Saccharomyces barnetti and Saccharomyces spencerorum: two new species of Saccharomyces sensu lato (van der Walt).

In the course of a study of DNA base sequence homology, 19 strains labelled as Saccharomyces exiguus, its imperfect state, Candida holmii, or C. milleri were examined. Results confirmed the separation of C. milleri as a separate species. The remaining strains can be divided into three distinct groups of genomic relatedness. The type cultures of S. exiguus and C. holmii form a cluster with 10 other strains showing variable reassociation values ranging from 100 to 40%. The remaining four strains comprise two separate species showing no nucleotide relatedness between themselves nor to either the S. exiguus complex or to C. milleri. Physiological analyses demonstrate that it is possible to separate these four taxa on the basis of a few simple tests. The two new species are described respectively as Saccharomyces barnetti honoring James Barnett in recognition of his invaluable work in the field of yeast taxonomy and Saccharomyces spencerorum in honor of J.F.T. and Dorothy M. Spencer who have made innumerable contributions to the genetics and biotechnological application of yeasts.