The Kinetic and Analytical Complexities of the DNA Genomes of Certain Marine and Fresh‐Water Ciliates1

Abstract

We investigated the macronuclear DNA genomes of several marine and fresh‐water ciliates. The marine forms studied were: Uronema nigricans, Parauronema virginianum, Parauronema acutum, and two strains of Miamiensis avidus; the fresh‐water ciliates included: Tetrahymena pyriformis, Paramecium octaurelia, and P. caudatum. The organisms were cultured axenically and the DNA extracted from isolated and purified macronuclear preparations. Reassociation rate constants of purified DNA preparations used to calculate kinetic complexity were determined both optically and by hydroxyapatite chromatography. Analytical complexity was determined chemically. Ciliate macronuclear DNA appeared to reassociate as a single unique sequence, except for a small fraction (4% of the total DNA) that was repetitive and renatured rapidly. Values for the kinetic complexities of macronuclear DNA in these forms varied over a relatively narrow range, from 1.5 to 3.8 times 1010 daltons, and were only 7–15x larger than that of the bacterium Escherichia coli. On the other hand, values for analytical complexities of macronuclear DNA of marine and fresh‐water ciliates varied over two orders of magnitude and were related to the size of the animals. It is suggested that ploidy levels of macronuclear DNA in these ciliates may represent a functionally permanent amplification of the genome.

Interstitial telomeres are hotspots for illegitimate recombination with DNA molecules injected into the macronucleus of Paramecium primaurelia.

“…Otherwise, insertion was located in AT-rich sequences, which is not unexpected in an organism with a AT content of -75 % (MacTavish and Sommerville, 1980;Soldo et al, 1981). We show here that the number of interstitial telomeres per macronuclear genome equivalent is -40, and because we estimate the number of chromosomes to be of a few Lindreds there is roughly one interstitial telomere per 10 chromosomes.…”

“…No conserved or repetitive sequence elements other than the ones discussed below were observed. Paramecium macronuclear DNA is adenine-and thymine-rich (AT-rich; Gibson and Martin, 1971;MacTavish and Sommerville, 1980;Soldo et al, 1981) and all insertion sites were in AT-rich sequences, without any significant open reading frames. Likewise, no duplication of even short repeats could be detected at the 5' and 3' insertion boundaries for any clone; Insertion frequently occurs in or near internal telomeric repeats A striking feature revealed by the junction sequences was the presence of telomeric repeats next to two insertion junctions (Inl and In7; see Figure 3b).…”

“…When BS1 and more clearly BS2 DNA were cut with EcoRI (there is no EcoRI site in the BS fragment), the hybridization pattern appeared as a practically continuous smear extending from -1.5 kb to > 14 kb, demonstrating the multiplicity of sites into which insertion occurred (lane E, Figure 1). (Cummings, 1975;MacTavish and Sommerville, 1980;Soldo et al, 1981 extracted and cut with EcoRJ. The autoradiogram in Figure 2 shows that all the lambda phages contained an EcoRI fragment of a size > 1.7 kb hybridizing with the BS probe.…”

Phenotypic conversion of mating type specificity induced by transplantation of macronucleoplasm inParamecium caudatum

“…Because the macronucleus of P. caudatum is highly polyploid (Soldo et al 1981) as in other ciliates, dosage effects among genes may appear. P. caudatum is a convenient material for transformation experiments by injection of macronucleoplasm, because it has a large macronucleus and there have been no reports of phenotypic assortment and autogamy.…”

Neutral Lipids, their Fatty Acids, and the Sterols of the Marine Ciliated Protozoon, Parauronema acutum

“…While several of these marine ciliates, particularly Uronema , have been studied by electron microscopy (Kaneshiro and Holz 1976) and some physiological studies have been carried out on Miamiensis avidus and Uronema (Kaneshiro, Dunham, and Holz 1969; Thomson and Kaneshiro 1968), most studies have utilized P. acutum. These studies have focused on the nutrition, physiology, and xenosomes of P. acutum (Soldo 1978, 1987; Soldo et al 1986; Soldo, Brickson, and Larin 1981, 1983; Soldo, Godoy, and Larin 1978). Very little is known about the biochemistry of this ciliate.…”