Chilomonas Paramecium Research Articles

First report on ecotoxicological QSTR and i-QSTR modeling for the prediction of acute ecotoxicity of diverse organic chemicals against three protozoan species

The recent years have witnessed an upsurge of interest to assess the toxicity of organic chemicals exhibiting harmful impacts on the environment. In this investigation, we have developed regression-based quantitative structure-toxicity relationship (QSTR) models against three protozoan species (Entosiphon sulcantum, Uronema parduczi, and Chilomonas paramecium) using three sets of descriptor combinations such as ETA indices only, non-ETA descriptors only, and both ETA and non-ETA descriptors to examine the key structural features that determine the toxic properties of protozoa. The interspecies QSTR models (i-QSTRs) were also generated for efficient data gap-filling of toxicity databases. The statistical results of the validated models in terms of both internal and external validation metrics suggested that the models are statistically reliable and robust. Additionally, using these validated models, we screened the DrugBank database containing 11,300 pharmaceuticals for assessing the ecotoxicological properties. The features appearing in the models suggested that non-polar characteristics, electronegativity, hydrogen bonding, π–π, and hydrophobic interactions are responsible for chemical toxicity toward protozoan. The validated models may be utilized for the development of eco-friendly drugs & chemicals, data gap-filling of toxicity databases for regulatory purposes and research, as well as to decrease the use of toxic and hazardous chemicals in the environment.

Relative importance of evolutionary dynamics depends on the composition of microbial predator-prey community.

Community dynamics are often studied in subsets of pairwise interactions. Scaling pairwise interactions back to the community level is, however, problematic because one given interaction might not reflect ecological and evolutionary outcomes of other functionally similar species interactions or capture the emergent eco-evolutionary dynamics arising only in more complex communities. Here we studied this experimentally by exposing Pseudomonas fluorescens SBW25 prey bacterium to four different protist predators (Tetrahymena pyriformis, Tetrahymena vorax, Chilomonas paramecium and Acanthamoeba polyphaga) in all possible single-predator, two-predator and four-predator communities for hundreds of prey generations covering both ecological and evolutionary timescales. We found that only T. pyriformis selected for prey defence in single-predator communities. Although T. pyriformis selection was constrained in the presence of the intraguild predator, T. vorax, T. pyriformis selection led to evolution of specialised prey defence strategies in the presence of C. paramecium or A. polyphaga. At the ecological level, adapted prey populations were phenotypically more diverse, less stable and less productive compared with non-adapted prey populations. These results suggest that predator community composition affects the relative importance of ecological and evolutionary processes and can crucially determine when rapid evolution has the potential to change ecological properties of microbial communities.

Sampling strategy, occurrence and diversity of free-living protozoa in domestic refrigerators

Evaluation of a sampling method to recover free-living protozoa (FLP) from plastic surfaces. Application of the method on different areas inside domestic refrigerators. Plastic coupons seeded with representatives of FLP were swabbed with cotton wools. The recovery efficiency was the highest for Chilomonas paramecium, followed by Tetrahymena pyriformis and the lowest for Acanthamoeba polyphaga. From 43 refrigerators, 19 and 26 were considered FLP positive when sample cultures were incubated at 7°C and 20°C, respectively. The number of FLP-positive cultures was the highest in samples taken from vegetable trays followed by discharge gutters, whereas interior walls were rarely FLP positive. Higher numbers of taxa were observed in enrichment cultures incubated at 20°C instead of 7°C. The combination of microscopy and denaturing gradient gel electrophoresis revealed that discharge gutters occasionally were contaminated with a persistent protozoan population of flagellates (Cercozoa) and amoebae (Tubulinea). The FLP-positive status of refrigerator surfaces was correlated with a high aerobic plate count. The cotton wool sampling method is useful to sample FLP from plastic surfaces. FLP are part of the microbial communities in domestic refrigerators. Knowledge on the occurrence of FLP in food-related indoor environments is scarce. For the first time, a high protozoan diversity in domestic refrigerators is described.

