Serological classification of the genus Saccharomyces. (3)

Fungal polysaccharides

Fungal polysaccharides are cell wall components which may act as antigens or as structural substrates. As antigens, the role of mannans in Saccharomyces cerevisiae and Candida albicans, and of glycoproteins in Aspergillus fumigatus are discussed. Analyses on beta-glucan synthetase in Paracoccidioides brasiliensis and the inhibitory effect of Hansenula mrakii killer toxin on beta-glucan biosynthesis are also considered.

Immuno-assay techniques for detecting yeasts in foods

A brief literature review on immuno-assay of yeast cell wall antigens is given. Special attention is paid to extracellular, thermostable yeast antigens (EPS), which are released to the growth medium by many yeast species. The EPS of Saccharomyces cerevisiae and of Stephanoascus ciferrii (syn. Candida ciferrii) could be specifically and sensitively detected by a sandwich ELISA, using an IgG raised in rabbits immunized with the EPS of these yeasts. The EPS ELISA of three basidiomycetous yeasts tested was not specific, that of Geotrichum candidum was genus-specific but was not sensitive. The EPS of Zygosaccharomyces bailii could be detected in a highly specific competitive ELISA but not in a sandwich ELISA or in a latex agglutination test.

Reassessment of antigenic determinant of Saccharomyces cerevisiae serotype Ia

We examined the immunochemical structure of the antigenic determinant of S. cerevisiae serotype Ia. The specific factor serum for S. cerevisiae serotype Ia was obtained either from factor 18 serum by adsorption with heat-killed cells of Candida glabrata, or from anti-S. cerevisiae Ia (M 6001) serum by adsorption with heat-killed cells of S. cerevisiae Ib (IFO 0751). We designated this adsorbed serum as factor 18a. Acetolysis of S. cerevisiae cell wall D-mannan gave five oligosaccharides. Signals of 1H-nuclear magnetic resonance spectra of mannooligosaccharides derived from S. cerevisiae mannan were assigned for their linkages by the aid of those of alpha-1,3'-linked mannooligosaccharides derived from glucuronoxylomannan of capsule of Cryptococcus neoformans serotype A-D. Agglutination-inhibition experiments revealed that the mannopentaose from S. cerevisiae mannan was the most effective inhibitor. Moreover, inhibitory activities of alpha-1,3'-linked mannotriose, mannotetraose, and mannopentaose which were derived from glucuronoxylomannan of C. neoformans were shown to be higher than those of mannotetraose with one terminal alpha-(1-3) linkage from homologous S. cerevisiae mannan. These results indicate that mannopentaose with terminal two alpha-(1-3) linkages is responsible for the specificity of S. cerevisiae Ia.

Immunological separation of Entomophthorales genera

Exoantigens from Erynia neoaphidis, Conidiobolus major, C. thromboides, C. obscurus, Zoophthora radicans, and Basidiobolus ranarum were obtained from culture filtrates of fungal material grown in a yeast extract, peptone dialysate, dextrose medium and were tested against specific hyperimmune antisera prepared from E. neoaphidis, C. major, C. thromboides, and B. ranarum by the immunodiffusion technique. Specific precipitins were observed for E. neoaphidis and B. ranarum, while cross-reactions were detected among C. major, C. thromboides, and C. obscurus. The results suggest that genera of Entomophthorales can be easily separated by this simple immunological procedure.

DNA base composition of species of the genus Saccharomyces

DNA base compositions (GC content) of Saccharomyces species are reported and discussed. Several amendments of the four groups given by van der Walt are suggested, viz. the transfer of S. kluyveri to group 1, and of S. eupagycus, S. cidri, S. montanus, S. microellipsodes and S. florentinus to group 2. The synonomy of S. amurcae and S. cidri is suggested. The DNA base compositions revealed two possible pairs of sibling species: S. elegans and S. bailii, with a difference in GC content of 4.1%; S. dairensis and S. servazzii with a difference in GC content of ca. 3%. S. mrakii had a GC content of 47.3-48.5% the highest encountered in this genus and similar to that of Kluyveromyces thermotolerans.