Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Protein electrophoresis was employed to see if it would give some insight into the taxonomic question of delineating species in the yeast genus Kluyveromyces van der Walt emend. van der Walt.;The type strains of the species of the geneus Kluyveromyces sensu van der Walt (1970) were compared for eleven isoenzymes. These enzymes included five oxidoreductases, five hydrolases, and one lyase.;The isoenzyme patterns of of seven enzymes of Kluyveromyces populations from a variety of habitats were compared. The isolates belonged to the Kluyveromyces lactis and K. marxianus deoxyribonucleic acid (DNA) reassociation groups, and to Kluyveromyces dobzhanskii, Kluyveromyces thermotolerans, and Kluyveromyces waltii.;The results of multivariate analysis of the electrophoretic patterns supported the division of the genus into thirteen species, two of which comprised four and five taxa (described by van der Walt, 1970b) respectively. Electrophoretic data were at variance with in vitro mating compatibility patterns but supported DNA-DNA reassociation data.;Finally, interspecific and intraspecific hybrids between K. marxianus and K. thermotolerans and between K. lactis and K. vanudenii, respectively, their parental strains, and their corresponding type cultures were studied by comparison of seven isoenzyme patterns. The parental strains of the interspecific hybrid were very different, and crossing between these two strains did not receive much direct substantiation. The K. marxianus x K. thermotolerans hybrid appeared very similar, electrophoretically, to its K. marxianus parental strain, and had little in common with K. thermotolerans. The loss and gain of bands by the hybrid strain did support Kurtzman's et al. (1983) suggestion that it might be an aneuploid yeast. Even though the parental strains of the intraspecific hybrids had very similar isoenzyme patterns, differences in electrophoretic patterns were observed between parental and hybrid strains, indicating that crossing can occur between K. lactis and K. vanudenii. Certain isoenzymes were found to be better indicators of the hybrid state than other enzymes. The possible relationships between hybrids and populations were explored.



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