Comparison of sequence differences in a variable 23S rRNA domain among sets of cryptic species of ciliated protozoa.

Studies were undertaken to discover the relative molecular distances separating some familiar forms of ciliated protozoa, and the genetic species they include. Sequences of 190 bases of the D2 domain of the large ribosomal nucleic acid molecule were obtained by polymerase chain reaction from protists of three distinctive groups of ciliated protozoa-Colpoda, Paramecium and Tetrahymena. Evolutionary trees were constructed for each set of sequences using the PHYLOGEN 1.

Ribosomal RNA sequencing of members of the Crypthecodinium cohnii (Dinophyceae) species complex; comparison with soluble enzyme studies.

Sixty-five members of the Crypthecodinium cohnii species complex were analyzed for sequence differences within the D2 region of the 23S ribosomal RNA molecule. On the basis of 46 sequence differences the strains fell into 19 distinct ribosets (strains of identical sequence), some with many members. Members of four of the seven major sibling species (widespread breeding groups) were each found within single ribosets.

Crypthecodinium and Tetrahymena: an exercise in comparative evolution.

Nucleotide sequences have been determined for the highly variable D2 region of the large rRNA molecule for over 60 strains of dinoflagellates. These strains were selected from a worldwide collection that represents all the known sibling species (compatibility groups, Mendelian species) in the sibling swarm referred to as Crypthecodinium cohnii. A phylogenetic tree has been constructed from an analysis of the variations in a length of about 180 bases, using PHYLOGEN string analysis programs.

Eukaryotic origins: string analysis of 5S ribosomal RNA sequences from some relevant organisms.

Using the PHYLOGEN tree-forming programs, we evaluate the published 5S rRNA sequences in certain of the files in the Berlin DataBank in an attempt to identify the connection between archaebacteria and the eukaryotic protists. These programs are based on methods of string analysis developed by Sankoff and others. Their discriminatory power is derived from their continuous realignment of sequences through repeated assessment of insertions and deletions as well as substitutions.

Shifting ditypic site analysis: heuristics for expanding the phylogenetic range of nucleotide sequences in Sankoff analyses.

We describe and illustrate a simple heuristic approach to the Sankoff methods for construction of parsimonious evolutionary trees from nucleotide sequence data. The procedure is intended to permit more valid inferences, particularly from relatively short sequences, concerning relationships among taxa separated for long time intervals. The procedure is based on the great variability of evolutionary plasticity among sites in the molecules and removes from consideration the more highly variable sites.

Ciliate evolution: the ribosomal phylogenies of the tetrahymenine ciliates.

We have assembled and analyzed nucleotide sequences for several different rRNA components from tetrahymenine ciliates. These include previously published and some new 5S and 5.8S rRNAs for a total of 18 species.

Comparison of ribosomal and isozymic phylogenies of tetrahymenine ciliates.

A recent analysis of sequence variations in ribosomal RNA's from 31 species of tetrahymenine ciliates groups them into 9 sets referred to as "ribosets." These species associations are not well correlated with the distributions of distinctive morphological characteristics. The phylogenetic structure suggests that modern "pyriform" tetrahymenines may be paraphyletic survivors of primitive design and that the morphologically distinctive forms may include examples of convergent evolution of derived forms.

New wild Tetrahymena from Southeast Asia, China, and North America, including T. malaccensis, T. asiatica, T. nanneyi, T. caudata, and T. silvana n. spp.

Tetrahymena of the T. pyriformis complex collected from varied habitats in Malaysia, Thailand, and The People's Republic of China include strains of the micronucleate species T. americanis and T.

The regulation of amounts and proportions of genetic elements in the macronuclei of Tetrahymena thermophila strains of diverse karyotype.

Measurements of the micronuclear DNA content of clones with assumed different degrees of micronuclear ploidy confirmed the triploid nature of one clone. The micronuclear DNA content of a presumptive haploid clone was found to be slightly higher than expected, whereas one of two aneuploid clones had an unexpectedly low micronuclear DNA content. The macronuclear DNA content of cells with macronuclei which had developed from triploid, diploid and probably haploid and aneuploid macronuclear-Anlagen is very similar.

Cytogenetics of triplet conjugation in Tetrahymena: origin of haploid and triploid clones.

Triplet conjugation occurs frequently when three different mating types of T. thermophila are mixed under appropriate conditions. Genetic studies show that fertilization is usually tripolar, with each conjugant contributing a pronucleus to one mate and receiving a pronucleus from the other.