The genus Saccharomyces (Meyen) Reess

The speciesSaccharomyces heterogenicus Osterwalder,Saccharomyces steineri Lodder et Kreger-van Rij,Saccharomyces pastorianus Hansen,Saccharomyces bayanus Saccardo andSaccharomyces willianus Saccardo were compared. It was found that the biochemical characters used for the definition of these species were variable and the strains of the given species were therefore evaluated together. With reference to the present accepted criteria of species specificity, grouping on the basis of coefficients of similarity was not conclusive. One of the characters (the fermentation and assimilation of galactose) was therefore dispensed with, while a new characteristic (determination) of amylolytic activity was added. It was found that the speciesSaccharomyces pastorianus, Saccharomyces bayanus andSaccharomyces willianus were so similar that they could be grouped in one species.Saccharomyces heterogenicus retained its species specific characteristics, whileSaccharomyces steineri formed a transition between this species and the other three. The coefficients of similarity, S, calculated by the methods of Jaccard and of Sokal and Michener, were compared and some of the more problematical questions of the numerical method are discussed.