Candida albicans fungus, coloured scanning electron micrograph (SEM). Candida albicans is a pathogenic yeast that commonly occurs in the normal human gut. It can become pathogenic and cause health problems in individuals with an immunodeficiency (such as organ transplant recipients and people with AIDS or leukaemia), causing candidiasis, which results from an overgrowth of the fungus. Magnification: x8000, when printed 15cm wide.