Search

Paramecium bursaria (Ehrenberg 1831) is a ciliate species living in a symbiotic relationship with green algae. The aim of the study was to identify green algal symbionts of P. bursaria originating from distant geographical locations and to answer the question of whether the occurrence of endosymbiont taxa was correlated with a specific ciliate syngen (sexually separated sibling group). In a comparative analysis, we investigated 43 P. bursaria symbiont strains based on molecular features. Three DNA fragments were sequenced: two from the nuclear genomes-a fragment of the ITS1-5.8S rDNA-ITS2 region and a fragment of the gene encoding large subunit ribosomal RNA (28S rDNA), as well as a fragment of the plastid genome comprising the 3' rpl36 -5' infA genes. The analysis of two ribosomal sequences showed the presence of 29 haplotypes (haplotype diversity Hd = 0.98736 for ITS1-5.8S rDNA-ITS2 and Hd = 0.908 for 28S rDNA) in the former two regions, and 36 haplotypes in the 3' rpl36 -5' infA gene fragment (Hd = 0.984). The following symbiotic strains were identified: Chlorella vulgaris , Chlorella variabilis , Chlorella sorokiniana and Micractinium conductrix . We rejected the hypotheses concerning (i) the correlation between P. bursaria syngen and symbiotic species, and (ii) the relationship between symbiotic species and geographic distribution.

Although some Paramecium species are suitable research objects in many areas of life sciences, the biodiversity structure of other species is almost unknown. In the current survey, we present a molecular analysis of 60 Cypriostomum strains, which for the first time allows for the study of intra- and interspecific relationships within that subgenus, as well as the assessment of the biogeography patterns of its morphospecies. Analysis of COI mtDNA variation revealed three main clades (separated from each other by approximately 130 nucleotide substitutions), each one with internal sub-clusters (differing by 30 to 70 substitutions - a similar range found between P. aurelia cryptic species and P. bursaria syngens). The first clade is represented exclusively by P. polycaryum; the second one includes only four strains identified as P. calkinsi. The third cluster seems to be paraphyletic, as it includes P. nephridiatum, P. woodruffi, and Eucandidatus P. hungarianum. Some strains, previously identified as P. calkinsi, had COI sequences identical or very similar to P. nephridiatum ones. Morphological reinvestigation of several such strains revealed common morphological features with P. nephridiatum. The paper contains new information concerning speciation within particular species, i.e. existence of cryptic species within P. polycaryum (three) and in P. nephridiatum (six)., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Paramecium bursaria (Ehrenberg 1831), a freshwater ciliate, typically harbors hundreds of green algal symbionts inside the cell. The aim of present study was the molecular identification of newly analyzed P. bursaria symbionts. The second aspect of the present survey was testing a hypothesis whether endosymbionts prefer the specified syngen of the host, and the specified geographical distribution. Ten strains of endosymbionts isolated from strains of P. bursaria originating from different geographical locations were studied. We analyzed for the first time, both the fragment of plastid genome containing 3'rpl36-5' infA genes and a fragment of a nuclear gene encoding large subunit ribosomal RNA (LSU rDNA). The analysis of the LSU rDNA sequences showed the existence of 3 haplotypes and the haplotype diversity of 0.733, and 8 haplotypes for the 3'rpl36-5' infA gene fragment and haplotype diversity of 0.956. The endosymbionts isolated from P. bursaria strains were identified as Chlorella vulgaris, Ch. variabilis and Micractinium conductrix. There was no correlation between the syngen of P. bursaria and the species of endosymbiont.

