Abstract
SUMMARY Two electrophoretically distinct classes of virus particles, designated fast (AfV-F) and slow (AfV-S) according to their relative electrophoretic mobilities, were isolated from the mycelium of Aspergillus foetidus, strain imi 41871. They were almost completely separated by dialysis against 0.03m-phosphate buffer, pH 7.6, in which F particles remained in suspension, while S particles precipitated, and were further purified by caesium chloride density gradient centrifugation. Electron microscopy showed that both classes were composed of isometric particles of similar diameter. RNA, prepared from both AfV-F and AfV-S, was double-stranded. In polyacrylamide gel electrophoresis AfV-F RNA was resolved into four main components with molecular weights of 2.31, 1.87, 1.70 and 1.44 × 106, while AfV-S RNA gave two components with molecular weights of 2.76 and 2.24 × 106. Both AfV-F and AfV-S could be separated by centrifugation in caesium chloride gradients into a number of fractions containing particles with different buoyant densities. Electrophoretic analysis of the RNA prepared from the virus fractions indicated that the multiple RNA components are not fragments released from a single virus particle, but are separately encapsidated in different particles.
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