Gene Control of Resistance Vs. Sensitivity to Actidione in Saccharomyces.

A modified Burkholder's medium (table 1) autoclaved a t 15 lbs. pressure for 15 minutes after being adjusted to pH 5 was used in 10 ml amounts in broth tubes, or 3 % agar was added for use in petri dishes. Actidione stock solution (10 mg of actidione in 100 ml of water) was sterilized by Seitz filtration, kept in a refrigerator until used, and added aseptically to the medium after autoclaving. One loopful of cells from a 24 hour culture was transferred to a 6 ml water blank to make a final turbidity of about 150 Klett units. One loopful of this suspension containing about 60,000 cells was used to inoculate a broth tube or planted on a spot about 1 cm in diameter on an agar plate. Tubes and plates were incubated a t 30°C. Results of growth in tubes were recorded after each 24-hour incubation (up to 96 hours) with a Klett Summerson Photoelectric colorimeter, using a 420 mp blue filter, with the zero point adjusted against an uninoculated broth tube. Growth on agar was recorded a t four different quantitative levels; 0, no growth; 1, discrete colonies; 2, irregularly confluent growth; and 3, fully confluent growth.