New, world-wide data on the distribution of species of the Paramecium aurelia complex (Ciliophora, Protozoa)

This is the first report on the presence of P. biaurelia in Tasmania, an island that has probably never been investigated before for the occurrence of the P. aurelia species. P. tetraurelia was recorded in Brazil, another very poorly investigated country in terms of this species complex. New stands of P. biaurelia and P. tetraurelia were also recorded in Japan. We present data concerning the occurrence and distribution of the P. aurelia species on different continents as a background for the newly described stands of P. aurelia spp.     

Species of the Paramecium aurelia complex (Protozoa, Ciliophora) in the Middle Sudetes of Poland

Four species of the Paramecium aurelia complex were found in the studied territory (Klodzko Basin) of the Middle Sudetes in Poland, i.e. Paramecium primaurelia, P. biaurelia, P. tetraurelia and P. novaurelia . Of these, P. biaurelia and P. novaurelia appeared with greater frequency than P. primaurelia . Both species dominated over P. primaurelia in the number of determined habitats, as well as in the number of examined clones. Paramecium tetraurelia was rare in the area, being found in only one habitat.     

Variable telomeric repeat synthesis in Paramecium tetraurelia is consistent with misincorporation by telomerase.

Telomeric DNA at the ends of chromosomes consist of short, tandem repeat sequences. The telomeres of Paramecium tetraurelia are made up of variable repeats, whereas Paramecium caudatum telomeric repeats are largely invariant. To investigate variable repeat synthesis in P. tetraurelia, mutated telomerase RNA genes were expressed in vivo. We demonstrate that the P. caudatum telomerase RNA can participate in telomere synthesis when expressed in the P. tetraurelia macronucleus, despite 24% primary sequence divergence of the RNAs between the two species. De novo telomeric repeats from transformants indicate that P. tetraurelia telomerase fidelity is dramatically affected by template substitutions and that misincorporation at a single templating position is likely to account for the majority of P. tetraurelia telomeric DNA variability. Furthermore, we show that fidelity is not solely a function of the RNA moiety, as the P. caudatum telomerase RNA does not impart high fidelity to the chimeric enzyme.     

Recent data on the occurrence of species of the Paramecium aurelia complex in Europe

Among 15 species of the Paramecium aurelia complex known world-wide, 10 have been found in Europe, namely: P. primaurelia, P. biaurelia, P. triaurelia, P. tetraurelia, P. pentaurelia, P. sexaurelia, P. septaurelia, P. novaurelia, P. dodecaurelia, and P. tredecaurelia. Recent data on the frequency of occurrence of the species in Europe are given in the paper.     

Relationships of species of the Paramecium aurelia complex (Protozoa, Ph. Ciliophora, Cl. Oligohymenophorea) based on sequences of the histone H4 gene fragment

A fragment ofhistone H4 gene (160 bp long) was sequenced in the standard strains of P. primaurelia (DQ067620), P. biaurelia (DQ067621), P. tetraurelia (DQ067622), P. pentaurelia (DQ067623), P. septaurelia (DQ067624), P. octaurelia (DQ067625), P. decaurelia (DQ067626), P. undecaurelia (DQ067627), P. dodecaurelia (DQ067628), P. tredecaurelia (DQ067629), and P. quadecaurelia (DQ067630). The tree constructed according to the Kimura model presents two main species clusters, one comprising P. undecaurelia, P. octaurelia, P. septaurelia, and the second cluster with P. pentaurelia, P. tredecaurelia, P. quadecaurelia, P. tetraurelia, P. decaurelia, P. primaurelia, P. biaurelia. P. dodecaurelia was recovered as a separate branch. The tree constructed on the basis of the maximum likelihood method also presents two species clusters, one with P. undecaurelia, P. octaurelia, P. septaurelia, and the second with P. primaurelia, P. decaurelia, P. pentaurelia, P. tredecaurelia, P. quadecaurelia, P. tetraurelia. P. biaurelia forms a basal clade to the latter cluster, and P. dodecaurelia was recovered as a clearly distinct branch from the clusters.     

