Mitochondrial Structure

Abstract

INTRODUCTION
The study of the structure and organization of mitochondria in Saccharomyces cerevisiae offers a unique opportunity to relate the considerable metabolic, genetic, and biochemical data on this organism to visible morphological entities. The ability of yeast to thrive under a variety of growth conditions permits their mitochondria to exist in a wide range of functional states and to maintain genetic deficiencies that would otherwise be lethal to an organism. In many cases, these functional states and mutations have their morphological counterpart in defined fine structural modifications of the mitochondrial population. In addition, the complex interaction of the nuclear and mitochondrial genomes in the formation of mitochondria can be dissociated in yeast by making use of ρ⁻ strains, which lack a functional mitochondrial genome and thus allow the contribution of the nuclear genome to be visualized directly.

TECHNIQUES OF PREPARATION
Although there are favorable aspects of yeast as an organism for the study of mitochondrial structure, an inherent and major difficulty lies in its rigid and impermeable cell wall. This wall, which enables yeast to survive drastic growth conditions, is a definite impediment to the standard preparation procedures for electron microscopy. The penetration of fixatives, notably osmium tetroxide, and the infiltration of embedding media are hindered, if not completely blocked, by the wall. To overcome this handicap, one may resort to the use of chemical fixatives that penetrate more readily, such as potassium permanganate. Alternatively, one may weaken or completely remove the cell wall by using digestive enzymes to allow...