The demarcation of boundaries between protist species is often problematic because of the absence of a uniform species definition, the abundance of cryptic diversity, and the occurrence of convergent morphology. The ciliates belonging to the Paramecium aurelia complex, consisting of 15 species, are a good model for such systematic and evolutionary studies. One member of the complex is P. sonneborni, previously known only from one stand in Texas (USA), but recently found in two new sampling sites in Cyprus (creeks running to Salt Lake and Oroklini Lake near Larnaca). The studied Paramecium sonneborni strains (from the USA and Cyprus) reveal low viability in the F1 and F2 generations of interstrain hybrids and may be an example of ongoing allopatric speciation. Despite its molecular distinctiveness, we postulate that P. sonneborni should remain in the P. aurelia complex, making it a paraphyletic taxon. Morphological studies have revealed that some features of the nuclear apparatus of P. sonneborni correspond to the P. aurelia spp. complex, while others are similar to P. jenningsi and P. schewiakoffi. The observed discordance indicates rapid splitting of the P. aurelia-P. jenningsi-P. schewiakoffi group, in which genetic, morphological, and molecular boundaries between species are not congruent., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

Paramecium is one of the most studied genera among ciliates. In particular, it is a model organism for investigation of the sibling species problem (also known as the cryptic species problem), spatial distribution, and its role in speciation. The global distribution of Paramecium species and of sibling species belonging to the P. aurelia species complex (Ciliophora, Protista) still need study, e.g. sampling in some territories has been quite limited, while Europe has been investigated for years with the majority of the P. aurelia species isolated from here. The large territory of Yakutia (republic Sakha in the Russian Federation), known for its climate extremes and continuous permafrost that extended over several glacial and interglacial cycles of the Pleistocene, has not been studied before. In the present study we collected paramecia in the central part of Yakutia. Newly established strains were identified to species according to morphology and, in case of the P. aurelia complex, by crossing with the test strains (the reference strains for the particular species). New stands of P. primaurelia, P. biaurelia and P. novaurelia were described from the territory of Yakutia.

Paramecium bursaria is composed of five syngens that are morphologically indistinguishable but sexually isolated. The aim of the present study was to confirm by molecular methods (analyses of mitochondrial COI) the identification of P. bursaria syngens originating from different geographical locations. Phylograms constructed using both the neighbor-joining and maximum-likelihood methods based on a comparison of 34 sequences of P. bursaria strains and P. multimicronucleatum, P. caudatum and P.calkinsi strains used as outgroups revealed five clusters which correspond to results obtained previously by mating reaction. Our analysis shows the existence of 24 haplotypes for the COI gene sequence in the studied strains. The interspecies haplotype diversity was Hd = 0.967. We confirmed genetic differentiation between strains of P. bursaria and the occurrence of a correlation between geographical distribution and the correspondent syngen.

P. aurelia is currently defined as a complex of 15 sibling species including 14 species designated by Sonneborn (1975) and one, P. sonneborni, by Aufderheide et al. (1983). The latter was known from only one stand (Texas, USA). The main reason for the present study was a new stand of Paramecium in Cyprus, with strains recognized as P. sonneborni based on the results of strain crosses, cytological slides, and molecular analyses of three loci (ITS1-5.8S-ITS2-5'LSU rDNA, COI, CytB). The new stand of P. sonneborni in Europe shows that the species, previously considered endemic, may have a wider range. This demonstrates the impact of under-sampling on the knowledge of the biogeography of microbial eukaryotes. Phylogenetic trees based on all the studied fragments revealed that P. sonneborni forms a separate cluster that is closer to P. jenningsi and P. schewiakoffi than to the other members of the P. aurelia complex., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Paramecium putrinum (Claparede & Lachmann 1858) is one of the smallest (80-140 μm long) species of the genus Paramecium. Although it commonly occurs in freshwater reservoirs, no molecular studies of P. putrinum have been conducted to date. Herein we present an assessment of molecular variation in 27 strains collected from widely separated populations by using two selected DNA fragments (ITS1-5.8S-ITS2-5'LSU rDNA and COI mtDNA). Both the trees and haplotype networks reconstructed for both genome fragments show that the studied strains of P. putrinum form five main haplogroups. The mean distance between the studied strains is p-distance=0.007/0.068 (rDNA/COI) and exhibits similar variability as that between P. bursaria syngens. Based on these data, one could hypothesize that the clusters revealed in the present study may correspond to previously reported syngens and that there are at least five cryptic species within P. putrinum., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The occurrence of species of the P. aurelia complex has been studied at a large scale in Europe and the majority of known species of the complex have been found there. However, a different number of habitats were studied in particular zones of Europe, the greatest number in the central zone. Herein new stands of several species of the Paramecium aurelia complex are presented from Europe including P. primaurelia, P. biaurelia, P. triaurelia, P. octaurelia, P. novaurelia, and P. dodecaurelia. In South America, studies concerning the distribution of the P. aurelia species complex were carried out only occasionally and the presence of some cosmopolitan species of the complex has been recorded, i.e. P. primaurelia, P. biaurelia, and P. tetraurelia. Recently, new stands of P. primaurelia and P. septaurelia were found in Ecuador. Ciliate biogeography and distribution is also discussed.

