Abstract

This study was aimed at determining the effect of the glycolytic inhibitor, sodium fluoride(NaF), on induced yeast cells. Rhizopus stolonifer was cultivated in synthetic broth for 120 h, at pH 4.5 and ambient temperature of 28 ± 1°C, using sporangiospores as inoculum.Growth was in discrete units, which were sedimented. Microscopic examination revealed induction of neoplasts, protoplasts and yeast cells, but biomass profiles (OD, 625nm) did not exhibit sigmoid pattern in control or glycolytic inhibitor-NaF incorporated broths. A two-way analysis of variance showed that NaF and its interaction with time significantly affected growth (p < 0.05). Means separation was into three subsets, with 20 mM (subset 1) having the highest biomass and least occurred at 5 mM, which was comparable to 30 mM, control and 10 mM (subset 3). A further study revealed effect of application time ofNaF at two levels (20 and 10 mM) on morphological expression. Three main effects were observed: (a) complete inhibition of yeast induction, (b) delayed induction of yeast cellsand (c) apoptosis of induced yeast cells. In the complete absence of yeast cells, protoplasts were copiously produced. However, when yeast cells were induced prior to NaF challenge, the inhibitor caused death of cells. Hence, it was suggested that induction of terminal budding yeast cells was closely associated with glycolysis. Further studies are recommended in order to examine the contribution of individual inductive enzymesincluding those of glycolysis, during the transformation process.

Key words: Rhizopus stolonifer, sporangiospores, protoplasts, yeast induction, sodium fluoride, apoptosis.