Morphological changes in ascospores of Saccharomyces cerevisiae during aerobic and anaerobic germination.

Abstract

The stainability of ascospores and vegetative cells of Saccharomyces cerevisiae to acid-fast staining, using hot Ziehl's carbolic fuchsin solution, 5 % sulfuric acid, and diluted Lofer's methylene blue, was examined. Resting spores and growing haploid cells (a type strain 24428 and a type 3626) retained much fuchsin dye in the cells. Only mature spores of diploid G2-2 resisted methylene blue staining. The stainability of Mycobacterium phlei IFO 3158 also examined. The kinetics of germinationn were examined. The loss of the stainability with acid-fuchsin and of the resistance to methylene blue was used as a criterion of germination. The ascospores germinated anaerobically as well as aerobically. Especially in the early stage of germination, there was found no difference in the germination rates under both conditions. Ultrastructure of germinating ascospores cultured in aerobic and anaerobic conditions was examined by ultrathin sectioning and electron microscopy. At the first stage of germination, the ascospores swelled in aerobic as well as anaerobic cultures. The outer spore coat and the outer zone of inner spore wall disappeared during the germination process, the inner zone of the spore wall then giving rise to a germinated spore cell wall (=extruded germ tube wall). The vacuole became granular. The mitochondria showed no change in shape and number in aerobic cultures, but seemed to swell and disintegrate in the later stages of anaerobic germination.

Double staining of mitochondria and mitochondrial nucleoids in the living yeast during the life cycle.

“…Although it has been known that the germination can occur in the absence of respiration and a functional mitochondrial genome (21), our results suggest that the activation of respiration occurred at the beginning of germination under aerobic condition. The results also coincided with the electron-microscopic observations that showed the development of mitochondrial cristae after the first hour in germination medium (16).…”

Involvement of actin and polarisome in morphological change during spore germination of Saccharomyces cerevisiae

“…Morphologically, spore germination is a relatively simple process to allow outgrowth from a spore. Therefore, only a limited number of researchers have investigated the change of cell shape during germination (Hashimoto et al , 1958; Palleroni, 1961; Kreger‐Van Rij, 1978; Sando et al , 1980). Compared with spore germination, the morphological changes during vegetative growth have been intensively studied.…”

Carbohydrate Metabolism during Sporulation in Spheroplasts of Yeast,Saccharomyces cerevisiae

“…Chitin or a chitin-like polymer is a structural component of the outer layers of the spore wallY·18. 19) The accumulation of the polymer began prior to the appearance of prespores and was completed within the period of spore formation. The results of chemical analyses and fluorescence microscopic observation suggested that the outermost surface of the chitin layer of the prespore wall might be covered with another substance(s), that prevents the chitin from binding with an added chitin-specific fluorescent dye during spore maturation.…”