ABSTRACT
The identification of filamentous fungi has always been considered difficult and many misunderstandings and misidentifications can bee found in the literature (Frisvad 1989; Mantle 1987). Phenotypic characters, e.g., morphology and growth on selected media have traditionally formed the basis for fungal taxonomy (Domsch et al. 1980; Mantle 1987; Pitt 1979; Raper and Fennell 1977; Raper and Thom 1949). Advancements in the developments of analytical methodology have allowed the use of “secondary” metabolite profiling for fungal identification and been used to revise the taxonomy within genera of Penicillium, Aspergillus, Fusarium, Alternaria, and their perfect states. The success of metabolite profiling in the classification of filamentous fungi relies on the fact that a major part of the fungal growth is expressed by the production of numerous diverse metabolites, most of which are excreted into the media. The extracellular metabolites have been termed the exome, a subgroup of the metabolome (all metabolites), and these are related to the genome as illustrated in Figure 1. The reasons why most filamentous fungi produce such a diverse profile of secondary metabolites are still unclear, but they are probably produced as a result of stimuli and are directed against, or support actions on, receptor systems (Christophersen 1996) or as outward directed (extrovert) differentiation products. Possible others functions, include chemical signaling between organisms (Christophersen 1996; Frisvad 1994a). Williams et al. (1989) described their functions as “…serve the producing organisms by improving their survival fitness… .”
