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Abstract
SUMMARY: After extensive ethidium bromide (EB) treatment or ultraviolet irradiation or petite mutants could be isolated from the obligate aerobe Hansenula wingei. Petite-negativity is correlated with a lack of glucose repression. Hansenula wingei issensitive to EB on fermentable as well as non-fermentable carbon sources. Growth arrest by EB of single cells on agar is immediate but one or two divisions occur in liquid before the sensitive cells stop growing. Although EB treatment of the sensitive wild-type does not result in either petite mutagenesis or cell killing, there is a reversible inhibition of growth observed when EB-treated cells are plated on non-crmentable substrates. Mutants resistant to EB were isolated on either glucose + EB or glycerol + EB plates. Mutants resistant to EB in glycerol medium are also (csistant to EB in glucose medium. However, mutants isolated on glucose + EB medium are still sensitive to EB in glycerol medium. When mutants resistant to EB in glycerol medium revert to sensitivity they retain resistance to EB in glucose medium. Resistance to EB in glucose medium is recessive in the diploid.
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