Scanning electron microscopy of the development of structured aerial mycelia and satellite colonies of phenotypically switched Candida albicans

Candida albicans is an asexual diploid fungus that can express high frequency phenotypic switching. Switched variants can develop structured aerial mycelia (SAM) and cultures that have been grown for a protracted period exhibit satellite colonies. This study investigated the development of both SAM and satellite colonies by means of a freeze-drying technique and scanning electron microscopy. The results show that SAM may develop due to hyphae developing in the colony at the base of the structures. The development of satellite colonies is a result of cells that have grown deep into the agar re-emerging on to the agar/air surface and producing a new colony. Although both SAM and satellite colonies are often seen together on mature colonies, their cause and development are different.