Ciliate Cells Research Articles

Long-term Studies of Ciliate-Bacterial Interactions: Use of a Chemostat Fed with Bacteria Grown in a Separate Chemostat

Summary: Two-stage chemostat cascades have been used to study growth of the ciliate Tetrahymena pyriformis on Escherichia coli over extended periods of time. Upward drifts (continuous, slow, uni-directional changes) of ciliate number density and downward drifts of ciliate mean cell size and density of residual bacteria occurred for many generations of ciliates before steady states were obtained. Ciliate chemostats were operated at two different dilution rates. Rates of drift were slower, and drifts persisted longer, both in terms of time and in terms of numbers of generations, in the chemostats operated at the higher dilution rate. Some speculations on the origins of the drifts are presented.

The cell cortex during ciliate morphogenesis and ciliogenesis

The cell cortex of a ciliated protozoan contains most of the structure that defines the shape and pattern of the organism. The ciliate cell cortex is composed of both cytoskeletal and membranous components. While the assembly of the cytoskeleton is believed to account for the major part of the development of shape and pattern in this cell (as in all eukaryotic cells), the contribution of membranes to the development of cellular architecture in ciliates is poorly understood. Also, how the cortical membranes are assembled and how this assembly is coordinated with cytoskeletal assembly are virtually unknown. Furthermore, membranes have several unique properties which could be useful in the storage and utilization of blueprints for cellular architecture. Freeze-fracture and freeze-etch electron microscopy provide ways to characterize the molecular architecture and assembly of membranes during development. Efforts are being made to apply these methods to an analysis of morphogenesis and ciliogenesis in Tetrahymena. The results of these studies ar summarized and their possible implications regarding the role of membranes in ciliate morphogenesis are discussed.

Ultrastructure of the gill of the hydrothermal vent bivalveCalyptogena magnifica, with a discussion of its nutrition

Calyptogena magnifica Boss and Turner, 1980, a new Vesicomyidae found during the Galapagos expedition in hydrothermal vents of the East Pacific Rise, was collected in the same Rise at 21°N during the “Oasis” expedition (March 1982), and samples of the gill were fixed for ultrastructural observations. The large size and structure of the gill indicate that this is the organ mainly involved in the nutritional processes ofC. magnifica. Despite the classic structural appearance of the external cilia of its gill, and an obvious production of mucus,C. magnifica is not a filter-feeder, as it does not use filtering processes to provide its major source of nutrition. Negligible particulate transfer is evidenced by reduction of the ciliary groove, of the labial palps and of the digestive tube, as well as by the absence of mucous strings. Histological and ultrastructural observations endorse the hypothesis that endocellular chemoautotrophic bacteria play an important role in the nutrition of the clam. Except for a superficial zone of ciliated cells, most of the gill tissue is comprised of cells which appear to be bacteriocytes, and which are perfectly integrated into the gill tissue and contain abundant and normally reproducing bacteria. The differences observed in the structure of the bacteriocytes suggest a cyclic process of their colonization by bacteria, their possible resorption, and their replacement by new bacteria-infected cells. Energetic substrates (sulfides and organic molecules) are probably directly absorbed by the bacteriocytes through the microvilli of the epithelial cells. Abundant fingerprint-like mitochondria in ciliate cells attest to a particularly high metabolic activity, perhaps related to active biosynthesis.

Methanobacterium formicicum, an endosymbiont of the anaerobic ciliateMetopus striatus McMurrich

The Gram-positive methanogenic endosymbiont of the sapropelic ciliateMetopus striatus was isolated and identified asMethanobacterium formicicum. In the ciliate cell the methanogens are in close association with microbody-like organelles. No mitochondria could be detected. The nature of the microbodies and the physiological background of the observed association are discussed.

Microtubules with more than 13 protofilaments in the dividing nuclei of ciliates.

Microtubules are largely composed of proteins called tubulins. These are stacked in linear arrays called protofilaments (p). Most microtubules have precisely 13p (ref. 1). The 'incomplete' B and C microtubules (10 or 11p) of cilia, flagella, basal bodies and centrioles are widespread exceptions. Very few examples of 'complete' microtubules with more, or less, than 13p have been found. However, the 'ciliate cell' includes a larger number of highly differentiated types of microtubule arrays than most other cell types. The present study was undertaken to ascertain whether there is variation in p number in two ciliates. In both, all complete cytoplasmic microtubules examined have 13p but microtubules with 13-16p are present in the nucleoplasm of dividing nuclei. These features are probably common to ciliates in general because the free-living hymenostone Paramecium tetraurelia and the parasitic heterotrich Nycotherus ovalis are not closely related in terms of taxonomic criteria or life-style.

