Polarization optical analysis of the surface structures of various fungi

Vicinal hydroxyl groups of the sugar compounds sialic acid and 9-O-acyl sialic acid can be visualised for polarization optical analysis on the surface of different fungi using several topo-optical reactions. We investigated the presence of these molecules in cultures of Cryptococcus neoformans (heterogeneous form), Saccharomyces cerevisiae, Candida albicans, Candida glabrata, Candida krusei and Candida tropicalis by topo-optical reactions. Additionally, we examined brain and stomach tissues of patients with infections by C. neoformans and C. albicans, respectively. The results suggest a highly fashioned orientation of the sugar chains on the fungal surface. Terminal sialic- and O-acyl sialic acid residues are permanently present and orientated in a highly specific way in the cell wall of fungi. Based on the polarization optical analysis after the ABT-r (anisotropic PAS-r), the linear oriented hydroxyl groups of the sugar molecules are localized either perpendicular or parallel to the surface coat, depending on the species. According to the orientation of the vicinal hydroxyl groups, the oligosaccharide chains are orientated vertically. The capsule of the heterogeneous form of C. neoformans presented an especially strong metachromatic reaction and anisotropy. It is especially remarkable that the sterical orientation of sugar chains, and the terminal sialic acid and 9-O-acyl sialic acid molecules, was opposite in the inner and outer layer of the capsule.