Correlating toxicities of organic compounds to select protozoa using the Abraham model

The Abraham solvation parameter model is used to construct mathematical correlations for describing the nonspecific toxicity of organic compounds to three protozoas (Entosiphon sulcantum, Uronema parduczi and Chilomonas paramecium). The derived mathematical correlations describe the observed published toxicity data to within an overall average standard deviation of approximately 0.35 log units. The correlations can be used to estimate aquatic toxicities of organic chemicals to the three aquatic organisms studied, and to help in identifying compounds whose toxic mode of action might involve chemical specific reactivity, rather than nonpolar or polar narcosis. A principal component analysis of the correlation equations found in this work shows that no water-solvent system we have investigated is a good model for nonspecific aquatic toxicity towards the three protozoas. Furthermore, correlation equations for nonspecific aqueous toxicity towards various biological systems, that we have found in this work and in previous studies, cover such a wide range that no single water-solvent system could ever be a good model for all the biological systems.

Detritus as a potential food source for protozoans: utilization of fine particulate plant detritus by a heterotrophic flagellate, Chilomonas paramecium, and a ciliate, Tetrahymena pyriformis

We investigated the direct utilization of fine particulate detritus (dried and homogenized plant material in the size range of bacteria) as a food source for protozoans using axenic cultures of the cryptomonad, heterotrophic flagellate, Chilomonas paramecium, and the hymenostome ciliate, Tetrahymena pyriformis. When fed media containing only particulate detritus, these species revealed growth rates similar to those reported for field populations. The growth rates of Chilomonas fed exclusively particulate detritus were similar to those obtained on a bacterial diet. Considering the high percentage of detritus particles in the size range of bacteria in lakes, our results imply that direct utilization of detritus by protozoans may form an additional pathway of carbon in aquatic food webs that has generally been overlooked.

Supplementation of the protist Chilomonas paramecium with a highly unsaturated fatty acid enhances its nutritional quality for the rotifer Keratella quadrata

We tested whether a fatty acid supplementation technique using bovine serumalbumin (BSA) as a carrier, previously developed for autotrophic protists, is also appropriate for supplementation of Chilomonas paramecwm-a flagellated heterotrophic protist. Chilomonas paramecium was successfully enriched wth euosapentanoic acid (EPA) and docosahexaenoic acid (DHA), both known to be essential for crustacean zooplankton. Preparing C. paramecium enriched with EPA and DHA in concentrations similar to those found in Cryptomonas phaseolus, an alga known to support high growth and reproduction of Kerafella, allowed us to test the direct nutritional effects of EPA and DHA on population growth and reproduction of the rotifer Keratella quadrata. Growth rates and egg production were highest when K. quadrata was fed with C. phaseolus. Compared to non-supplemented C. paramecium, egg production of K. quadrata was significantly enhanced on a diet of C. paramecium enriched with DHA, whereas no significant effects could be attributed to EPA enrichment. We conclude that DHA is important for reproduction of K. quadrata but cannot explain the majority of the difference in food quality between C. paramecium. and C. phaseolus.

A new culture system for in situ observation of the growth and development of Eucyclops serrulatus (Copepoda: Cyclopoida)

A practical and convenient method of rearing Eucyclops serrulatus in a microculture environment is described. A complete life cycle of E. serrulatus was maintained in a narrow space on a microscope slide glass on which a cover glass of 22 x 40 mm in size was mounted at a height of 0.8 mm. The culture medium was constituted by bottled mineral water boiled with grains of Glycine max (soybean). Chilomonas paramecium, a free-living protozoan organism, was provided as live food. Growth of nauplii hatched from eggs to the first stage of copepodite took an average of 7.7 days, and the growth of copepodite 1 to the egg-bearing adult female took an average of 20.1 days in the microculture cell with an average life time of 44.7 days. Continuous passage of copepods was successfully maintained as long as sufficient medium and food were provided. The microculture method enables an in situ microscopic observation on the growth and developmental process of helminth larvae experimentally infected to copepods as well as of copepod itself. Furthermore, it does not require anesthetization and, therefore, minimize the amount of stress exposed to copepods during the handling process.

