-gut. This holdfast is subdivided into rhizoids and is filled with microfilaments. The rostellum is variable in length and contains two distinct microtubular bundles. One bundle is composed of convoluted microtubular ribbons which originate at the base of the holdfast and extend posteriorly along the rostellum and before penetrating into the cell body. The second bundle is composed of flexuous free microtubules which originate at different levels of the rostellum, increasing in number from top to base. They occupy the axial part of the rostellum and incorporate into the axostylar rows at the basal body/flagellar level. Microtubules of the paracrystalline axostyle are cross-linked by bridges forming parallel rows like in the contractile axostyles of other oxymonads such as Pyrsonympha and Saccinobaculus. Most of the microtubules of the axostyle originate at the flagellar/preaxostylar level but some originate from the axial flexous free microtubules of the rostellum, as indicated above. The possibility of an extension/retraction of the rostellum, suggested by other authors, is discussed.