Bursaria Truncatella Research Articles

Catalysis of Chlorovirus Production by the Foraging of Bursaria truncatella on Paramecia bursaria Containing Endosymbiotic Algae.

Chloroviruses are large viruses that replicate in chlorella-like green algae and normally exist as mutualistic endosymbionts (referred to as zoochlorellae) in protists such as Paramecium bursaria. Chlorovirus populations rise and fall in indigenous waters through time; however, the factors involved in these virus fluctuations are still under investigation. Chloroviruses attach to the surface of P. bursaria but cannot infect their zoochlorellae hosts because the viruses cannot reach the zoochlorellae as long as they are in the symbiotic phase. Predators of P. bursaria, such as copepods and didinia, can bring chloroviruses into contact with zoochlorellae by disrupting the paramecia, which results in an increase in virus titers in microcosm experiments. Here, we report that another predator of P. bursaria, Bursaria truncatella, can also increase chlorovirus titers. After two days of foraging on P. bursaria, B. truncatella increased infectious chlorovirus abundance about 20 times above the controls. Shorter term foraging (3 h) resulted in a small increase of chlorovirus titers over the controls and more foraging generated more chloroviruses. Considering that B. truncatella does not release viable zoochlorellae either during foraging or through fecal pellets, where zoochlorellae could be infected by chlorovirus, we suggest a third pathway of predator virus catalysis. By engulfing the entire protist and digesting it slowly, virus replication can occur within the predator and some of the virus is passed out through a waste vacuole. These results provide additional support for the hypothesis that predators of P. bursaria are important drivers of chlorovirus population sizes and dynamics.

A guide to Identifying the Species of Bursaria and Fundamental Information of Application of a Large Ciliate Bursaria truncatella to Biology Education.

A guide to Identifying the Species of Bursaria and Fundamental Information of Application of a Large Ciliate Bursaria truncatella to Biology Education.

Gravitaxis of Bursaria truncatella: Electrophysiological and behavioural analyses of a large ciliate cell

Bursaria truncatella is a giant ciliate. Its volume of 3×10 7 μm 3 and a sedimentation rate of 923 μm s −1 would induce the cell to rapidly sink to the bottom of a pond unless compensating mechanisms exist. The upward swimming behaviour of a cell population (negative gravitaxis) may be either a result of reorientations of the cells (graviorientation) and/or direction-dependent changes in propulsion rate (gravikinesis). The special statocyst hypothesis assumes a stimulation of mechanosensitive ion channels by forces of the cytoplasmic mass acting on the lower membrane. Here, we present basic electrophysiological data on B. truncatella. Investigation of the mechanosensitivity reveals a polar distribution of depolarising and hyperpolarising mechanosensitive channels at least on the dorsal membrane of the cell. Analysis of swimming behaviour demonstrates that Bursaria orients against the gravity vector ( r Oc=0.34) and performs a negative gravikinesis (−633 μm s −1) compensating the sedimentation rate by 70%. Under hypergravity conditions gravitaxis in Bursaria is enhanced. Microgravity experiments indicate an incomplete relaxation of graviresponses during 4 s of weightlessness. Experimental data are in accordance with the special statocyst hypothesis of graviperception, as was demonstrated in other ciliates.

Three-dimensional reconstruction of the chromatin structure in the somatic nucleus of the infusorian Bursaria truncatella.

Three-dimensional reconstruction of the chromatin structure in the somatic nucleus of the infusorian Bursaria truncatella.

Phylogenetic position of Sorogena stoianovitchae and relationships within the class Colpodea (Ciliophora) based on SSU rDNA sequences.