Reproductive success of the rotifer Brachionus calyciflorus feeding on ciliates and flagellates of different trophic modes

SUMMARY 1. The nutritional value of the bacterivorous ciliate Tetrahymena pyriformis and the algivorous ciliate Coleps sp., as well as the heterotrophic flagellate Chilomonas paramecium and the autotrophic flagellate Cryptomonas ovata, were investigated in population growth experiments using the rotifer B. calyciflorus. The two ciliates, both flagellates, which were of similar size, shape and mobility, were each offered as a sole diet and as a supplement to the alga Monoraphidium minutum, known to support reproduction of B. calyciflorus.2. To further test nutritional differences between the prey organisms, prey selection experiments were conducted in which B. calyciflorus was able to select between the bacterivorous and algivorous ciliate, and between the heterotrophic and autotrophic flagellate.3. The results demonstrated that both ciliates and the heterotrophic flagellate were not sufficient to support reproduction of B. calyciflorus when offered as a sole diet. They were, however, a good supplement to algal prey (except for the bacterivorous ciliate T. pyriformis). In the prey selection experiments, B. calyciflorus positively selected for the algivorous Coleps sp. and the autotrophic C. ovata.4. Overall, ciliates and heterotrophic flagellates may enhance survival of B. calyciflorus, but reproduction of the rotifer is likely to rely on algal prey. Both higher population growth of B. calyciflorus when fed the algivorous Coleps and the autotrophic Cryptomonas, along with their positive selection, give evidence for prey specific differences in nutrition, with algivorous or autotrophic prey species tending to be of higher nutritional value.

Al3+AND Zn2+-INDUCED STRUCTURAL CHANGES AND LOCALIZATION IN A FULLY-HYDRATED LIVE EUKARYOTIC CELLULAR MODEL

This study combined techniques that did not require preparation protocols that were potentially harmful to the cell, making it possible to investigate cells at, or close to, their natural physiological state. We used the freshwater protozoon Chilomonas paramecium as a eukaryotic cellular model to locate sites of Al3+or Zn2+accumulation and quantify the associated structural changes. Cells were fully hydrated throughout the study, which used a combination of differential interference contrast light microscopy, confocal laser scanning microscopy and transmission X-ray microscopy. The latter technique allowed high resolution (50nm) and high contrast imaging of live cells in solution. For confocal laser scanning microscopy the relatively new fluorochrome Newport Green was used. This made fluorescent complexes with intracellular Al3+and Zn2+, allowing localisation of metal-containing granules and vesicles. After long term exposure a previously unreported annular-shaped site of metal accumulation was found, signifying a vesicle with metal accumulated in the periphery only. After exposure to Al3+and Zn2+, the cell pellicle was thinner and the majority of rounded-up cells had a concentric layering of organelles. By combining a variety of techniques it was possible to gain high resolution structural and chemical information on cells minimally exposed to potentially artefact-inducing procedures.

Fatty acid composition of freshwater heterotrophic flagellates: an experimental study

The fatty acid compositions of 5 freshwater heterotrophic flagellates were studied using laboratory cultures. The flagellates Bodo saltans, Paraphysomonas vestita, Spumella pudica, Poly- toma uvella and Chilomonas paramecium were cultured on Synura medium enriched either with Regilait milk powder (MP medium; Regilait, St Martin Roche, France) or with Tabimin dry fish food (DFF medium; Tetra, Melle, France). The bacteria present in the culture media were also analyzed. The enrichment substrate was found to have a pronounced influence on the fatty acid profiles of the organisms. For example, flagellates grown on the MP medium were characterized by very low con- tents of polyunsaturated fatty acids (PUFA; 1.28 to 5.50% of total fatty acids), whereas those grown on DFF medium contained up to 13.20% PUFA. Irrespective of the species studied, the dominant PUFA were those of the (n-6) series. The presence of branched uneven-numbered fatty acids and of 18:1(n-7) within the protozoans reflects an intensive bacterivorous activity that is understandable in phagotrophic species such as B. saltans, P. vestita and S. pudica but is debatable in C. paramecium and P. uvella, as these species have been described as osmotrophic. The heterotrophic flagellates in this study seemed to have varying, but rather limited, capacities of PUFA biosynthesis and biocon- version that were partly related to the physicochemical conditions in the cultures (temperature and dissolved oxygen) and to the phylogenetic relations of the organisms. Species containing a leucoplast or a residual plastid reproduced in a very attenuated manner the characteristic PUFA profiles of autotrophic flagellates belonging to their taxonomic group. This was mainly the case for C. parame- cium and P. uvella. Finally, our results suggest that in the natural environment, the PUFA contents of picoplanktonic prey and of dissolved organic matter are the main factors influencing the PUFA con- tent of these flagellates.

