Esterase Variants in Four Species of the Paramecium aurelia Complex1

One hundred eighty-eight stocks of Paramecium primaurelia, P. biaurelia, P. tetraurelia, and P. octaurelia were grown axenically and tested for five esterases, visualized by starch gel electrophoresis, in a search for variant stocks. The five esterases can be distinguished on the bases of their substrate specificity, sensitivity to an inhibitor, and response to different growth conditions. This paper addresses the nature of the electrophoretic change in mobility of the variant stocks in order that species relationships can be more accurately assessed. Crosses carried out in all four species show that single genes determine the differences in mobility between variant and common subtypes. Extracts of variant stocks that gave similar patterns were run against each other, tested for their sensitivity to the inhibitor, and the pattern was compared to that found in extracts of stocks with variant and common subtypes in other species. The majority of the variants in P. primaurelia, P. tetraurelia, and P. octaurelia show an electrophoretic mobility characteristic of a common subtype, or a variant, in another species. The same proportion of variant subtypes as common subtypes have mobilities similar to esterase subtypes found in other species. Of the four species examined in this paper, P. tetraurelia and P. octaurelia appear to be most closely related on the basis of shared esterase subtypes. In P. biaurelia the mobilities of most of the variants are unique, as are the common esterase subtypes in this species. P. biaurelia stands out as having the greatest number of esterase subtypes, with very few of them homologous to subtypes found in other species. This observation supports the idea of greater diversification of stocks within P. biaurelia than for the other three species.     

Paramecium tredecaurelia of the Paramecium aurelia complex in Israel

The paper concerns the finding of a new habitat (Kiryat Motzkin, north of Haifa, Israel) of Paramecium tredecaurelia from the P. aurelia complex. This is only the forth known locality of the species in the world. Previously, its strains were obtained from widely separated localities: the River Seine, Paris, France; Benenitra, Madagascar, and the Cuernavaca Valley, Taxco, Mexico. The studied strain originating from Israel was identified as P. tredecaurelia on the basis of the strong (90%) conjugation between the complementary mating type of the examined clones with the appropriate standard strain 209 of P. tredecaurelia from Paris, France (restricted to odd mating type). However, the strain from Israel is restricted to the even mating type.     

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.     

Paramecium sexaurelia of the Paramecium aurelia species complex in Thailand

The clones originating from Thailand, Phuket Island, were identified as Paramecium sexaurelia.     

Cytochrome b sequence data suggest rapid speciation within the Paramecium aurelia species complex

We investigated mitochondrial Cytochrome b sequences from all 15 members of the enigmatic Paramecium aurelia species complex (Ciliophora). The analysis revealed high genetic distances between the different P. aurelia species (6.1-19.8%) and a largely unresolved, star-like phylogenetic tree. This result strongly supports a rapid radiation in the evolutionary history of this species complex and it correlates well with the hypothesis that the extant species diversity may have originated from the neutral consequences of a whole genome duplication in the common ancestor of P. aurelia.     

Studies on the macronucleus of Paramecium aurelia

Following specific incorporation of tritiated thymidine into the DNA of the macronucleus of Paramecium aurelia for varying periods of time the vast majority of silver grains in electron microscope autoradiographs are associated with the area containing the small bodies and matrix. At best only 5% of the silver grains overlying the macronucleus are attributable to the large bodies. This is consistent with the view that the large bodies are the nucleoli of the macronucleus.     