The relevance of geographical distribution and the roles of dispersal and spatial isolation during the speciation of microorganisms are nowadays of great interest. The Paramecium aurelia species complex is a perfect model system to explore these questions given its long history as a study subject and broad distribution. However, the world-wide distribution of the Paramecium aurelia complex (Ciliophora, Protista) still needs study, e.g., sampling in the southern hemisphere has been quite limited, while Europe has been investigated for years, with the majority of aurelia species isolated from here. Recently, new stands of species of the P. aurelia complex were found in southern Europe (Malta, Bulgaria, Cyprus) and in the Czech Republic (P. primaurelia, P. triaurelia, P. octaurelia). In Africa (Republic of South Africa), new stands of P. primaurelia, P. triaurelia, and P. octaurelia were found. Interestingly, the rare species P. triaurelia, and P. octaurelia were found to co-occur both in South Africa (SA 13) and the Czech Republic (CKV 8). Newly established strains were identified to species by crossing with the test strains (the reference strains for the particular species).

New stands of P. primaurelia, P. biaurelia, and P. dodecaurelia were found in Russia. P. primaurelia was recorded in Tulun (Siberia, Irkutsk region) and in three stands situated on the Kamchatka peninsula: in Lake Chalaktyrskoye, in the Valley of Geysers, and Petropavlovsk Kamchatski. P. biaurelia was also found in Tulun and in two stands in the vicinity of Lake Baikal and the Buriatia region. P. dodecaurelia was recorded in Cheboksary in European Russia and in other stands situated in Asian Russia: Novosibirsk, the vicinity of Lake Baikal, Buriatia, Kamchatka (Petropavlovsk Kamchatski, Lake Chalaktyrskoye, and Nalychevo). These data extend the ranges of species of the P. aurelia complex in Russia, however, this large territory remains understudied.

This is the first attempt to resolve the phylogenetic relationship between different syngens of Paramecium bursaria and to investigate at a molecular level the intraspecific differentiation of strains originating from very distant geographical locations. Herein we introduce a new collection of five P. bursaria syngens maintained at St Petersburg State University, as the international collection of syngens was lost in the 1960s. To analyze the degree of speciation within Paramecium bursaria, we examined 26 strains belonging to five different syngens from distant and geographically isolated localities using rDNA (ITS1-5.8S-ITS2-5'LSU) fragments, mitochondrial cytochrome c oxidase subunit I (COI), and H4 gene fragments. It was shown that P. bursaria strains of the same syngens cluster together in all three inferred molecular phylogenies. The genetic diversity among the studied P. bursaria strains based on rDNA sequences was rather low. The COI divergence of Paramecium bursaria was also definitely lower than that observed in the Paramecium aurelia complex. The nucleotide sequences of the H4 gene analyzed in the present study indicate the extent of genetic differences between the syngens of Paramecium bursaria. Our study demonstrates the diagnostic value of molecular markers, which are important tools in the identification of Paramecium bursaria syngens., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

