Size matters ? yeast petite colonie mutants

Abstract

It is well known that brewers yeast can grow by fermentation but it can also respire using mitochondria. However, damage to mitochondria can permanently block respiration. Such damaged or mutant cells can still grow, although more slowly than the wild-type, producing ?petite colonie? forms on agar plates. Remarkably, these small colonies appear spontaneously at the high frequency of 1% per generation. Indeed, petite colonie forms had frequently been observed in plated cultures of brewers or bakers yeast Saccharomyces cerevisiae by a number of groups but it was not until 1949 that Boris Ephrussi and colleagues in Paris described how these mutants differed in many properties from wild-type cells. Most saliently, they were found to lack respiration, the mutation was cytoplasmic (i.e. not associated with nuclear chromosomes), and as well as occurring spontaneously mutants could be produced in high frequency by treatment with acriflavine.