The "morphology index" - an objective measurement of cell shae in Candida albicans.

The "morphology index" an objective measurement of ceil shape in Candida albicans. Louise A. Merson-Davies. The morphology of the fungus Candida albicans was characterised by measurement of cell dimensions with the aid of computerised image analysis. The dimensions were used to calculate a mathematical ratio, the morphology index, which fell in the range 1 to 4.5. Spherical yeast cells gave low Mi values, whilst true hyphal cells gave Mi values greater than 3.2. This study shows that Mi can be used reliably in the place of subjective descriptions of C. albicans morphology. The mean Mi of a cell population varied according to the growth environment and the strain of C. albicans. Mi was found to reveal a continuum of morphologies in C. albicans cells both in vitro and in vivo, with no clear relationship observed between cellular morphology and the pathogenic status of C. albicans. Chemical and cellular analyses were performed on a variety of morphological forms of C. albicans, as determined by Mi. The chitin content of C. albicans cells increased linearly with Mi, although no significant correlation was found between the activity of the polysaccharide degradation enzymes, chitinase and glucanase, and morphology. Autoradiography and analysis of cell wall expansion suggested that the apex of the cell was the main region of expansion, regardless of morphology. General wall expansion was found to be repressed in cells with Mi greater than 2. The rate of overall cell wall expansion increased linearly with Mi. Investigations with "hypha-specific" monoclonal antibodies indicated a correlation between antibody reactivity and Mi, epitope expression appeared to be induced in cells with Mi greater than 3. The linear relationship observed between some properties (polysaccharide composition and overall wall expansion) and Mi suggests that quantitative regulation mechanisms may determine cell morphology.