Microfilaments and cytoplasmic microtubules in cell division cycle mutants of Schizosaccharomyces pombe.

The occurrence of axial cytoplasmic microtubules (25 nm in diameter) and of microfilaments (7 nm in diameter) associated in bundles just below the plasma membrane of the yeast Schizosaccharomyces pombe is described. Both types of cytoplasmic filamentous structures were present in the cell division cycle mutant cdc 12-112 of this fungus incubated for 6 h at the restrictive temperature of 35 degrees C. Microtubules and microfilaments probably function in septum formation and (or) in the volume-related control of the terminal phenotype of the mutant.