This is the first phylogenetic study of the intraspecific variability within Paramecium multimicronucleatum with the application of two-loci analysis (ITS1-5.8S-ITS2-5'LSU rDNA and COI mtDNA) carried out on numerous strains originated from different continents. The species has been shown to have a complex structure of several sibling species within taxonomic species. Our analysis revealed the existence of 10 haplotypes for the rDNA fragment and 15 haplotypes for the COI fragment in the studied material. The mean distance for all of the studied P. multimicronucleatum sequence pairs was p=0.025/0.082 (rDNA/COI). Despite the greater variation of the COI fragment, the COI-derived tree topology is similar to the tree topology constructed on the basis of the rDNA fragment. P. multimicronucleatum strains are divided into three main clades. The tree based on COI fragment analysis presents a greater resolution of the studied P. multimicronucleatum strains. Our results indicate that the strains of P. multimicronucleatum that appear in different clades on the trees could belong to different syngens., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Paramecium calkinsi (Ciliophora, Protozoa) is a euryhaline species which was first identified in freshwater habitats, but subsequently several strains were also collected from brackish water. It is characterized by clockwise spiral swimming movement and the general morphology of the "bursaria type." The present paper is the first molecular characterization of P. calkinsi strains recently collected in distant regions in Russia using ITS1-5.8S- ITS2-5'LSU rDNA (1100bp) and COI (620bp) mtDNA sequenced gene fragments. For comparison, our molecular analysis includes P. bursaria, exhibiting a similar "bursaria morphotype" as well as species representing the "aurelia type," i.e., P. caudatum, P. multimicronucleatum, P. jenningsi, and P. schewiakoffi, and some species of the P. aurelia species complex (P. primaurelia, P. tetraurelia, P. sexaurelia, and P. tredecaurelia). We also use data from GenBank concerning other species in the genus Paramecium and Tetrahymena (which used as an outgroup). The division of the genus Paramecium into four subgenera (proposed by Fokin et al. 2004) is clearly presented by the trees. There is a clear separation between P. calkinsi strains collected from different regions (races). Consequently, given the molecular distances between them, it seems that these races may represent different syngens within the species., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

New stands of species of the Paramecium aurelia complex are presented in the paper, P. primaurelia recorded in Italy (Pisa) and in Morocco (Marrakesh), P. biaurelia in Italy (Calabria), P. triaurelia in Morocco (Ifrane), P. pentaurelia in Greece (Kastorya), and P. dodecaurelia in Italy (Padua).

The review summarizes modern views on to the structure and differentiation of the nuclear apparatus in ciliates. The genetic system of ciliates (type Ciliophora) includes two types of nuclei: germinal micronucleus (MIC) and somatic macronucleus (MAC). The MAC development is associated with the rearrangement of the MIC genome, which includes chromosome fragmentation and chromatin diminution. The loss of DNA constitutes from 10-15% (Tetrahymena termophila) to 95-98% of the genome in spirotrichs (Stylonychia, Oxytricha, and Euplotes). Analysis of molecular mechanisms underlying nuclear dualism in ciliates promoted radical revision of the concept on the interactions and roles of MAC and MIC. The micronucleus, as an inactive element, is an ideal field for the invasion and further expansion of mobile genetic elements. Chromatin diminution plays the purifying role, restoring the native genome structure. The process of recognition of "genetic garbage" to be eliminated has many features in common with the siRNA-mediated heterochromatization. The presence of this mechanism in very early radiated eukaryotic lineages (Opistokonta and Chromalveolata), indicates that it arose at the earliest stages of the eukaryotic evolution, probably, as a mechanism promoting genome integrity and stability.

New stands of Paramecium biaurelia, P. triaurelia, P. tetraurelia, P. pentaurelia, P. novaurelia, and P. dodecaurelia were recorded in Russia. Especially interesting is the record of P. novaurelia in Vladivostok, Russian Far East, as it is a very rare species outside of Europe. The distribution of species of the Paramecium aurelia complex in Eurasia with emphasis on findings in Russia is discussed.

