ABSTRACT
Yeasts are traditionally characterized, classified, and identified by morphological and physiological criteria (Kreger-van Rij, 1987; Kurtzman and Fell, 1998). Since the 1970s, a large amount of data on the chemical composition of cell walls, capsular polysaccharides, whole-cell hydrolysates, antigenic determinants, and enzyme patterns have provided valuable information for yeast taxonomy (Phaff, 1984). However, the most important criteria for classification are DNA base composition, nuclear DNA(nDNA) homology, and the sequences of ribosomal DNAmolecules, which can be used not only to elucidate the degree of relatedness but also to reveal evolutionary relationships of yeasts (Kurtzman and Phaff, 1987; Wilmotte et al., 1993; Kurtzman and Robnett, 1998). Sophisticated biochemical and molecular methods, however, cannot be easily applied in routine identification procedures. Hence, in both classification and identification of yeasts, the morphological and physiological criteria, among them the characteristics of sexual reproduction, are still important (von Arx and van der Walt, 1987; Yarrow, 1998; Boekhout and Phaff, 2003) (Table 1.1).