The ciliate Sorogena stoianovitchae, which can form a multicellular fruiting body, has been classified based upon its ultrastructure and morphology: the oral and somatic infraciliature of S. stoianovitchae most closely resemble those of members of the order Cyrtolophosidida in the class Colpodea. We characterized the small subunit ribosomal DNA (SSU rDNA) gene sequence from S. stoianovitchae and compared this sequence with those from representatives of all ciliate classes. These analyses placed S. stoianovitchae as either sister to members of the class Nassophorea or Colpodea. In an in-group analysis, including all SSU rDNA sequences from members of the classes Nassophorea and Colpodea and representatives of appropriate outgroups, S. stoianovitchae was always sister to Platyophrya vorax (class Colpodea, order Cyrtolophosidida). However, our analyses failed to support the monophyly of the class Colpodea. Instead, our data suggest that there are essentially three unresolved clades: (1) the class Nassophorea; (2) Bresslaua vorax, Colpoda inflata, Pseudoplatyophrya nana, and Bursaria truncatella (class Colpodea); and (3) P. vorax and S. stoianovitchae (class Colpodea).

Phylogenetic relationships of orders within the class colpodea (Phylum ciliophora) inferred from small subunit rRNA gene sequences

Molecular analyses have been used recently to refine our knowledge of phylogenetic relationships within the ciliated protozoa (phylum Ciliophora). A current Hennigian phylogeny of the orders in the class Colpodea, based on light and electron microscopic analyses, makes three important assumptions with regard to apomorphic character states, namely, (1) that the kreyellid silver line evolved early in colpodean phylogeny, separating bryometopids, such as Bryometopus, from all other colpodeans; (2) that the macro-micronuclear complex is an autapomorphy of the cyrtolophosidids, such as Platyophrya; and (3) that merotelokinetal stomatogenesis is an apomorphic character of colpodids, such as Colpoda, Bresslaua, and Pseudoplatyophrya. These predictions of relationships within the class Colpodea were investigated by determining the complete small subunit rRNA gene sequences for the colpodid Bresslaua vorax, the grossglockneriid Pseudoplatyophrya nana, and the cyrtolophosidid Platyophrya vorax and a partial sequence for the bryometopid Bryometopus sphagni. These sequences were combined with the previously published complete SSrRNA sequences for the colpodid Colpoda inflata and the bursariomorphid Bursaria truncatella. The affiliations were assessed using both distance matrix and maximum-parsimony analyses. The tree topologies for the class Colpodea were identical in all analyses, with bootstrap support for bifurcations always exceeding 60%. The results suggest the following. (1) Since the clade including Bryometopus and its sister taxon, Bursaria, is never basal, the kreyellid silver-line system evolved later in colpodean phylogeny and does not separate bryometopids from all other colpodeans. (2) Since Platyophrya is always the sister taxon to the other five genera, there is a fundamental phylogenetic significance for its macro-micronuclear complex. (3) Since the colpodids, Colpoda, Bresslaua, and Pseudoplatyophrya, always group in one clade, merotelokinetal stomatogenesis appears to be a derived character state.

Ultrastructure of the macronucleus in the resting cysts of the ciliate Bursaria truncatella

Summary The ultrastructure of the macronucleus and the micronucleus in the resting cysts of the ciliate Bursaria truncatella was studied by electron microscopy. The data obtained were compared with those for B. truncatella mature vegetative cells. Macronuclear chromatin in the resting cysts was shown to be organized in compact electron-dense bodies twice to three times as large as those in the vegetative B. truncatella cells completed their growth and differentiation. In the cyst macronucleus we observed clearly separated zones with chromatin bodies of different morphology. Some of these zones contained large, closely associated chromatin bodies, while smaller, more sparsely distributed ones were observed in others. During encystment the chromatin bodies increase in size at first. Then they fuse into rather extended linear or circular chromatin strands of 150 to 300 nm in diameter, resembling chromonemata that are typical for chromosomes of higher eukaryotes. Nucleoli in the early cysts underwent segregation observed mainly in the cortical regions of the macronucleus. The distribution of RNA-containing structures in cysts and the extrusion of nucleolar material into the cytoplasm were studied using RNase A-colloidal gold complexes. The extrusion of nucleolar material appeared to be coupled with the segregation of the nucleoli. The development of chromatin bodies and nucleoli might reflect the functional state of the macronucleus of encysted B. truncatella , indicating that some low transcriptional activity may be left in the cyst macronucleus.

