Abstract
The DNA base composition (GC content) of 31 cultures of Debaryomyces and related yeasts including Torulaspora-type Saccharomyces was calculated from the thermal denaturation temperature (Tm) of DNA. The members of Debaryomyces and its imperfect forms exhibited GC contents from 32.4 to 45.6%, and were divided into 4 groups on the basis of this character. The first group had a GC content of 45.4-45.6%, and contained D. globosus, D. franciscae, and D. tamarii. The second group had the values of 42.4- 42.9% and consisted of D. nilssoni and 2 out of 6 strains of Torulopsis candida. The third group showed the GC values of 36.6-37.3% and consisted of D. hansenii (including D. orientalis, D. nicotianae, D. kloeckeri, and D. subglobosus), D. marama, 4 out of 6 strains of T. candida, and Candida sp. The last group had a GC content of 32.4-34.4% and consisted of D. castellii, D. cantarellii, and D. vanriji. Torulaspora-type Saccharomyces (S. rosei-T. stellata, and S. fermentati-T. colliculosa) showed GC values (42.7-43.9%) similar to those of the second group. Strains of T. candida were separated into two groups, the second and the third. This suggests the heterogeneity of D. hansenii-T. candida. Of the members of the first group, D. tamarii does not seem to be closely related to the other two species of this group on the basis of antigenic structure in spite of a close resemblance in its GC content. Therefore, 4 or 5 groups are discriminated within this genus.
