Journal of General Microbiology (1976), 94,204-210 Printed in Great Britain The Isolation of Nuclei from the Filamentous Fungus

A method has been developed for isolating nuclei from the filamentous fungus Aspergillus nidulans. In this procedure, the mycelia from 14 to 16 h spore-derived cultures of A. nidulans M I, a stable diploid strain, were frozen with liquid nitrogen and homogenized in a Waring blender. After homogenization, the mycelia were warmed to 4 "C and the nuclei were purified from the homogenate by differential centrifugation followed by sedimentation through 2 ' I M-sucrose. The final nuclear yield was 15 to 20?<, based on DNA estimations. The purified nuclear pellet was free of whole cells. The morphology of the isolated nuclei resembled that of the in situ nuclei; they contained a nucleolus, chromatin, and had a surrounding double membrane. The purified nuclei were characterized by a DNA:RNA: protein ratio of I: 2.8: 8.7