Paramecium

A variety of chemicals including foaming agents are used to aid in the protection of forest resources from the wild land fires. The fire-fighting foams (FFFs) are formulations composed principally of surfactants. As a part of Japanese national project, environmentally inert FFFs have been developed. There is an emerging need for testing the impacts of these FFFs on the living organisms composing the typical landscapes or ecosystems in Japan. In the present report, we aimed to describe our latest attempt for assessing both the short-tem and long-term impacts of FFFs in aquatic (fresh water) and semi-aquatic (wetland) ecosystems , by employing the laboratory-sized model assays (preliminary studies) and the biotope-based observation, respectively. In the biotope assays which was based on the observation in compact biotopes mimicking the fresh water environments and wetland, both the acute and long-term eco-toxic impacts of two FFFs (soap-based and synthetic detergent-based) were assessed. Spraying of synthetic detergent-based foam formula was shown to be more toxic compared to soap-based formula and mock water treatment.

Paramecium bursaria is an unicellular organism that lives widely in fresh water environments such as rivers and ponds. Recent studies have suggested that in vivo cellular robotics using the cells of P. bursaria as micro-machines controllable under electrical and optical stimuli, has a variety of engineering applications such as transport of micro-sized particles in the capillary systems. The present study aimed to test if the swimming cells of P. bursaria, implementable in capillaries or on chips, are applicable for detection of metal ions. For model assays, rare earth elements (REEs) were chosen as target chemicals. In P. bursaria, LC 50 values for REE ions ranged between 2.0 and 62.7 µM. Among them, Sc was shown to be most toxic. In addition to the lethal impacts of REE ions, most of REE ions at sub-lethal concentrations at around 10-30 µM, showed inhibitory action against the motility of the cells during the electrically forced motility known as galvanotaxisis. In conclusion, in the non-lethal ranges of REE concentration, swimming cells of P. bursaria report the presence of REE ions, by lowering the motility.

Population-genomic analyses are essential to understanding factors shaping genomic variation and lineage-specific sequence constraints. The dearth of such analyses for unicellular eukaryotes prompted us to assess genomic variation in Paramecium, one of the most well-studied ciliate genera. The Paramecium aurelia complex consists of ∼15 morphologically indistinguishable species that diverged subsequent to two rounds of whole-genome duplications (WGDs, as long as 320 MYA) and possess extremely streamlined genomes. We examine patterns of both nuclear and mitochondrial polymorphism, by sequencing whole genomes of 10-13 worldwide isolates of each of three species belonging to the P. aurelia complex: P. tetraurelia, P. biaurelia, P. sexaurelia, as well as two outgroup species that do not share the WGDs: P. caudatum and P. multimicronucleatum. An apparent absence of global geographic population structure suggests continuous or recent dispersal of Paramecium over long distances. Intergenic ...

Two types of polymeric post-translational modifications of alpha/beta-tubulin, glycylation and glutamylation, occur widely in cilia and flagella. Their respective cellular functions are poorly understood. Mass spectrometry and immunoblotting showed that two closely related species, the ciliates Tetrahymena and Paramecium, have dramatically different compositions of tubulin post-translational modifications in structurally identical axonemes. Whereas the axonemal tubulin of Paramecium is highly glycylated and has a very low glutamylation content, the axonemal tubulin of Tetrahymena is glycylated and extensively glutamylated. In addition, only the alpha-tubulin of Tetrahymena undergoes detyrosination. Mutations of the known glycylation sites in Tetrahymena tubulin affected the level of each polymeric modification type in both the mutated and nonmutated subunits, revealing cross-talk between alpha- and beta-tubulin. Ultrastructural analyses of glycylation site mutants uncovered defects in the doublet B-subfiber of axonemes and revealed an accumulation of dense material in the ciliary matrix, reminiscent of intraflagellar transport particles seen by others in Chlamydomonas. We propose that polyglycylation and/or polyglutamylation stabilize the B-subfiber of outer doublets and regulate the intraflagellar transport.

The effect of euplotin C—a cytotoxic secondary metabolite produced by the protist ciliate Euplotes crassus—on the voltage-dependent Ca2+ channel activity was studied in a single-celled system by analyzing the swimming behavior of Paramecium. When the intraciliary Ca2+ concentration associated with plasma membrane depolarization increases, a reversal in the direction of ciliary beating occurs, and consequently the swimming direction changes. The ciliary reversal duration is correlated with the amount of Ca2+ influx. The present study demonstrates that the duration of continuous ciliary reversal (CCR), triggered by high external KCl concentrations, is longer in euplotin C-treated cells. Using selective Ca2+ channel blockers, we demonstrate that euplotin C modulates Ca2+ channels similar to the T- and L-types that occur in mammalian cells. Indeed, the increase of CCR duration significantly decreased when flunarizine and nimodipine-verapamil blockers were employed. Membrane fluidity measurements using a fluorescent dye, 6-lauroyl-2-dimethylaminonaphtalene (laurdan), indicated that membranes in euplotin C-treated cells are more tightly packed and ordered than membranes in control cells. Our data suggest that euplotin C enhances backward swimming in our unicellular model system by interacting with the ciliary Ca2+ channel functions through the reduction of cell membrane fluidity.

