FINE STRUCTURE OF MICROORGANISMS

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Abstract
The fine structure of dormant and germinating ascospores of Saccharo-myces cerevisiae was studied by means of ultrathin sectioning and electron microscopy. Potassium permanganate proved to be a satisfactory fixative for the successful differentiation of internal structures. Structure and behavior of the nucleus, mitochondria, and various inclusions were followed during germination by cytochemical techniques as well as electron microscopy. The ascospore is surrounded by 2 coats, the inner one giving rise to the cell wall of the vegetative cell during germination. The cytoplasmic membrane was found immediately beneath the inner ascospore coat, and displayed fairly regular invaginations into the spore cytoplasm. Both the inner coat and the cytoplasmic membrane were shown to be lanthanophilic. Origin of mitochondria, and basic similarities in structure of bacterial endospores and yeast ascospores are discussed. The nature of the large vacuole regularly found in vegetative cells is also described. Evidence is presented indicating that this structure is not an integral part of the nucleus.