Intraspecies Variability in the Esterases and Acid Phosphatases of Four Species of the Paramecium aurelia Complex1

ABSTRACT. One hundred eighty-eight stocks of Paramecium primaurelia. P. biaurelia, P. tetraurelia. and P. octaurelia were grown axenically and screened for variation in four different esterases and acid phosphatase using starch gel electrophoresis. Major observations: frequency of intraspecies variation for these enzymes is much lower in these four species than in other organisms; hypervariability for two esterases occurs in P. biaurelia both in isolates from worldwide locales and in a restricted locale; clustering of variations occurs in a high proportion of variant stocks in all four species; frequency of intraspecies variation is highest in Central and South America for all four species; and geographical differentiation is lacking between stocks in the same species both for common as well as variant phenotypes despite the cosmopolitan distribution of these species. These results are not correlated with adaptations that favor inbreeding over outbreeding. nor is the possession of bacterial endosymbionts strongly correlated with enzyme variation. When the riequency of intraspecies variation was examined for the aurelia complex of species as a whole for 13 enzymes, mitochondrial DNA, and ribosomal DNA, differences between enzymes in frequency of variation could be seen, ranging from less than 2% for seven enzymes to 12.4% for glucosephosphate isomerase, a value similar to that observed for malic dehydrogenase, mitochondrial DNA, and ribosomal DNA in P. tetraurelia. The percentage of polymorphic enzyme loci in the complex as a whole was found to be much lower than that observed for other organisms. For the species more intensely studied in this paper the level of genetic polymorphism was also much lower, although P. biaurelia showed greater variability for two of the enzymes.     

The glyceryl ethers of Paramecium phospholipids and phosphonolipids

Two glyceryl ethers, 1-O-hexadecyl glycerol and 1-O-cis-octadec-11-enyl glycerol, chimyl and paramecyl alcohol, respectively, were quantified in total phospholipids and five glycerophospholipid classes from cells and cilia of the ciliated protozoon, Paramecium tetraurelia. The ether content of 2-aminoethyl phosphonoglycerolipid was 85-90 mole %. Concentrations of ethers were greatest in the ethanolamine phosphonolipids greater than phosphatidylcholines greater than phosphatidylserines greater than phosphatidylethanolamines greater than phosphatidylinositols. The glyceryl ether concentrations in total cellular phospholipids increased with culture age in P. tetraurelia and P. multimicronucleatum cells. The glyceryl ether concentrations in the phospholipids of P. tetraurelia cilia remained constant from mid log to stationary phase of culture growth. Paramecium tetraurelia phospholipid glyceryl ether concentrations were made greater by supplementation of cultures with chimyl alcohol.     

Effects of mutagens on the clonal lifespan of Paramecium tetraurelia.

There has been interest in the phenomenon that a cell cannot undergo unlimited reproduction under adequate conditions and undergoes senescence. In holotrichous ciliates, Paramecium has a limit of vegetative reproduction without sexual reproduction but Tetrahymena does not always have a limited lifespan. Comparing the two species would increase our knowledge of the mechanism of cellular clonal aging. We previously showed that mutations induced by X-rays shorten clonal lifespan. In this study, we examined whether mutagens shorten the clonal lifespan of Paramecium tetraurelia. P. tetraurelia was exposed to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 0.045 mg/ml, for 30 min. The animal was exposed to MNNG 6 times in total while young (under 80 divisions from the start of a clonal life cycle) or 4 times during the senescent stage. MNNG shortened the clonal lifespan as expressed by the decrease in fission number from 186 +/- 55 (4 cell lines) to 136 +/- 21 (6 cell lines) with the first two treatments but with further exposures the lifespan increased to 182 +/- 15 (5 cell lines). MNNG had no effect when administered at the older age. Exposure of P. tetraurelia to 4-nitroquinoline-N-oxide at 0.021 mg/ml twice for 12 and 15 min at the younger age reduced the mean clonal lifespan from 143 +/- 28 to 125 +/- 21 and the maximum lifespan from 263 +/- 33 to 175 +/- 25.     

