1993 Volume 39 Issue 1 Pages 1-34
The presence or absence of fucose, galactose, rhamnose, and xylose as well as the ratio of glucose to mannose after hydrolysis of purified yeast cell walls are valuable characters to assign yeasts or yeast states of Ascomycetes and Basidiomycetes phylogenetically. The coupling of pellicular anion-exchange resins (Dionex CarboPac PA-1) with pulsed amperometric detection provides a simple, quick, selective, and sensitive method for the analysis of yeast cell wall carbohydrates. Phragmobasidial smut fungi of monocotyledonous (Ustilago s. str., Sporisorium) and dicotyledonous (Microbotryum, Sphacelotheca) host plants cluster in two different, phylogenetically distinct yeast types, the Microbotryum type and the Ustilago type. In contrast, all smut fungi with simple holobasidia (Entyloma, Melanotaenium) from monocots and dicots investigated so far, exhibit a cell wall carbohydrate spectrum characteristic for the Ustilago type. Ustilentyloma fluitans, although a phragmobasidial smut fungus on grasses, whose smut spores and parasitic symptoms resemble Entyloma species, display the neutral sugar pattern of the Microbotryum type. The close phylogenetic relationship between the Graphiolales, Ustilaginales s. str. (phragmobasidial smuts of monocots), and Exobasidiales was substantiated further by additional strains. The presence of xylose and balanced amounts of glucose and mannose is characteristic for yeast states of the Dacrymycetaceae. The production of extracellular amyloid compounds (EAC) as well as the cell wall carbohydrate pattern point to a Tremella type affinity of Atractogloea stillata, Itersonilia perplexans, and Sterigmatosporidium polvmorphum. A meiosporangial evolution starting from coccal yeast basidia (Sterigmatosporidium) via transversely (auricularioid) septate (Atractogloea) to longitudinally divided phragmobasidia (Tremella) and simple holobasidia (Cystofilobasidium) was substantiated further within the Tremella type. The complex holobasidia (Collybia) of the Homobasidiomycetes evolved polyphyletically from longitudinally septate phragmobasidia via partially divided holobasidia (Carcinoryces). On the basis of the cell wall carbohydrate composition of approximately 250 yeasts and yeast stages of Ascomycetes and Basidiomycetes, seven distinct yeast types are described and interpreted phylogenetically.