Phylogenetic Relationships between Prostome and Colpodean Ciliates Tested by Small Subunit rRNA Sequences

We analyzed the phylogenetic relationships among the four ciliate classes, Prostomatea, Colpodea, Nassophorea, and Litostomatea, by small subunit ribosomal RNA gene sequence comparison to test several phylogenetic hypotheses that had been proposed for these classes, based on ultrastructural features. The complete coding regions of the prostomes,Prorodon teresandColeps hirtus,and of the colpodean,Bursaria truncatella,were determined and compared to the database and the literature. The prostomes and colpodeans are strongly supported as monophyletic groups in all analyses. A sister-group relationship between prostomes and colpodeans is strongly supported by parsimony analysis and moderately supported by distance matrix analyses. There was no support for a close relationship between colpodeans and nassophoreans or between colpodeans and litostomes. In all analyses, these four classes branch late in the ciliate tree. This finding further supports the new view of ciliate phylogeny that so-called ancestral taxa, such as the “primitive” prostomes, are in fact derived and that so-called “highly evolved” groups, such as the heterotrichs, branch off very early in the ciliate tree.

Electronmicroscopic localization of ribonucleic acids in ciliate Bursaria truncatella during cell division

Highly polyploid somatic nucleus (macronucleus) of ciliate Bursaria truncatella under goes severe changes in morphology during cell division. At first, macronucleus (Ma) condences, diminishes in size and turns perpendicular to longitudinal axis of the cell. After short time, Ma turns again, elongates and only afterwards the process of division itself occurs. The biological meaning of these phenomena is not clear.Localization of RNA in the cells was performed on sections of ciliates B. truncatella, embedded in “Lowicryl K4M” at various stages: (1) before cell division (Figs. 2,3); (11) at the stage of macronucleus condensation; (111) during elongation of Ma (Fig.4); (1111) in young cells (0-5min. after division). For cytochemical labelling we used RNaseAcolloidal gold complexes (RNase-Au), which are known to bind to RNA containing cell ularstructures with high specificity. The influence of different parameters on the reliability and reproducibility of labelling was studied. In addition to the factors, discussed elsewhere, we found that the balance of mono- and bivalent cations is of great significance.

A SEM study of general architecture and cortical patterning in the ciliate Bursaria truncatella O. F. M. during the cell cycle

Summary The general architecture and cortical surface structures have been studied in the giant freshwater ciliate Bursaria truncatella at various stages of its cell cycle: (1) prior to division, (2) during division, (3) after division in the course of differentiation of the new oral apparatus, (4) after completion of differentiation and growth. Changes in the structure of both the somatic and oral ciliatures have been traced. The somatic cilia become sparse during the preparation to division, while before the onset of cytokinesis new cilia arise and grow in the daughter cells after the division. The adorai membranelles and the old perisomal cavity dedifferentiate before the onset of cytokinesis, while new ciliary zones of the peristome and the new peristomal cavities begin to form in early cytokinesis. In the opisthe, the primordium of the new oral apparatus arises later than in the proter. At initial stages of formation of the new oral apparatuses, the primordia of the peristomal cavities and those of the new peristomal ciliary zones are spatially separated in either of the daughter cells. The development of the ventral cut of the peristome margin, typical of B. truncatella , has been followed. In both daughter cells it results from fusion of two apertures, the subapical and the ventral ones. Stages of formation of the superficial cortical structures inside the peristome, leading to the appearance of cirromembranelles, have been demonstrated. Differences in the structural organization of the dorsal surface of the peristome exist between fed and unfed cells. Our SEM study of morphogenesis in B. truncatella lends support to the transfer of this ciliate from the class Polyhymenophorea to the lower ciliate class Kinetofragminophorea and to the creation of a special order Bursariida in it. Some of the structures observed may be used as morphological markers when studying the regulatory mechanisms of morphogenesis in ciliates.

