Mitochondrial DNA
Mitochondrial DNA was discovered in the 1960s by Margit M. K. Nass and Sylvan Nass by electron microscopy as DNase-sensitive threads inside mitochondria, and by Ellen Haslbrunner, Hans Tuppy and Gottfried Schatz by biochemical assays on highly purified mitochondrial fractions.
Microsporum nanum
Mitochondrial DNA sequences have been used for phylogenetic studies in the dermatophytes. A typical fungal mitochondrial DNA usually contains 14 conserved protein-coding genes, 22 to 26 tRNA gene, and 2 rRNA genes. The difference of mitochondrial DNA between fungal species is due to the variations in intergenic region, intron, and gene order. The complete sequences of "Trichophyton rubrum", "T. mentagrophytes", "T. ajelloi", "M. canis", "M. nanum", and "Epidermophyton floccosum" show that these 6 species in dermatophytes are closely related because their mitochondrial genomes are highly conserved. Genome size of mitochondrial DNA in "M. nanum" is 24,105 basepairs. The DNA is AT-rich and the GC content is only 24.47%. "M. nanum" mtDNA has 15 protein-coding genes, including ATP synthase subunits "atp6", "atp8", and "atp9", cytochrome oxidase subunits "cox1", "cox2", and "cox3", apocytochrome b "cob", a ribosomal protein "rps5", and NADH dehydrogenase subunits "nad1", "nad2", "nad3", "nad4", "nad5", and "nad6". The gene order of the 15 conserved protein coding genes in "M. nanum" mtDNA is identical to that of "T. rubrum", "T. mentagrophytes", "T. ajelloi", and "M. canis". The "Microsporum nanum" mtDNA also contains 2 rRNAs and 25 tRNAs. In addition, this mitochondrial genome is highly compact because 83.76% are structural genes. Moreover, the genome contains one intron and one intronic ORF.