DNA from isolated pellicles of Tetrahymena.

Large pellicle fragments were isolated from Tetrahymena pyriformis, strain T, by 2 procedures : homogenization after treatment with 40 % ethanol at — 20 °C, or direct homogenization in a sucrose-EDTA buffer. All preparations contained entrapped mitochondria. DNA prepared from these pellicles was analysed on a CsCl gradient, and contained 3 components of buoyant densities 1-685, 1-688, and 1698 g cm"" in variable proportions. The component at 1-685 g cm" is similar in density to mitochondrial DNA and those at 1-688 and 1-698 g cm" to components of nuclear DNA. Most pellicle preparations contained a higher proportion of the heavy component (1-698 g cm") than does nuclear DNA. A similar enrichment of this component could be demonstrated in high-speed pellets from fragmented nuclei. No unique pellicle-associated component could be demonstrated. No DNA could be isolated from very pure preparations of oral plates and we conclude that there is no evidence for the presence of a specific DNA associated with the pellicle.