Electron microscopic and autoradiographic study of the macronuclear chromatin of Bursaria truncatella at different times after cell division

Interphase macronuclear chromatin of the ciliate Bursaria truncatella was studied on spread preparations of individual nuclei isolated at different times after vegetative division. During the period from 0.5 to 3 h after cell division most of the macronuclear chromatin was in the decompacted state and had the appearance of loose agglomerations of fibers in regions where transcriptional complexes were observed. The maximum amount of decompacted chromatin was observed 0.5–1.5 h after cell division. At 2–3 h after division the amount of decompacted chromatin decreased as the amount of compact chromatin organized in clumps 0.12–0.18 μm in diameter increased. Macronuclei from cells that had finished growing and differentiating contained practically only linked chromatin clumps. Electron microscopic autoradiography showed that chromatin organized in clumps was transcriptionally inactive. Transcription only took place in decompacted chromatin agglomerations. Characteristic features of the structure of transcriptionally active genes in B. truncatella are described in detail.

Transfer of the Widely Known "Spirotrich" Ciliate Bursaria truncatella O.F.M. to the Vestibulifera as a Separate Order There, the Bursariomorphida

Transfer of the Widely Known "Spirotrich" Ciliate Bursaria truncatella O.F.M. to the Vestibulifera as a Separate Order There, the Bursariomorphida

The effect of phytohemagglutinin on growth and DNA synthesis of some protozoa

The effect of PHA on some protozoa has been studied from several points of view. 1. 1. In Bursaria truncatella, treated with PHA, the mean generation time was shortened from 24–28 hr to about 20 hr. 2. 2. The growth stimulating effect concerned more than one generation of Bursaria when the animals remained in the PHA containing medium. 3. 3. In Stentor coeruleus, collected from a stationary culture, growth and division were initiated by treatment with PHA. 4. 4. Dry mass determination of Paramecium aurelia by soft X-ray microradiography proved that the total mass of recently divided PHA-treated individuals and controls was about the same. 5. 5. DNA measurements of Feulgen stained macronuclei of Paramecium aurelia indicated that the growth stimulus primarily attacked the G1 period. The total amount of DNA, synthesized in the macronuclei within one cell generation, was approximately the same in treated animals and controls.

Effect of Toxins and Venoms upon Protozoa.

Since the completion of a previous study on the effect of pathogenic bacteria and bacterial toxins upon paramecia, an investigation has been in progress on the effect of snake venoms and of toxins (tetanus, ricin and botulinus) upon protozoa. The recent appearance of Tunnicliff's related study with other toxins, and particularly her consideration of the use of paramecia for determining the strength of antitoxins, has made advisable the recording of a preliminary report of the present investigation in so far as it is related to her findings. In the study of the effect of tetanus and botulinus toxins, of ricin and of snake venoms upon protozoa, only the venoms have definitely given positive results. Crotalus atrox (Texas rattlesnake) venom, in dilutions containing 0.00025 gm. per cc, had an immediate lethal effect upon Paramecium caudatum, Stentor coeruleus, Bursaria truncatella and Frontonia leucas. With Volvox spermatosphara and Oxytrichia fallax the venom was lethal in effect but very slow in action. The effect on Chilomonas paramecium was slight and only temporary while Coleps hirtus, Podophyra fixa, and Dileptus gigas were not affected. A race of Paramecium caudatum has thus far lent itself well to and has given consistent results in measurements of the potency of snake venoms. The M.L.D. of Crotalus atrox venom for the race of Paramecium caudatum, in this case the least amount in one cubic centimeter of medium required to kill an animal in 24 hours, was 0.00002 gm. This was one twentieth of the least amount required to kill a 20 gm. mouse. The M.L.D. of Agkistrodon piscivorous (Mocassin) venom for P. caudatum was 0.0000014 gm., while for Bothrops atrox (Fer de lance of Central America) it was 0.0000125 gm. It is evident that the agent in these venoms that is principally responsible for the death of paramecia is thermolabile. It is hoped that further fractionation may make possible the study of the effect of each of the several constituents of venom upon protozoa.