In the past 10 years, the number of endosymbionts described within the bacterial order Rickettsiales has constantly grown. Since 2006, 18 novel Rickettsiales genera inhabiting protists, such as ciliates and amoebae, have been described. In this work, we characterize two novel bacterial endosymbionts from Paramecium collected near Bloomington, IN. Both endosymbiotic species inhabit the cytoplasm of the same host. The Gram-negative bacterium “ Candidatus Bealeia paramacronuclearis” occurs in clumps and is frequently associated with the host macronucleus. With its electron-dense cytoplasm and a distinct halo surrounding the cell, it is easily distinguishable from the second smaller symbiont, “ Candidatus Fokinia cryptica,” whose cytoplasm is electron lucid, lacks a halo, and is always surrounded by a symbiontophorous vacuole. For molecular characterization, the small-subunit rRNA genes were sequenced and used for taxonomic assignment as well as the design of species-specific oligonucle...

The quinalphos metabolite 2-hydroxyquinoxaline (HQO), previously shown to photocatalytically destroy antioxidant vitamins and biogenic amines in vitro, was tested for toxicity in several small aquatic organisms and for mutagenicity in Salmonella typhimurium. In the rotifer Philodina acuticornis, HQO caused the disappearance of large individuals and increased hydroperoxide concentration. The latter effect was not only observed in animals kept in a light/dark cycle, but also in constant darkness, indicating that HQO can assume a reactive state and/or form reactive intermediates under the influence of either light or redox-active metabolites, in particular, free radicals. Cell proliferation was inhibited in the ciliate Paramecium bursaria. In the dinoflagellate Lingulodinium polyedrum, which allows early detection of cellular stress on the basis of bioluminescence measurements, strong rises in light emission became apparent on the 2nd day of exposure to HQO and continued until cells died between 12 and 18 days of treatment. Oxidative damage of protein by HQO was demonstrated by measuring protein carbonyl in L. polyedrumin vivo as well as in light-exposed bovine serum albumin in vitro. In an Ames test of mutagenicity, HQO proved to be genotoxic in both light- and dark-exposed bacteria. HQO appears as a source of secondary quinalphos toxicity, which deserves further attention. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 33–43, 2007.

In vivo K(+), Na(+), Ca(2+) and Cl(-) activities in the cytosol and the contractile vacuole fluid of Paramecium multimicronucleatum were determined in cells adapted to a number of external osmolarities and ionic conditions by using ion-selective microelectrodes. It was found that: (1) under standardized saline conditions K(+) and Cl(-) were the major osmolytes in both the cytosol and the contractile vacuole fluid; and (2) the osmolarity of the contractile vacuole fluid, determined from K(+) and Cl(-) activities only, was always more than 1.5 times higher than that of the cytosol. These findings indicate that excess cytosolic water crosses the contractile vacuole complex membrane osmotically. Substitution of choline or Ca(2+) for K(+) in the external solution or the external application of furosemide caused concomitant decreases in the cytosolic K(+) and Cl(-) activities that were accompanied by a decrease in the water segregation activity of the contractile vacuole complex. This imp...

The yeast community was studied in a municipal full-scale membrane bioreactor wastewater treatment plant (MBR-WWTP). The unexpectedly high diversity of yeasts indicated that the activated sludge formed a suitable environment for them to proliferate, with cellular concentrations of 2.2 ± 0.8 × 10(3) CFU ml(-1). Sixteen species of seven genera were present in the biological reactor, with Ascomycetes being the most prevalent group (93%). Most isolates were able to grow in a synthetic wastewater medium, adhere to polyethylene surfaces, and develop biofilms of variable complexity. The relationship between yeast populations and the protists in the MBR-WWTP was also studied, revealing that some protist species preyed on and ingested yeasts. These results suggest that yeast populations may play a role in the food web of a WWTP and, to some extent, contribute to membrane biofouling in MBR systems.

In vivo labeling of Paramecium cells with 32Pi most heavily labels a minor 63-kDa protein that undergoes a rapid, Ca2+-dependent dephosphorylation when the cell is stimulated to release. This stimulus-sensitive phosphoprotein was isolated and purified to apparent homogeneity. A polyclonal affinity purified antibody made against the purified protein recognizes both the phosphorylated and dephosphorylated forms of the protein. The phosphorylated 63-kDa protein is found in the cytosolic fraction; it is slightly acidic with two isoelectric forms at pI 5.8 and 6.2 and probably exists as a monomeric 60-65-kDa polypeptide in the native state. The labeled phosphoamino acid of the protein is phosphoserine. The affinity purified antibody recognizes a third isoelectric form at pI 6.3 that appears unlabeled. The specificity of the antibody was confirmed by showing that it immunoprecipitates the correct protein, i.e. the stimulus-sensitive 63-kDa phosphoprotein. The availability of purified 63-k...