Purification and characterization of plasmid-like DNA from the antimycotic producing fungus, Scytalidium flavo-brunneum.

The azasterol producing strain of Scytalidium flavo-brunneum (ATCC 28804) was examined for the presence of a plasmid-like DNA. Several different plasmid preparation procedures yielded DNA which migrated as single bands of equivalent molecular weight when analyzed by gel electrophoresis. Electron microscopy and lambda exonuclease digestion data were consistent with a covalently closed circular structure. A complete restriction map for a circular 9.1-kb plasmid-like DNA was deduced from analysis of restriction enzyme digests and Southern blot hybridizations of restriction fragments. Visualization of the plasmid by electron microscopy revealed a measured contour length of 8.9 kb, using pBR322 as a standard. Southern hybridization analysis using plasmid-like DNA as the probe detected no homology to the non-azasterol producing strains of Scytalidium flavo-brunneum or mitochondrial DNA from azasterol producing strain.