Photobehaviour of Paramecium bursaria infected with different symbiotic and aposymbiotic species of Chlorella

The endosymbiotic unit of Paramecium bursaria and Chlorella spec. shows two types of photobehaviour: 1) A step-up photophobic response which possibly depends on photosensitive agents in the ciliate cell itself - as is also shown by alga-free Paramecium bursaria - and can be drastically enhanced by photosynthetic activity of symbiotic algae; and 2) a step-down photophobic response. The step-down response leads to photoaccumulation of green paramecia. Both types of photobehaviour in Paramecium bursaria do not depend on any special kind of algal partners: The infection of alga-free Paramecium bursaria with different Chlorella species results in new ciliatealgae-associations. They are formed not only by combination of the original symbiotic algae with their host, but also by infection with other symbiotic or free-living (aposymbiotic) chlorellae, respecitively. Systems with other than the original algae are not permanently stable - algae are lost under stress conditions - but show the same types of photobehaviour. Photoaccumulation in general requires algal photosynthesis and occurs only with ciliates containing more than fifty algae/cell. It is not mediated by a chemotactic response to oxygen in the medium, since it occurs at light fluence rates not sufficient for a release of oxygen by the symbiotic system, e.g., below its photosynthetic compensation point. Photoresponses can be inhibited by 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU). Sensory transduction does not depend on any special symbiotic features of the algae, e.g., sugar excretion. The participation of oxygen in the Paramecium cell, of its cytoplasmic pH and of ions released or taken up by endosymbiotic algae in sensory transduction is discussed.

Factors influencing toxicity of cadmium to Tetrahymena pyriformis: Particulate or soluble form and degree of complexation

The toxicity of cadmium, in the soluble and particulate forms (contaminated bacteria, to Tetrahymena pyriformiis is compared. The toxicity of the metal in the soluble form markedly depends on its degree of chelation. Less complexed forms seem to accumulate more easily in ciliate cells and are the most toxic. Bacteria grown on medium toxified with cadmium contain high concentrations of the metal. The quantity of metal entering protozoa cells when feeding on contaminated bacteria is small and does not produce any toxic effect.

Morphological alterations to the bronchial mucosa in high-dosage long-term exposure to sulfur dioxide.

Light- and electron-microscopic studies were carried out on chronic bronchitis in the rat, produced by high-dosage long-term exposure to sulfur dioxide. Particular attention was given to the advanced stages of the disease. Inflammatory intramural infiltration and fibrosis developed in the regions of the bronchial tree near the hilus and in the peripheral sections. The highly differentiated cells of the bronchial epithelium perish at the same time. After a loss of the goblet and ciliate cells, extensive epithelial metaplasias with dysplasias develop in the central regions of the bronchus. Bronchiolitis obliterans develops in the peripheral regions of the bronchus. In the bronchiolar epithelium, the Clara cells, which play a crucial role in the maintenance of bronchial secretion in the advanced stages of the disease, are preserved.

Chapter 3 Cell Communication, Cell Union, and Initiation of Meiosis in Ciliate Conjugation

This chapter discusses cell communication, cell union, and the initiation of meiosis in ciliate conjugation. For ciliate cells, conjugation is an exceptionally social occasion. During this time, cells of complementary mating types first communicate by mating signals, gain the capacity to unite, and temporarily form bicellular conjugant pairs. In the united cells, a series of nuclear changes, including meiosis, exchange, and fusion of gametic nuclei, is set in motion. Then, the cells separate, returning to their unicellular phase, but developmental changes continue. The fertilization nucleus repeatedly divides mitotically and the division products differentiate into somatic and germ nuclei that eventually replace the pre-existing nuclear system. Certain cortical structures are also reconstructed. Thus, ciliate conjugation encompasses two important features of fertilization— namely, karyogamy and the initiation of development. These processes all commonly occur in fertilization and in related phenomena in many organisms, but some of the characteristics of ciliate conjugation appear to provide unique investigative opportunities. The physical association of cells in conjugation may begin with a subtle contact of cilia, but the association soon becomes more intimate, eventually turning into a tight cell union with cytoplasmic bridges.

A study of nutritional status of Finnish reindeer (Rangifer Tarandus L.) in differents months: I. Composition and volume of the rumen microbiota

The rumen microbiota were studied in free-ranging semi-domestic reindeer in Finnish Lapland under the nutritional conditions obtaining at two different sampling times. Qualitative and quantitative investigations were made of the rumen ciliate fauna and quantitative investigations of the rumen bacterial flora. The volume coefficients for rumen ciliates obtained by Westerling (1970) and that for rumen bacteria obtained by Warner (1962) were used to obtain an indication of the volume of the rumen microbe mass in reindeer. The rumen samples were collected in connection with the round-up and slaughter of reindeer, being taken from 30 animals in December and 29 animals in March. The reindeer slaughtered in December had normal access to food, but those slaughtered in March had grazed on better pastures and received a supplementary feed of hay. The total number of ciliate cells was over six times as high in March as in December, the numbers being 1 182900 and 188 300 per ml rumen contents, respectively. The corresponding total numbers of bacterial cells were 9.65 x 109 in March and 6.65 x 109 in December. The reason for the statistically significantly (P < 0.01) higher numbers in March than in December is probably the better nutritional conditions of the herd slaughtered in March, not the time of the year. The ciliate fauna consisted of 19 different species, although not all the species were found in every sample. The percentage composition of the ciliate fauna did not vary considerably between the two sampling times. The volume of the total microbe mass constituted 8.2% of the rumen contents in March and 1.9 % in December, the average being 5.1 %. The proportion of the ciliate volume in the total microbe mass was clearly higher than that of the bacteria at both sampling times: 7.2 times as high in March and 1.7 times in December, the average being 4.7 times.

