SIGNIFICANCE OF DNA BASE COMPOSITION IN THE CLASSIFICATION OF YEAST GENUS SACCHAROMYCES

Abstract

DNA base composition (GC content) of 84 cultures of Saccharomyces and related yeasts was investigated. Saccharomyces yeasts employed in the present experiment showed the GC content from 32.4 to 45.9%. the range of which was about 13%. Three groups having GC values of 32.4-33.7%, 38.3-40.7%, and 42.7-45.9% were recognized, and most of the species had a GC content of 40% or so. Of the four groups discriminated by VAN DER WALT, the two (the first and third groups) were considered to be natural taxonomic groups on the basis of GC content. The first group (Saccharomyces sense stricto) had a GC value of 38.3-40.7% with a small range of variation of 2.4%. This group is homogeneous also in serological characteristics investigated by TSUCHIYA and his co-workers. Members of the third group showed a GC value of 42.7-43.4% except S. florentinus and S. microellipsodes. As far as is known, this group (with two exceptions mentioned above) is also homogeneous in serological characteristics. It is considered that it would be better to separate this group from Saccharomyces as Torulaspora. S. florentinus and S. microellipsodes would be better included in the first group or in the second.