Induction of Conjugation by Methyl Cellulose in Paramecium

ABSTRACT An improved method has been developed for the induction of selfing conjugation in Paramecium. Methyl cellulose induces selfing conjugation simply and efficiently in all species examined. Induction of conjugation by methyl cellulose was characterized in P. caudatum , where it occurred only in sexually mature, mating reactive cells. Conjugation produced sexual offspring and the time course of nuclear processes was substantially the same as that in natural conjugation between cells of complementary mating types. The method is useful for genetic studies in a wide variety of Paramecium species including P. caudatum, P. tetraurelia, P. multimicronucleatum and P. bursaria.     

Resource specialization determines whether history influences community structure

History, specifically the sequence of species arrival, can affect community composition. Tests for a locally operating mechanism that can produce this result remain rare. Here we show how interspecific competition for resources combined with history can produce different communities. Specifically, history should influence community structure much less when all competitors use the same resource base than when some resources are unavailable to some competitors. We manipulated the resources available to competing ciliates in aquatic microcosms to test this hypothesis. We created communities that had only bacteria, or both bacteria and algae as consumable resources. When only bacteria were available, the best competitor, Colpidium striatum , always dominated regardless of differences in colonization history. History did affect the densities of competitively equivalent subordinate species, Paramecium tetraurelia and P. caudatum . The least effective competitor, Tetrahymena thermophila , went extinct in almost every community. P. tetraurelia and P. caudatum can also consume algae in addition to bacteria. History had a much larger effect in communities where both bacteria and algae were available as resources. In these communities, the initially dominant species always maintained dominance throughout the experiment, with the exception of T. thermophila which still went extinct. The experiment lasted for over 30 generations of the dominant species, so all effects of history persisted over ecologically important time scales.     

Further investigations on the zooplankton of water bodies in the Botanical Garden of the Jagiellonian University in Kraków

The aim of this study was to register the zooplanktonic organisms in water bodies in the Botanical Garden of the Jagiellonian University in Kraków, especially from the point of view of the occurrence of species of the Paramecium aurelia complex. In one pond, artificially constructed, the presence of P. tetraurelia was revealed.     

Phylogenetic relationships of the genus Paramecium inferred from small subunit rRNA gene sequences

The genus Paramecium includes species that are well known and very common in freshwater environments. Species of Paramecium are morphologically divided into two distinct groups: the "bursaria" subgroup (foot-shaped) and the "aurelia" subgroup (cigar-shaped). Their placement within the class Oligohymenophorea has been supported by the analysis of the small subunit rRNA gene sequence of P. tetraurelia. To confirm the stability of this placement and to resolve relationships within the genus, small subunit rRNA gene sequences of P. bursaria, P. calkinsi, P. duboscqui, P. jenningsi, P. nephridiatum, P. primaurelia, and P. polycaryum were determined and aligned. Trees constructed using distance-matrix, maximum-likelihood, and maximum-parsimony methods all depicted the genus as a monophyletic group, clustering with the other oligohymenophorean taxa. Within the Paramecium clade, P. bursaria branches basal to the other species, although the remaining species of the morphologically defined "bursaria" subgroup do not group with P. bursaria, nor do they form a monophyletic subgroup. However, the species of the "aurelia" subgroup are closely related and strongly supported as a monophyletic group.     

Isolation and expression of two genes encoding eukaryotic release factor 1 from Paramecium tetraurelia

Paramecium tetraurelia, like some other ciliate species, uses an alternative nuclear genetic code where UAA and UAG are translated as glutamine and UGA is the only stop codon. It has been postulated that the use of stop codons as sense codons is dependent on the presence of specific tRNAs and on modification of eukaryotic release factor one (eRF1), a factor involved in stop codon recognition during translation termination. We describe here the isolation and characterisation of two genes, eRF1-a and eRF1 b, coding for eRF1 in P. tetraurelia. The two genes are very similar, both in genomic organization and in sequence, and might result from a recent duplication event. The two coding sequences are 1,314 nucleotides long, and encode two putative proteins of 437 amino acids with 98.5% identity. Interestingly, when compared with the eRF1 sequences either of ciliates having the same variant genetic code, or of other eukaryotes, the eRF1 of P. tetraurelia exhibits significant differences in the N-terminal region, which is thought to interact with stop codons. We discuss here the consequences of these changes in the light of recent models proposed to explain the mechanism of stop codon recognition in eukaryotes. Besides, analysis of the expression of the two genes by Northern blotting and primer extension reveals that these genes exhibit a differential expression during vegetative growth and autogamy.     

