Morphology of Yeast Mitochondria

Abstract

THERE has recently been some controversy as to the possibility of demonstrating other than granular mitochondria of yeast cells^1–3. It is well known that for a long time the only mitochondria that cytologists were able to demonstrate in yeast cells were round, granular structures. As their minute dimensions make it practically impossible to observe the same cell before and after treatment with fixatives, stains, etc., the identification of yeast mitochondria must necessarily be doubtful. However, knowledge of the structure of the living cell, and the comparison of cytochemical results with the state of the living untreated cell, should be good safeguards against incorrect interpretation. One frequently abstains from using phase-contrast when examining yeast cells because, under the usual conditions of examination, cells of the yeast type which have a high solid content and refractive index give unsatisfactory images⁴. The fact that incomparably better results can be obtained with phase-contrast, provided immersion media of suitable refractive index are used, was stressed in Britain by Barer et al. ⁵, and this principle has been used by us for the study of micro-organisms, notably yeast cells.