Exocytosis, endocytosis and membrane recycling in Tetrahymena thermophila

1988 ◽  
Vol 89 (4) ◽  
pp. 515-520
Author(s):  
ARNO TIEDTKE ◽  
PETER HÜNSELER ◽  
JORGE FLORIN-CHRISTENSEN ◽  
MONICA FLORIN-CHRISTENSEN
Keyword(s):  
Cell Lines ◽  
Tetrahymena Thermophila ◽  
Food Vacuole ◽  
Secondary Effect ◽  
Membrane Recycling ◽  
Acid Hydrolase ◽  
Wild Type ◽  
Acid Hydrolases ◽  
Vacuole Formation ◽  
Food Vacuoles

Mutant and wild-type cell lines of Tetrahymena thermophila were used to investigate a possible connection between acid hydrolase secretion and the major processes through which membranes are recycled in this ciliated protozoon. These processes consist of food vacuole formation (endocytosis), and food vacuole egestion and mucocyst release (both exocytosis). We have found that a mutant (MS-1, see−) blocked in hydrolase secretion is not blocked in either food vacuole formation or egestion and that it has normal mucocyst exocytosis. Another line of experiments with wild-type cells showed also that hydrolase secretion and endocytosis are independent of each other. Thus, sucrose (0.1m) did not interfere with hydrolase secretion, but blocked food vacuole formation. Furthermore, release of acid hydrolases was selectively stimulated by dibucaine without any effect on food vacuole egestion. Finally, exocytosis of mucocysts could occur without simultaneous release of acid hydrolases, as when cells were exposed to (0.15M-NaCl, which evokes a massive secretory response of mucocysts. Our results demonstrate that formation and egestion of food vacuoles and exocytosis of mucocysts are unrelated to secretion of acid hydrolases. Furthermore, they suggest that secretion of acid hydrolases is not a secondary effect of membrane recycling through these processes.

scholarly journals ADF/Cofilin Is Not Essential but Is Critically Important for Actin Activities during Phagocytosis in Tetrahymena thermophila

2013 ◽  
Vol 12 (8) ◽  
pp. 1080-1086 ◽  
Author(s):  
Nanami Shiozaki ◽  
Kentaro Nakano ◽  
Yasuharu Kushida ◽  
Taro Q. P. Noguchi ◽  
Taro Q. P. Uyeda ◽  
...  
Keyword(s):  
Tetrahymena Thermophila ◽  
Food Vacuole ◽  
Content Type ◽  
Vacuole Formation ◽  
Future Studies ◽  
Cellular Events ◽  
Food Vacuoles

ABSTRACT ADF/cofilin is a highly conserved actin-modulating protein. Reorganization of the actin cytoskeleton in vivo through severing and depolymerizing of F-actin by this protein is essential for various cellular events, such as endocytosis, phagocytosis, cytokinesis, and cell migration. We show that in the ciliate Tetrahymena thermophila , the ADF/cofilin homologue Adf73p associates with actin on nascent food vacuoles. Overexpression of Adf73p disrupted the proper localization of actin and inhibited the formation of food vacuoles. In vitro , recombinant Adf73p promoted the depolymerization of filaments made of T. thermophila actin (Act1p). Knockout cells lacking the ADF73 gene are viable but grow extremely slowly and have a severely decreased rate of food vacuole formation. Knockout cells have abnormal aggregates of actin in the cytoplasm. Surprisingly, unlike the case in animals and yeasts, in Tetrahymena , ADF/cofilin is not required for cytokinesis. Thus, the Tetrahymena model shows promise for future studies of the role of ADF/cofilin in vivo .

Dual capacity for nutrient uptake in Tetrahymena. V. Utilization of amino acids and proteins

1979 ◽  
Vol 36 (1) ◽  
pp. 343-353
Author(s):  
E. Orias ◽  
L. Rasmussen
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Tetrahymena Thermophila ◽  
Amino Acid Uptake ◽  
Food Vacuole ◽  
Transport Systems ◽  
Acid Uptake ◽  
Vacuole Formation ◽  
Carrier Mediated Transport ◽  
Food Vacuoles

We investigated the relative contributions of phagocytosis and plasma membrane transport to the uptake of amino acids and a protein (egg albumin) in amounts which allow Tetrahymena thermophila to grow and multiply. We used a mutant capable of indefinite growth without food vacuole formation (phagocytosis) and its wild type (phagocytosis-competent) isogenic parental strain. Our results suggest that phagocytosis is not required for free amino acid uptake, most or all of which can be attributed to carrier-mediated transport systems, apparently located on the plasma membrane. In contrast, phagocytosis is required for utilization of the protein. Proteins can supply required amino acids in amounts sufficient for growth only when food vacuoles are formed. We conclude that Tetrahymena thermophila either possesses no endocytic mechanisms at the cell surface other than food vacuole formation or, if it does, these putative mechanisms are not capable of nutritionally meaningful rates of protein uptake.