Laboratory maintenance of Eucyclops serrulatus (Copepoda: Cyclopoida)

A simple method for culturing a freshwater copepod Eucyclops serrulatus is described. A flagellate Chilomonas paramecium serves as the food organism. Starting from a single, egg-bearing female collected in a pond, the copepod proliferated for at least 10 generations apparently with no adverse changes. The stock culture has been maintained with minimal effort for at least 19 months. The method is expected to make the copepod useful in the laboratory as an intermediate host of various parasitic helminths.

Structural changes in fully hydrated Chilomonas Paramecium exposed to copper

Summary The aim of this study was to determine structural changes induced by the free copper ion in fully hydrated cells of the flagellate protozoon Chilomonas paramecium , a common inhabitant of polluted waters, and often exposed to fluctuating levels of external metals. Light microscopy showed that C. Paramecium was sensitive to copper; the cells rounded up within minutes of exposure to 2.5 mg/1 copper, and were almost spherical within 20 minutes. However, they were able to tolerate the increased copper level, and remained in this altered state for weeks. Soft X-ray microscopy showed that compartments formed and ejectosomes were released in response to initial copper exposure. All cells exposed for 28 hours had a posteriorly positioned indentation that could not be correlated to the vestibulum. Some cells had regenerated their flagella. Quantified data pertaining to changes in the pellicle width after copper exposure of live, fully hydrated cells with natural specimen contrast are given.

Effects of Basal Resources, Predation, and Alternative Prey in Microcosm Food Chains

Ecological theorists propose that the species composition of trophic levels can influence the relative strengths of top—down (predation) or bottom—up (nutrient) effects in food chain. We tested this by constructing two— and three—level food chains of bacteria and protists. Bacteria made up to first trophic level. The second level contained Chilomonas paramecium alone, Colpidium cf. striatum alone, or both together. Predatory Euplotes patella occupied the third trophic level. These assemblages were cultured in microcosms containing either low— or high—nutrient medium. Manipulating nutrients and predation produced comparable changes in the abundance of bacteria. In the second trophic level, Chilomonas was usually driven extinct by predation, but Colpidium was affected more by nutrients than predation because it had a partial size refuge from predation. Both species survived more poorly with predatory Euplotes if the other was present, because the predator was more abundant and persistent when both prey were available. The predator was less persistent in high—nutrient microcosms, because additional nutrients boosted the proportion of Colpidium populations within the size refuge. This type of mechanism could limit trophic cascades in food chains where resources affect prey vulnerability.

Chimeric conundra: are nucleomorphs and chromists monophyletic or polyphyletic?

