General Characteristics of Fungi
The fungi are eukaryotic, heterogeneous, unicellular to filamentous, spore bearing, and chemoorganotrophic organisms which lack chlorophyll. The fungi have three major morphological forms, i.e. unicellular yeast, filamentous mould (mold) and yeast-like form (pseudohyphae form). The dimorphic fungi (Blastomyces dermatitidis, Coccidioides immitis, Histoplasma, Sporothrix schenckii) are able to produce both the forms (yeast and mould) depending on the temperature (thermal dimorphism). The yeast form is produced within the body of the host (in vitro at 37 °C) and the mould form is observed either in the environment or in artificial culture medium (at room temperature). The pseudohyphae form is chains of elongated ellipsoidal cells with constriction between them and it is produced by Candida albicans.