The distinct morphogenic states of Candida albicans

The human fungal pathogen, Candida albicans can grow in at least three different morphologies: yeast, pseudohyphae and hyphae. Further morphological forms exist during colony switching, for example, opaque phase cells are oblong, rather than the oval shape of yeast cells. Pseudohyphae and hyphae are both elongated and sometimes there has been little attempt to distinguish between them, as both are 'filamentous forms' of the fungus. We review here the differences between them that suggest that they are distinct morphological states. We argue that studies on 'filamentous forms' should always include a formal analysis to determine whether the cells are hyphae or pseudohyphae and we suggest some simple experimental criteria that can be applied to achieve this.