All algae with chloroplasts located not freely in the cytosol, but inside two extra membranes, probably arose chimerically by the permanent fusion of two different eukaryote cells: a protozoan host and a eukaryotic algal symbiont. Two such groups, cryptomonads (phylum Cryptista) and Chlorarachniophyta, still retain a DNA-containing relic of the nucleus of the algal endosymbiont, known as the nucleomorph, as well as the host nucleus. These two phyla were traditionally assumed to have obtained their chloroplasts separately by two independent symbioses. We have sequenced the nuclear and the nucleomorph 18S rRNA genes of the nonphotosynthetic cryptomonad Chilomonas paramecium. Our phylogenetic analysis suggests that cryptomonad and chlorarachniophyte nucleomorphs may be related to each other and raises the possibility that both phyla may have diverged from a common ancestral chimeric cell that originated by a single endosymbiosis involving an algal endosymbiont related to the ancestor of red algae. But, because of the instability of the molecular trees when different taxa are added, there is insufficient evidence to overturn the traditional view that Chlorarachnion nucleomorphs evolved separately from a relative of green algae. The four phyla that contain chromophyte algae (those with chlorophyll c--i.e., Cryptista, Heterokonta, Haptophyta, Dinozoa) are distantly related to each other and to Chlorarachniophyta on our trees. However, all of the photosynthetic taxa within each of these four phyla radiate from each other very substantially after the radiation of the four phyla themselves. This favors the view that the common ancestor of these four phyla was not photosynthetic and that chloroplasts were implanted separately into each much more recently. This probable polyphyly of the chromophyte algae, if confirmed, would make it desirable to treat Cryptista, Heterokonta, and Haptophyta as separate kingdoms, rather than to group them together in the single kingdom Chromista.

Factors Affecting the Salinity Tolerance of the Freshwater Cryptomonad Chilomonas paramecium

ABSTRACT. The capacity of the freshwater cryptomonad Chilomonas paramecium to develop a tolerance for seawater in the growth medium was investigated as part of a research program exploring potential microbial food sources for estuarine bivalve mollusks. By gradually increasing the percentage of estuarine seawater included in a freshwater culture medium over the course of 10 years, strains were obtained that tolerate from 16 to 32% seawater (highest salinity 10.5 ppt), achieving equivalent final densities with similar gross biochemical composition. However, after subculture in seawater‐containing media for over 20 years, growth rates in more‐saline media remained appreciably slower than in low‐salinity media. Reduction of C. paramecium growth rate by seawater was found to be exacerbated in media with an initial pH of 3.5 as compared with pH 4.0–5.0, suggesting either a specific H+ effect upon metabolism of the medium carbon source (lactic acid) or a general cation effect upon nutrient uptake or cell metabolism. By contrast, depression of growth rates at high salinity was ameliorated by eliminating sodium‐phosphate enrichments in growth media. This suggests that cations in the phosphate salt were contributing to cation‐mediated growth inhibition. Results indicate a potential for C. paramecium, cultured in moderately saline media with no phosphate enrichments, to be used as a carbohydrate supplement for laboratory and hatchery feeding of estuarine bivalve mollusks.

Ultrastructure of Chilomonas paramecium and the phylogeny of the cryptoprotists

The ultrastructure of the cryptoprotist Chilomonas paramecium is reviewed and compared to earlier accounts. Distinctive features include a complex cytoskeleton which defines the cell organization and interconnects cell components; trichocysts which resemble those in other cryptoprotists; and two non-photosynthetic plastids. During mitosis there is partial dispersal of the nuclear envelope early in prophase but some remains at the nuclear periphery throughout mitosis. At metaphase chromosomes are arrranged on the longitudinal axis of an elgonated elliptical nucleus. During telophase the chromosomes decondense and the nuclear envelope reforms. Cell structure is compared with that in other cryptoprotists, and origin of this taxon of algae is discussed.

