Cytoplasmic microtubule organizing centers isolated from Polytomella agilis.

Basal body rootlets in Polytomella function as organizing centers for cytoplasmic microtbules in vivo. A method is described to isolate intact basal body-rootlet complexes. The integrity of the isolated complexes is confirmed by electron microscopy, and the rootlets are shown to be competent as initiation sites for the in vitro polymerization of brain microtubule protein.