Studies on Trichophyton Tonsurans. I. The Taxonomy of T. Tonsurans

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Abstract
The history and taxonomy of Trichophyton tonsurans have been presented. Morphological studies of single spore strains of 13 recent isolates as well as of 12 named “species” have shown a varied morphological picture with regard both to colony form and microscopic structures. Serial transfers of these cultures over a two-year period have indicated, however, that none of these characteristics are stable and occur at random among the isolates. Thus the cultures studied can be considered as unstable morphological variants of a single species. Nutritional studies of these fungi, presented in detail in an earlier paper (42), had shown that there is also a close physiological similarity among these strains. All of the isolates possessed a similar partial deficiency for thiamine which gives further evidence for their identity. One strain required pyridoxine as well. It is interesting to note that hyphal fusion studies made with several members of this group by Taschdjian and Muskatblit (43) give further support to the hypothesis that many of the “species” described in the literature are synonyms of T. tonsurans. Practical applications of these morphological and physiological studies in the laboratory identification of T. tonsurans are discussed in Part II of this paper.