AN ULTRASTRUCTURAL SURVEY OF CRYPTOMONAD PERIPLASTS USING QUICK‐FREEZING FREEZE FRACTURE TECHNIQUES1

ABSTRACTA quick‐freezing technique for freeze fracturing was used to determine periplast plate types in 20 cryptomonads. With this technique cells are frozen so rapidly that major artifacts are eliminated. We propose that periplast plates are attached to the cell membrane by intramembrane particles (IMP's), consequently plate shapes are outlined by IMP distribution in fractured membranes. Round to oval, sometimes slightly angular, plates occur in Cryptomonas ovata, Cryptomonas tetrapyrenoidosa, Cryptomonas parapyrenoidifera, Cryptomonas obovata, Cryptomonas erosa and two unidentified species of Cryptomonas; large rectangular plates occur in Chroomonas pochmannii, Chroomonas coerulea and Hemiselmis sp.; small rectangular plates were found in Cryptomonas sp. (Strain SDB); square to slightly rounded plates occur in Cryptomonas chrysoidea and a single continuous plate or sheet, perforated by ejectisome pores, was observed in Cryptomonas caudata, Cryptomonas rostratiformis, Cryptomonas marssonii, Cryptomonas platyuris, Cryptomonas curvata, Cryptomonas ozolini, Chilomonas paramecium and Rhodomonas sp. Oval and square plates are described for the first time in Cryptomonas. Plate IMP's may be morphologically modified in size and shape, depending upon their location in relation to the plate, the plate ridges, and ejectisome chambers. Conformational changes in plate shapes, to form hexagons or polygons, may be induced when cells are subjected to fixation, desiccation, cryoprotectants or centrifugation.

The ejectisomes of the flagellate Chilomonas paramecium: visualization by freeze-fracture and isolation techniques.

Freeze-fracture procedures were used to visualize ejectisomes and adjacent plasma membrane specializations in the flagellate protozoan Chilomonas paramecium. The ejectisomes are membrane-bounded, cylindrically rolled, extrusive organelles. Small ones occur in large number beneath the plasma membrane of the body and considerably larger ones are located around the gullet membrane. The intra-membrane particle distribution is different in each type. In small ejectisomes, the portion of the membrane in contact with the plasma membrane of the body has a P-face rosette of five particles while the plasma membrane has not been observed with a rosette. Small ejectisomes and plasma membrane both contain aggregations of particles a short distance from the contact or docking site. Slightly beneath the plasma membrane is the periplastic sheet with which we speculate the small ejectisomes interact during the docking phenomenon. No obvious rosettes have been observed in large ejectisomes. Some other ejectisomal structures are presented and discussed.

Comparison of the flagellar rootlets and periplast in two marine cryptomonads

The flagellar rootlets and the cytoskeletal structures of the furrow–gullet region are described for two marine species of Cryptomonas. The rootlets of the two species are very similar, but are more reduced in C. sp. θ than in C. sp. [Formula: see text]. Four rootlets are present: a compound rootlet made up of a striated component of 60- to 80-nm periodicity overlain by three microtubules which extends anteriorly into the left lobe of the cell, a rhizostyle which descends to the nucleus and the posterior end of the cell, an ascending microtubular rootlet which passes anteriorly into the right lobe of the cell, and a lateral microtubular rootlet which curves around the dorsal side of the contractile vacuole. In C. sp. [Formula: see text], the rhizostyle consists of four winged microtubules; in C. sp.θ, it is reduced to three microtubules which lack wings. In C. sp.[Formula: see text], the ascending rootlet consists of five microtubules; in C. sp. θ, of three microtubules. In C. sp. θ, the lateral rootlet is reduced to a very short remnant. The rootlet systems of these two photosynthetic cryptomonads are similar to, but much reduced in complexity from, that of the leucoplast-containing cryptomonad Chilomonas paramecium. In the vestibulum and furrow–gullet region, the characteristic periplast plates are replaced by a modified periplast in C. sp. θ and a striated rim fiber in C. sp. [Formula: see text].

The nucleotide sequence of 5 S ribosomal RNA from a protozoan species Chilomonas paramecium belonging to the class Phytomastigophorea

In the protozoan class Phytomastigophorea, the 5 S rRNA sequences from three species, Crypthecodinium cohnii (order Dinoflagellida), Euglena gracilis (order Euglenida) and Chlamydomonas reinhardii (order Volvocida), are known. These 5 S rRNAs do not show any striking similarity to each other, suggesting that these orders, although classified in the same class Phytomastigophorea, are only remotely related to each other. Here, we have determined the sequence of 5 S rRNA of another Phytomastigophorea species, Chilomonas paramecium (order Cryptomonadida), and compared it to those of the other species of the same class as well as of other eukaryotes to deduce the phylogenie position of Chilomonus. The Chilomonas sequence shows a fairly low but almost equal similarity to the sequences of the other Phytomastigophorea species and also to those of other protozoa, plants, fungi and animals.