Mitochondrial integrity and maltose utilization in yeast

Strains of the yeast Saccharomyces cerevisiae able to utilize maltose only in the presence of functional mitochondria have been described. Two such strains Z104-4B and Z109-1C were isolated as revertants from parental strains unable to utilize maltose. These strains are unique in the sense that although they produce inducible maltase for normal growth on maltose agar plates in the presence of functional mitochondria, they are very poor fermenters of maltose under anaerobic condition. Glycerol negative mutants isolated from these strains simultaneously lose the ability to utilize maltose. One of the manganese induced glycerol negative mit- mutants Z104-4B-Mn1, reverts concomitantly to growth on glycerol and maltose agar plates. On the basis of results presented in this paper, we propose the possibility of existence of two alternate mechanisms for maltose utilization in yeast. An oxidative mechanism for which mitochondrial functions are indispensable, and a fermentative pathway for which mitochondrial integrity is not required.