Why is it when one performs sequencing or some other form of biological identification of a fungus, that the fungus identifies as some sort of "teleomorph"? For example, if I'm growing up a yeast that I suspect is Cryptococcus neoformans, and I sequence it to be sure, why is it that the sequence becomes homologous to "Filobasidiella neoformans"? I will then search Filobasidiella neoformans, and all searches will tell me that Filobasidiella IS Cryptococcus! Why are there multiple names for the same thing? Another example: Arthroderma benhamiae and Trichophyton mentagrophytes. Blastomyces dermatitidis and Ajellomyces dermatitidis. It is SO CONFUSING!
TestAmerica Expert: Ariunaa Jalsrai
Expert's Response:
Phylogenetic methods require sufficient quantities of biological materials (spores or fresh specimens) that are from pure (i.e., uncontaminated) fungal cultures, for many asexual species their exact relationship with other fungal species has yet to be determined. Under the current system of fungal nomenclature, teleomorph (the sexual reproductive stage of fungi, typically a fruiting body) names cannot be applied to fungi that lack sexual structures. Classifying and naming asexually reproducing fungi is the subject of ongoing debate in the mycological community. The DNA sequences derived from teleomorphic materials will not always be identical to those sequences derived from anamorphic materials of the same species, due to the recombination of DNA in teleomorphs as one possible reason for DNA sequence divergence. Thus, it is important to first investigate the nucleotide sequence diversity between the DNA derived from teleomorphic and anamorphic materials in order to study the phylogenetic relationships of fungi.
Cryptococcus neoformans, the agent of cryptococcosis, had been considered a homogeneous species until 1949 when the existence of four serotypes was revealed based on the antigenic properties of its polysaccharide capsule. Such heterogeneity of the species, however, remained obscure until the two morphologically distinct teleomorphs of C. neoformans (Filobasidiella neoformans and Filobasidiella bacillispora) were discovered during the mid 1970s. Based on the genetic characteristics and serologic properties of capsular polysaccharides, three varieties and four nonhybrid serotypes have been defined, namely, C. neoformans var. neoformans (serotype D), C. neoformans var. grubii (serotype A), and C. neoformans var. gattii (serotypes B and C). Serotypes correspond to different sexual teleomorphs, namely, Filobasidiella neoformans and Filobasidiella bacillispora for serotypes A and D and serotypes B and C, respectively.
In your case, I think you are dealing with Cryptococcus neoformans hybrid serotype AD, which is teleomorph Filobasidiella neoformans.
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