The ciliates Paramecium bursaria contain endosymbiotic green algae Chlorella spp. in their cytoplasm. The algae isolated from P. bursaria are sensitive to large DNA-containing viruses of the family Phycodnaviridae. The type virus of this family is PBCV-1 (Paramecium bursaria Chlorella virus). Investigation of the total DNA of P. bursaria clones by pulse-field electrophoresis (PEP) revealed a pronounced band on PEP profiles of some P. bursaria clones; the band was formed by DNA molecules of approx. 300 kb. This band probably contained the DNA of chlorella virus. Two approaches were used in the present work to confirm this hypothesis. Microbiological tests were used to scan a collection of P. bursaria clones for specific types of viruses; the 300-kb band was revealed only in the PEP profiles of virus-containing clones. Blot hybridization of P. bursaria total DNA separated by pulse-field electrophoresis with the virus-specific probe revealed that the band under study contained the DNA of a chlorella virus. Paramecium clones were shown to contain approx. 10(5) copies of nonintegrated viral DNA.

New stands of Paramecium dodecaurelia were found in Russia, Ukraine, Kazahstan, Poland, and Tenerife. Molecular studies (RAPD and sequencing of LSU rRNA and CO1 mtDNA gene fragments) of P. dodecaurelia strains depicted intraspecific polymorphism within the species, revealed as distinct differences between strains from the USA in comparison with strains from different regions of the Palearctic.

The macronuclear genomes of two sibling species belonging to the Paramecium aurelia complex--P. primaurelia and P. novaurelia--were analyzed by pulsed-field gel electrophoresis (PFGE). Their electrophoretic karyotypes showed a continuous spectrum of different-sized DNA molecules with a species-specific pattern of banding, which was reproducible and did not change with strain senescence. Thus, P. aurelia macronuclear PFGE profiles could be described by an approach analogous to that used for the description of metaphase chromosome banding patterns. At first, well-identifiable regions (size fractions) of a PFGE profile, which can be seen at any resolution, are determined. Then, the bands of the second order of resolution (subfractions) can be defined in some of these regions. The blocks of the first and second orders can be utilized as inner markers of the PFGE profile allowing precise comparison of different PFGE profiles. Such comparative analysis has demonstrated some marking differences in organization of the macronuclear genomes of P. primaurelia and P. novaurelia, and low level of intraspecific polymorphism. Worth noting is that the P. novaurelia strain isolated in USA was different from all other analyzed P. novaurelia strains originating from Europe. The nature of banding of P. aurelia PFGE profiles is discussed. The revealed high order and stability of the macronuclear genome organization makes possible searching for new approaches to study the mechanisms of this non-trivial genome formation and maintenance. Further PFGE analysis of the macronuclear genomes of the other Paramecium species in relation with the Paramecium phylogeny may provide insights into the directions of the evolution of the macronuclear genome in Ciliata.

The Volga, which is the largest river in Europe (3690 km long), flows from the north (Tver' region) to the south (Caspian Sea), and its extensive basin (1380 km2) includes very different biotopes. Thus, analysis ofthe occurrence of Paramecium species along this large river basin may significantly enhance our understanding of species distribution according to temperature regime, food richness and other possible factors. The present paper concerns the occurrence of species of the P. aurelia complex in the sampling areas of the Upper Volga River, and a comparison with the occurrence of species of the P. aurelia complex in the Lower Volga region. In the Upper Volga basin, P. biaurelia was the most abundant among species of the complex recorded (among P. triaurelia, P. decaurelia, P. dodecaurelia), in the Lower Volga region eight species of the complex were recorded (P. primaurelia, P. biaurelia, P. triaurelia, P. pentaurelia, P. sexaurelia, P. septaurelia, P. novaurelia, P. decaurelia).

The presence of Paramecium sexaurelia from the Paramecium aurelia complex was recorded for the first time in China (Beijing). RAPD fingerprints (band patterns) of P. sexaurelia strains, the new strain from China and others from Asia, as well as from Europe and Puerto Rico, showed polymorphism within the species as several groups of genotypes characterized by different band patterns.