Membrane recycling at the cytoproct of Tetrahymena

1979 ◽  
Vol 35 (1) ◽  
pp. 217-227
Author(s):  
R.D. Allen ◽  
R.W. Wolf
Keyword(s):  
Plasma Membrane ◽  
Single Cells ◽  
Tetrahymena Pyriformis ◽  
Food Vacuole ◽  
Membrane Recycling ◽  
Vacuole Membrane ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Food Vacuoles ◽  
Spherical Vesicles

Exocytosis and membrane recycling at the cytoproct (cell anus) of Tetrahymena pyriformis were studied using thin-section electron microscopy. Single cells were fixed at specific times relative to the elimination of the vacuole's contents—before elimination, at elimination, 3–5 s and 10–15 s following elimination. The closed cytoproct is distinguished from other pellicular regions by a single membrane at the cell surface which is circumscribed by an electron-opaque flange that links or welds the plasma membrane to the underlying alveolar margins. Microtubules originating in the flange pass inward where they lie over, and possibly guide, the approaching food vacuoles to the cytoproct. Food facuoles near the cytoproct are also accompanied by coats of microfilaments. These microfilaments appear to be active in the channelling and endocytosis of food vacuole membrane. Upon cytoproct opening the plasma membrane and food vacuole membrane fuse. Elimination seems to be essentially passive and is accomplished by re-engulfment of the old food vacuole membrane which is constantly associated with microfilaments. Reengulfment of all the food vacuole membrane requires 10–15 s and results in a closed cytoproct. The membrane remnants embedded in microfilaments form a cluster under the closed cytoproct. At the periphery of this cluster remnants take the shape of 70–130-nm spherical vesicles or 0.2-micrometer-long flattened vesicles.

scholarly journals Loss of endocytic capacity in aging Paramecium. The importance of cytoplasmic organelles.

1976 ◽  
Vol 71 (2) ◽  
pp. 575-588 ◽  
Author(s):  
J Smith-Sonneborn ◽  
S R Rodermel
Keyword(s):  
Excretion Rate ◽  
Formation Rate ◽  
Food Vacuole ◽  
Cellular Aging ◽  
Critical Importance ◽  
Vacuole Formation ◽  
Cytoplasmic Organelles ◽  
Food Vacuoles ◽  
Excretion Rates

Aged cells have significantly fewer food vacuoles and ingest fewer bacteria than young cells. Loss of food vacuoles was explained by a decreasing difference in the food vacuole formation and excretion rates; the formation rate declined more rapidly than the excretion rate, approaching equivalence at 160 fissions, when the proportion of cells with no food vacuoles, in the presence of excess food, abruptly increased. A model for cellular aging is presented in which control of organelle numbers and cyclical interactions between the nucleus and cytoplasm may be of critical importance.

Sustained Food Vacuole Formation by AxenicParamecium tetraureliaand the Inhibition of Membrane Recycling by Alcian Blue

1992 ◽  
Vol 39 (6) ◽  
pp. 713-718 ◽  
Author(s):  
EDNA S. KANESHIRO ◽  
STEVEN F. REUTER ◽  
FRANK J. QUATTRONE ◽  
RANDAL E. MORRIS
Keyword(s):  
Alcian Blue ◽  
Food Vacuole ◽  
Membrane Recycling ◽  
Vacuole Formation

The Effect of the H-Ion Concentration on Protozoa, as Demonstrated by the Rate of Food Vacuole Formation in Colpidium

1931 ◽  
Vol 8 (1) ◽  
pp. 17-29
Author(s):  
SYLVIA M. MILLS
Keyword(s):  
Food Vacuole ◽  
Ion Concentration ◽  
Limiting Factors ◽  
Food Ingestion ◽  
Ciliary Movement ◽  
Vacuole Formation ◽  
Alkaline Side ◽  
Food Vacuoles ◽  
Alkaline Range ◽  
Rate Of Movement