Factors Determining the Frequency of the Killer Trait within Populations of the Paramecium aurelia Complex

The factors maintaining the cytoplasmically inherited killer trait in populations of Paramecium tetraurelia and Paramecium biaurelia were examined using, in part, computer simulation. Frequency of the K and k alleles, infection and loss of the endosymbionts, recombination during conjugation and autogamy, cytoplasmic exchange and natural selection were incorporated in a model. Infection during cytoplasmic exchange at conjugation and natural selection were factors that would increase the proportion of killers in a population. Conversely, k alleles reduced the proportion of killers in a population, acting through conjugation and autogamy. Field studies indicate that the odd mating type is prevalent in P. tetraurelia isolated from nature. Conjugation and therefore transmission by cytoplasmic transfer would be rare. Competition studies indicate a strong selective disadvantage for sensitives at concentrations found in nature. Natural selection must therefore be the factor maintaining the killer trait in P. tetraurelia.     

Species of the Paramecium aurelia complex in Japan.

In Japan, the presence of Paramecium sexaurelia was revealed for the first time, and a new habitat of P. tetraurelia was found there.     

Interspecies Relationships in the Paramecium aurelia Complex: Acid Phosphatase Variation1

ABSTRACT. Up to five zones of acid phosphatase activity appear in gels after electrophoresis of detergent-treated extracts from 13 of the 14 species of the Paramecium aurelia complex. The overall pattern is somewhat similar for all species: differences in intensity and mobility of individual zones permit the grouping of these sibling species into eight groups. All 14 species can be identified using the procedure of enzyme electrophoresis, although two of them are more similar than is usually the case. Problems of misclassification are discussed in terms of the nature and frequency of variants. With the judicious choice of enzymes used to screen new stocks, these problems can be circumvented. Species relationships are updated using 11 enzymes. A dendrogram constructed from the matrix of genetic distances shows four clusters of species: (i) P. biaurelia, P. triaurelia; (ii) P. primaurelia, P. pentaurelia, P. sexaurelia, P. novaurelia; (iii) P. septaurelia, P. undecaurelia, P. tredecaurelia, P. quadecaurelia; and (iv) P. tetraurelia, P. octaurelia, P. decaurelia, P. dodecaurelia. Distances between the species are large, on the order of the differences between Drosophila species. The species are characterized by an extraordinary lack of geographical differentiation and great morphological similarity, which contrasts strongly with the molecular differentiation.     

Zooplankton in the ponds with tropical plants in the greenhouses of the Botanical Garden of the Jagiellonian University in Kraków

The presence of P. tetraurelia was found in the pond in "The Palm-House" greenhouse.     

G-protein modulators alter the swimming behavior and calcium influx of Paramecium tetraurelia

To assess the potential role of G-proteins in chemokinesis, Paramecium tetraurelia was pre-incubated with the G-protein modulator pertussis toxin. Pertussis toxin pretreatment significantly reduced Paramecium chemoattraction to sodium acetate and ammonium chloride in T-maze behavioral assays and depressed the frequency of avoidance reactions, indicating that heterotrimeric G-proteins may be involved with the motility response. To determine whether G-proteins exert their effect via the ciliary voltage-sensitive calcium channel, we examined responses of P. tetraurelia to the potent voltage-sensitive calcium channel agonist, deltamethrin. Pertussis toxin preincubation significantly reduced the toxic effects of deltamethrin exposure as determined by survival under depolarizing conditions and reduced the duration of backward swimming episodes in behavioral bioassays. Furthermore, non-hydrolyzable analogs of guanine nucleotides altered deltamethrin-stimulated calcium influx via calcium channels in isolated ciliary vesicles. Heterotrimeric G-protein subunits were subsequently detected in ciliary vesicles of P. tetraurelia by antibodies produced against Galpha and Gbeta subunits, and by 32P-ADP-ribosylation, indicating that proteins of the appropriate molecular weight are the target of pertussis toxin in these vesicles. These findings provide additional evidence that heterotrimeric G-proteins are associated with ciliary vesicles and that they play a role in the modulation of swimming behavior and the toxic action of deltamethrin in Paramecium.