The presence of Paramecium decaurelia from the Paramecium aurelia species complex was demonstrated in Yaroslavl, Russia, (European part, northwestern Russia) and in the Altai Mts (Asiatic part of Russia, western Siberia). RAPD-PCR fingerprints of the newly identified strains of P. decaurelia, rare throughout the world, were compared to those characteristic for the other known strains ofthe species. P. decaurelia strains show some polymorphism within species, strains from Russia have 60% similarity of band patterns, and strains from USA and Japan about 70% similarity of band patterns.

Paramecium strains collected in Central Russia, Western Siberia (the West Siberian Lowland and the Altai Mountains in the south) were studied. The presence of P. caudatum, P. bursaria, P. multimicronucleatum, P. polycaryum, and four species of the P. aurelia complex, i.e. P. primaurelia (in Omsk), P. biaurelia (in Krasnoyarsk and the Altai Mountains), P. triaurelia (in Krasnoyarsk), and P. pentaurelia (in Novosibirsk, Altai Foreland, and Altai Mountains) was revealed. P. triaurelia and P. pentaurelia were found for the first time in Asia.

The presence of P. primaurelia, P. biaurelia, P. triaurelia, and P. novaurelia of the P. aurelia complex was revealed in the studied region of Russia. RAPD-PCR fingerprints (band patterns) of newly identified P. novaurelia strains from Russia were compared to those characteristic for the other chosen European strains of the species. The strains revealed intraspecific polymorphism as several groups of genotypes confirming the existence of polymorphism within P. novaurelia.

New stands of rare species of the Paramecium aurelia complex were found in Europe, i.e. P. pentaurelia and P. dodecaurelia in Italy and P. septaurelia in Germany. The species were identified by mating reactions with the standard strains of each species. Their relationships with some other known strains of particular species were studied by classical strain crosses (survival in F1 and F2 generations) and by comparison of RAPD-PCR fingerprints. The presence of the cosmopolitan species P. tetraurelia in Italy was also recorded.

The presence of several species of the P. aurelia complex was revealed in the studied regions. In the Volgograd region P. primaurelia, P. biaurelia, P. triaurelia, and P. novaurelia were recorded. In the Astrakhan Nature Reserve P. primaurelia, P. pentaurelia, P. sexaurelia, and P. septaurelia were identified. Among these species, P. septaurelia was recorded for the first time in Europe, known before only from the territory of the USA, P. pentaurelia and P. sexaurelia are species rare in Europe. The studied regions are very rich in species of the P. aurelia complex and worthy of future studies.

The karyotype of the chicken Gallus gallus domesticus was studied by means of pulsed-field electrophoresis. An electrokaryogram was obtained for the microchromosomal (MI) portion of the chicken genome. Chicken MIs were separated into two fractions. A fraction with a higher mobility included MIs sized 3.4-4.8 Mb; the lower size limit of a less mobile fraction corresponded to MIs of approximately 5 Mb. The smallest MI in the chicken karyotype was estimated at 3.4 +/- 0.25 Mb.

Particles of a newly described endosymbiont of Paramecium caudatum, clone M-115, here referred to as iota--particles, are Gram--negative bacteria. The symbionts are only present within macronuclei and not in the cytoplasm or in the micronuclei. The cells of clone M-115 iota do not display any killer-effect when mixed with "clean" cultures of Paramecia. In life cycle of the symbiont, there is an alternation of two morphological forms: a spindle-shaped form 2.0--2.5 microns long and a rod-shaped form -- about 18 microns long. The data obtained revealed a high ability to infect cell of "clean" clones of P. caudatum with iota-particles. The antagonistic relationships between two different species of endonucleosymbionts: iota- and omega-particles, are detected. The revealed biological features of iota can be used for studying the mechanisms of nuclear differentiation in ciliates.