1. The effect exerted by the pH of their medium on Colpidium is determined quantitatively by counting the average number of food vacuoles formed in a given time when Colpidium is supplied with Indian ink. 2. Graphs obtained by plotting the rate of feeding against the pH of the medium show a characteristic depression on the alkaline side of neutrality (pH 7.5-8.5), on a curve which otherwise rises steadily from pH 4.5 to a maximum at pH 6.0, and falls from here gradually through the alkaline range. 3. Methods for measuring the rate of movement of ciliates are described, the most practicable being those in which their galvanotropic and geotropic reactions are used to control the direction of the movement. The effect of changes in the pH of the medium on the rate of movement of Colpidium was found to correspond very closely to the effect of similar pHs on the rate of food ingestion. It is, therefore, suggested that changes in the rate of ciliary movement are largely responsible for changes in the rates of food ingestion. 4. Mucus, produced for food collection, and probably also present in the fluid in which the cilia are working, is shown to have a maximum viscosity at pH 8.0. It is suggested that the depression in the region of pH 8.0, seen in curves representing changes in the rates of feeding and movement with pH, indicate that the viscosity of the fluid in which the cilia are beating is one of the limiting factors in the rate of food ingestion through the range of pH occupied by the depression.

scholarly journals MUTANTS OF TETRAHYMENA THERMOPHILA WITH TEMPERATURE-SENSITIVE FOOD VACUOLE FORMATION. I. ISOLATION AND GENETIC CHARACTERIZATION

Genetics ◽  
1979 ◽  
Vol 92 (4) ◽  
pp. 1061-1077
Author(s):  
Peter B Suhr-Jessen ◽  
Eduardo Orias
Keyword(s):  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Complementation Group ◽  
Food Vacuole ◽  
Temperature Sensitive ◽  
Genetic Dissection ◽  
Food Vacuoles ◽  
Per Se ◽  
Oral Development

ABSTRACT Germ-line mutants have been isolated in Tetrahymena thermophila that have recessive, temperature-sensitive defects in phagocytosis. Nitrosoguanidine-mutagenized cells were induced to undergo cytogamy, and clones were isolated that were unable to form food vacuoles after two days of growth at 39°. Most of the mutants belong to a single complementation group, designated vacA. They have defects in oral development—not in phagocytosis per se—that are undetectable under light microscopy. One fertile mutant, phenotypically indistinguishable from the vacA group, has its vac mutation(s) restricted to the macronucleus, and it is a heterokaryon for two other markers. This clone probably resulted from a failure of the two gametic nuclei to fuse after nor,mal exchange. Two additional mutants were studied, but their sterility prevented a full genetic analysis. One of these clones has a rudimentary oral apparatus and defective contractile vacuole pores; both defects may be determined by the same mutation. The other clone has a structurally normal oral apparatus and may be defective in phagocytosis per se.——The induction and characterization of germ-line mutations that affect oral development open the way for the genetic dissection of the morphogenesis of a complex eukaryotic organelle, and make available additional useful mutants for the study of nutrition and transmembrane active transport.

scholarly journals Dynein-2 Affects the Regulation of Ciliary Length but Is Not Required for Ciliogenesis in Tetrahymena thermophila

2009 ◽  
Vol 20 (2) ◽  
pp. 708-720 ◽  
Author(s):  
Vidyalakshmi Rajagopalan ◽  
Aswati Subramanian ◽  
David E. Wilkes ◽  
David G. Pennock ◽  
David J. Asai
Keyword(s):  
Electron Microscopy ◽  
Cell Lines ◽  
Heavy Chain ◽  
Tetrahymena Thermophila ◽  
Intraflagellar Transport ◽  
Cytoplasmic Dynein ◽  
Wild Type ◽  
Mild Phenotype ◽  
Motile Cilia ◽  
Cilia And Flagella

Eukaryotic cilia and flagella are assembled and maintained by the bidirectional intraflagellar transport (IFT). Studies in alga, nematode, and mouse have shown that the heavy chain (Dyh2) and the light intermediate chain (D2LIC) of the cytoplasmic dynein-2 complex are essential for retrograde intraflagellar transport. In these organisms, disruption of either dynein-2 component results in short cilia/flagella with bulbous tips in which excess IFT particles have accumulated. In Tetrahymena, the expression of the DYH2 and D2LIC genes increases during reciliation, consistent with their roles in IFT. However, the targeted elimination of either DYH2 or D2LIC gene resulted in only a mild phenotype. Both knockout cell lines assembled motile cilia, but the cilia were of more variable lengths and less numerous than wild-type controls. Electron microscopy revealed normally shaped cilia with no swelling and no obvious accumulations of material in the distal ciliary tip. These results demonstrate that dynein-2 contributes to the regulation of ciliary length but is not required for ciliogenesis in Tetrahymena.

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