Cytochrome abnormalities and cyanide resistant respiration in extranuclear mutants of Aspergillus nidulans

Abstract

The cytochrome spectra of two extranuclear mutants of A. nidulans and the double mutant recombinant formed from them have been examined both at room temperature and at the temperature of liquid N2 and compared with those of the wild type strain. The oligomycin resistant, slow growing mutant contained an increased amount of cytochrome c without any loss of cytochromes b and a,a3. The cold sensitive mutant, apparently normal when grown at 37C, showed an increased amount of cytochrome c and a partial loss of cytochromes b and a,a3 when grown at 20C. A combination of these effects was observed in the double mutant recombinant. Cyanide resistant respiration was present in both mutant strains and in the recombinant at much higher levels than in the wild type strain. In the oligomycin resistant mutant, this was usually present together with cyanide sensitive respiration, whereas in the cold sensitive mutant and recombinant grown at 20C cyanide resistance approached 100%. Inhibitor and growth yield studies indicated that the cyanide resistant pathway was not used by the cold sensitive mutant during growth at 20C.