Use of tannic acid as a fixative-mordant to improve the ultrastructural appearance of Candida albicans blastospores.

Blastospores of Candida albicans, grown in YM broth (Difco, pH 6.0), were treated with tannic acid as part of a fixation schedule with glutaraldehyde and osmium tetroxide. The results obtained were compared to routine fixation procedures employing glutaraldehyde-osmium tetroxide and potassium permanganate, as well as several schedules using various combinations of the aforementioned fixatives. Glutaraldehyde-osmium tetroxide-tannic acid fixed cells had several morphological structures accentuated, including sharply delineated cytoplasmic and organelle membranes, a detailed cytoplasmic matrix, and an intensified layered cell wall. Tannic acid has been found to react as a mordant between osmium tetroxide and lead citrate, forming a "stabilizing matrix" within the cells. Blastospores appeared to have an improved comprehensive ultrastructural appearance, a result of the tannic acid-matrix preserving cellular components for electron microscopy.