Further Nutritional Requirements of Paramecium aurelia

SYNOPSIS. An acetone-insoluble yeast fraction required for axenic growth of P. aurelia , stock 51, variety 4, sensitive , after fractionation contained at least 3 essential components: (1) one soluble in perchloric acid and completely replaceable by a mixture of ribosides or ribotides; (2) one inactivated after digestion with trypsin, chymotrypsin or papain. Proteose-Peptone restored activity to this preparation, which suggests a peptide requirement; and (3) one not yet characterized.
As for the purine and pyrimidines, these combinations, in decreasing order of activity, supported growth: guanosine + cytidine, guanosine + uridine, guanylic acid + cytidylic acid, and guanylic acid + uridylic acid. Each combination was maximally effective when the molar purine: pyrimidine ratio was ∼ 0.4. On a molar basis, the minimal riboside combinations were ∼ 1.3 × more active than the ribotides.
Sparing of the purine and pyrimidine requirement was also investigated. In the presence of limiting amounts of guanylic acid, the following compounds, in decreasing order of activity, had sparing activity: deoxyguanosine, inosine, xanthosine, adenylic acid, and guanine. Adenine, adenosine, and deoxyadenosine were inhibitory under the test conditions. The requirement for cytidylic acid was spared by deoxycytidine, uridine, uridylic acid, deoxyuridine, thymidine, thymine, and uracil, in descending order.     

Species of the Paramecium aurelia complex in Italy

New stands of Paramecium pentaurelia were recorded in Valmarana, Veneto region in Italy and one stand of P. primaurelia was found at the same locality.     

Pyrimidine Dimers in the DNA of Paramecium aurelia

The production and fate of thymine-containing pyrimidine dimers in Paramecium aurelia DNA was investigated in three experimental series: production of dimers by UV irradiation, fate of dimers in the dark, and “loss of photoreactivability of dimers.” It is shown that cyclobutyl dimers are made by UV irradiation of Paramecium DNA in vivo, that because of cytoplasmic absorption the number of dimers made in DNA irradiated in vivo is much lower than in DNA irradiated in vitro, that dimers are lost from animals incubated in the dark after irradiation, and that all the dimers that remain in the animals can be destroyed by photoreactivating illumination. Since mutation induction is photoreactivable, these and previous photoreactivation data suggest that pyrimidine dimers are important in mutation induction in P. aurelia.     

Studies on the surface coat of Paramecium aurelia

Summary The plasma membrane of Paramecium aurelia is covered with a ruthenium red stainable surface coat. Results obtained after digestion with pronase, trypsin and neuraminidase suggest the glycoprotein nature of this structure. Lipid extraction also affects the surface coat forming material. The results are consistent with the model proposed by Ginsburg and Kobata dealing with spatial configuration of the surface coat components.Authors are grateful to Mrs. D. Kucharczyk for very efficient technical assistence, to Mrs. Z. Kaminska for sectioning the material and Mr. A. Renski for help with the electron microscope service.     

Anatomy of mitochondrial DNA from Paramecium aurelia

Summary The linear genome of mitochondrial DNA from four species of Paramecium aurelia was investigated with respect to restriction endonuclease fragments, location and number of ribosomal RNA genes, and interspecies EcoRI and HindIII fragment homologies. One copy of each of the rRNA genes was found in all four species and the 14s and 20s rRNA genes were separated by at least 3,000 bp. R-Loop analysis of the 20s rRNA gene did not reveal the presence of an intervening sequence. Interspecies homology studies showed species 1, 5, and 7 to have a high degree of homology but species 4 was less than 50% homologous to species 1 mt DNA. For all four species, rRNA genes showed good homology indicating that these DNA sequences are highly conserved, even between species having many non-homologous regions. A major region of DNA which displayed little homology between species 1 and 4 was that fragment containing sequences essential for initiation of DNA replication.     

Studies on the surface coat of Paramecium aurelia

Summary Correlations between the presence of surface coat and immobilization antigen of Paramecium tetraurelia were studied. Supravital, partial removal of the surface coat resulted in accelerated response of monobacterially and axenically grown cells to the homologous antiserum. Ciliates pretreated with trypsin or pronase (0.5mg/ml for 45 min at 0–4° C) were immobilized approximately twice as fast as untreated control cells. The probable localization of at least part, of the immobilization antigen within the surface coat of P. tetraurelia is discussed.The author thanks Prof. S. Dryl (Department of Cell Biology, M. Nencki Institute of Experimental Biology) and Prof. T.M. Sonneborn (Department of Zoology, Indiana University, Bloomington, USA) for donating antisera and for helpful discussion