Fat Production by Inositol-deficient Yeast

Abstract

THE growth of a yeast (Saccharomyces cerevisiae) and a bacterium in mixed culture in a defined medium containing an abnormally low concentration of growth factors has been studied by Challinor and Rose¹, who observed a number of inter-relationships between the two organisms under these conditions. During the continuation of this work, growth of the yeast in a medium in which the concentration of a single growth factor (inositol) was reduced below the normal level was studied, and interesting changes in the morphological and physiological characters of the yeast were observed. Thus, microscopical examination revealed that the deficient cells formed large aggregates and were more granular than normal cells. These differences were clearly seen after two days growth and became more marked during further incubation. After about three days, the deficient cells were obviously unhealthy in appearance and were easily ruptured, for example, by pressing the coverslip lightly once only. The ease with which rupturing took place increased on further incubation, and after five days very little pressure indeed was required to release the cell contents. A large part of the material so released was oily in nature, and the small droplets coalesced to form large globules which gave typical staining reactions for fats when treated with sudan III and with osmic acid. Normal cells behaved very differently, considerable pressure being required to cause rupture, and then only a proportion of the cells were broken, releasing very little fatty material.