Continuous monoxenic culture of Tetrahymena pyriformis.

SUMMARY: A two-stage continuous culture apparatus was used to study the growth and feeding kinetics of the ciliated protozoon Tetrahymena pyriformis GL. The food organism, the bacterium Klebsiella aerogenes, was grown in the first stage using sucrose as the limiting nutrient to establish steady-state populations. By pumping some of this culture to a second fermentor which contained T. pyriformis a continuous supply of K. aerogenes was made available for predation. In the early stages after inoculation the ciliates were few in numbers but large in size, but over a period of a week or two the ciliate cells became smaller and more numerous. The feeding rate of Tetrahymena was found to be dependent upon size and growth rate. The kinetics of feeding and growth were related to the mean volume of the ciliate which increased with dilution rate. It was possible to grow Tetrahymena pyriformis in continuous culture at a rate of 0.38 h.-1 and the maximum specific growth rate was estimated to be 0.43 h.-1, which is almost twice that obtained from batch culture studies. The yield constant of Tetrahymena was 0.54.

Cytomembrane differentiation in a ciliate, Tetrahymena pyriformis. I. Endoplasmic reticulum and dictyosomal equivalents.

Various differentiating forms of rough and smooth endoplasmic reticulum (ER), as well as a novel type of a Golgi apparatus-equivalent organelle, are described for the ciliate Tetrahymena pyriformis. Ergastoplasmic stackings and dictyosomal configurations have been studied in particular detail since such structures had hitherto been reported not to occur in these ciliate cells. A Tetrahymena cell can contain several hundred dictyosomes, which are frequently formed at the mitochondrial jacket-ER. The following way of secretory flow is suggested for Tetrahymena: Small patches of rough ER (or of the nuclear envelope) loose their ribosomes and become smooth. From such smooth membrane areas vesicles pinch off which are distinct by greater membrane thickness and electron contrast as well as by an intimate association with characteristic granulo-fibrillar aggregates. Such ER-derived vesicles can then conflux, either to give rise to a stream of vesicles with distally increasing sizes, or to produce a localized “pile up” as more or less comprehensive stacks of flattened cisternae in the typical mode of a dictyosome with forming and secreting face polarity. The observations indicate that processes of cytomembrane differentiation and membrane flow take place in ciliate systems. In addition, the coincidence of vesicle pinching off with the appearance of fenestrae in the cisternae has led to new concepts of how pores in cisternae might generally be formed as a consequence of vesicle production.

Phytosterols and other lipids as survival factors for Tetrahymena at O-5 C.

SYNOPSIS. Tetrahymena pyriformis syngen 1, mating type II, (optimal growth temperature ∼ 37 C) ordinarily dies out in 5‐14 days at 0‐5 C. Dying cells were lumpy, suggesting membrane damage. By supplying crude soy lecithin, survival at 0‐5 C was prolonged (after growth in peptone‐yeast‐dextrin) to at least 22 weeks. Crude soy sterols or sitosterol or stigmasterol, and antioxidant, e.g., Ionox 330 or ascorbylpalmitate, permitted survival of cells in suspension or in growth media for at least 16‐22 weeks. These sterols are known to protect against triparanol toxicity, which suggested that triparanol, which blocks cholesterol synthesis in higher animals, might enhance cold‐induced injury. Triparanol was more toxic at 0–5 than at 28 C for cell suspensions and cells in growth medium; this toxicity was annulled by crude soy lecithin or β‐sitosterol, the only phytosterol tested. The synthetic medium intended as a control on the crude media became toxic at 0–5 C. Protection against cold damage is discussed as a means of elucidating the role of sterols—especially phytosterols—and other lipids in maintaining the integrity of the ciliate cell membrane.

EVIDENCE FOR A CRYPTOMONAD SYMBIONT IN THE CILIATE, CYCLOTRICHIUM MEUNIERI(1).

Extracts of the marine ciliate Cyclotrichium meunieri contained chlorophylls a and c, carotenoids, and a phycoerythrin with a single absorbance maximum at 542 nm. This assemblage of pigments suggests that the numerous photosynthetic symbionts present in each ciliate cell belong to the Cryptophyceae.