Yeast Mother Cells Research Articles

Electron microscopy of yeastlike cell development from the microconidium of Histoplasma capsulatum.

Fine details of the sequential morphological events occurring during transition of microconidia (spores less than 5 micrometer in diameter) to the yeastlike phase of Histoplasma capsulatum as seen in ultrathin section are described and illustrated by electron micrographs. Masses of microconidia were obtained when the fungas was grown on a garden soil extract medium. Spores were incubated under in vitro environmental conditions conducive for phase transition (an enriched medium at 37 degrees C). Within 48 h of incubation, the microconidia either germinated to give rise to a short mycelium or the germ tube process became a yeast mother cell without further extension. The wall of the yeast mother cell was thin and smooth, and its cytoplasmic content was ultrastructurally complex, consisting of numerous lipid bodies, vacuoles, glycogen-like deposits, and membrane systems. Within 96 h, the mother cell underwent multipolar budding to form simultaneously linear hyphal and/or ovate yeastlike daughter cells. During the transition, new cell wall materials of the germ tube, the mother cell, and yeastlike daughter cells arose by blastic action from the innermost layer(s) of the wall of the precursor form. Lomasome-like vesicles were often seen in association with areas of new cell wall formation. After organellar migration into and septation of the daughter cells, the yeast mother cell's cytoplasmic content underwent marked degenerative changes.

Cell wall replication in Saccharomyces cerevisiae.

Cell wall growth and bud formation in Saccharomyces cerevisiae was studied by labelling with fluorescent antibody. Labelled cells were grown in a glucose yeast extract broth and examined at 15-min intervals. The new cell wall was largely non-fluorescent while the old wall showed no reduction of fluorescence during growth of the bud. Bud formation was initiated as a small bulge on the cell wall, and further increase in size was accompanied by the formation of a constriction around the basal end which led to the separation of the bud from the mother yeast cell. The actively growing area of the bud was an annular band close to the base. It appears that the cell wall of the bud was, almost entirely, newly synthesized and contained very little old cell wall material. The process of wall synthesis is compared with the pattern found in several bacteria and with what is known of the process in other fungi.