Phenotypes of Candida albicans sterol mutants deficient in delta 8,7-isomerization or 5-desaturation

Two Candida albicans sterol mutants deficient in delta 8,7-isomerization and 5-desaturation, respectively, were studied in relation to those phenotypes associated with the 14 alpha-demethylation deficiency, i.e. repression of hypha formation, inability to grow with non-fermentable substrates, and increased sensitivity to nonpolyene-nonazole chemicals. It was found that the delta 8,7-isomerization deficiency, resulting in the accumulation of delta 8 sterols (mostly delta 24(28) or delta 5,22), was associated with severe reduction in hyphal growth and utilization of non-fermentable substrates. These cellular activities were reduced only slightly when 5-desaturation was deficient, causing the accumulation of delta 7 sterols. On the other hand, both the isomerization and desaturation deficiencies were accompanied by multiple increases in drug sensitivity which were small in magnitude compared with those associated with the 14 alpha-demethylation deficiency.