THE STRUCTURES OF POLYSACCHARIDES AND GLYCOLIPIDS OF ASPERGILLUS-FUMIGATUS GROWN IN THE PRESENCE OF HUMAN SERUM

A study was made of polysaccharides and glycosphingolipids isolated fr om Aspergillus fumigatus grown in media supplemented with human serum from healthy donors. Fractionation of Cetavlon-precipitated polysaccha rides on Sephacryl S-400 gave rise to an excluded fraction (Fraction I ) with molecular weight of >400 kDa and an included peak (Fraction II) with an average molecular weight of 30-80 kDa. Fraction I comprises a bout 5% of total polysaccharide and was identified as a glycogen-like molecule. Its structure was deduced from methylation data, treatment w ith amyloglucosidase, a red brown coloration produced with an iodine s olution and by H-1 and C-13-NMR spectroscopy. It was previously sugges ted that higher amounts of glycogen-like polysaccharide (20%) were pre sent in A. fumigatus grown in serum-free medium. Fraction II was ident ified as a galactomannan and was the main polysaccharide of A. fumigat us grown in serum-supplemented medium. Its structure was elucidated ma inly by C-13-NMR spectroscopy combined with partial acetolysis and met hylation analysis. The C-13-NMR spectrum of the galactomannan showed a much greater complexity in the beta-D-galf and alpha-D-manpC-1 region s, than was evident for galactomannan from serum-free cultures previou sly described, reflecting differences in the glycosylation pattern, st imulated in serum-supplemented medium. No differences in A. fumigatus glycosphingolipid could be detected between serum-containing and serum -free growth conditions. Our results demonstrate that the change in po lysaccharide structure is a more specific response to the altered grow th conditions and not merely a symptom of more general changes.