rRNA gene internal transcribed spacer 1 and 2 sequences of asexual, anthropophilic dermatophytes related to Trichophyton rubrum

Abstract

The ribosomal region spanning the two internal transcribed spacer (ITS) regions and the 5.8S ribosomal DNA region was sequenced for asexual, anthropophilic dermatophyte species with morphological similarity to Trichophyton rubrum, as well as for members of the three previously delineated, related major clades in the T. mentagrophytes complex. Representative isolates of T. raubitschekii, T. fischeri, and T. kanei were found to have ITS sequences identical to that of T. rubrum. The ITS sequences of T. soudanense and T. megninii differed from that of T. rubrum by only a small number of base pairs. Their continued status as species, however, appears to meet criteria outlined in the population genetics-based cohesion species concept of A. R. Templeton. The ITS sequence of T. tonsurans differed from that of the biologically distinct T. equinum by only 1 bp, while the ITS sequence of the recently described species T. krajdenii had a sequence identical to that of T. mentagrophytes isolates related to the teleomorph Arthroderma vanbreuseghemii.

FIG. 1

Map of the rDNA regions sequenced in this study and descriptions of PCR and sequencing primers. (A) Target sites of the primers on the rDNA map. Forward primers are shown above the map, and reverse primers are shown below it. (B) Sequences of the primers.

FIG. 2

Aligned rDNA sequences of Trichophyton and Arthroderma species. Abbreviations: A. vanbreusegh., A. vanbreuseghemii; T. mentagroph., T. mentagrophytes. The symbols + and − designate mating types, as shown in Table 1. T. mentagrophytes has two sequence types, here designated as T. mentagroph.1 and T. mentagroph.2, exemplified by strains UAMH 8543 and 7339, respectively. Positions 295 to 296, 325 to 329, 339, 386, 389, 639, 641 to 643, 754 to 761, 763, 765, 767, 769, and 771 of this alignment were determined to contain ambiguously aligned nucleotides and were not included in phylogenetic analyses.

FIG. 2

Aligned rDNA sequences of Trichophyton and Arthroderma species. Abbreviations: A. vanbreusegh., A. vanbreuseghemii; T. mentagroph., T. mentagrophytes. The symbols + and − designate mating types, as shown in Table 1. T. mentagrophytes has two sequence types, here designated as T. mentagroph.1 and T. mentagroph.2, exemplified by strains UAMH 8543 and 7339, respectively. Positions 295 to 296, 325 to 329, 339, 386, 389, 639, 641 to 643, 754 to 761, 763, 765, 767, 769, and 771 of this alignment were determined to contain ambiguously aligned nucleotides and were not included in phylogenetic analyses.

FIG. 2

Aligned rDNA sequences of Trichophyton and Arthroderma species. Abbreviations: A. vanbreusegh., A. vanbreuseghemii; T. mentagroph., T. mentagrophytes. The symbols + and − designate mating types, as shown in Table 1. T. mentagrophytes has two sequence types, here designated as T. mentagroph.1 and T. mentagroph.2, exemplified by strains UAMH 8543 and 7339, respectively. Positions 295 to 296, 325 to 329, 339, 386, 389, 639, 641 to 643, 754 to 761, 763, 765, 767, 769, and 771 of this alignment were determined to contain ambiguously aligned nucleotides and were not included in phylogenetic analyses.

FIG. 2

Aligned rDNA sequences of Trichophyton and Arthroderma species. Abbreviations: A. vanbreusegh., A. vanbreuseghemii; T. mentagroph., T. mentagrophytes. The symbols + and − designate mating types, as shown in Table 1. T. mentagrophytes has two sequence types, here designated as T. mentagroph.1 and T. mentagroph.2, exemplified by strains UAMH 8543 and 7339, respectively. Positions 295 to 296, 325 to 329, 339, 386, 389, 639, 641 to 643, 754 to 761, 763, 765, 767, 769, and 771 of this alignment were determined to contain ambiguously aligned nucleotides and were not included in phylogenetic analyses.

FIG. 2

Aligned rDNA sequences of Trichophyton and Arthroderma species. Abbreviations: A. vanbreusegh., A. vanbreuseghemii; T. mentagroph., T. mentagrophytes. The symbols + and − designate mating types, as shown in Table 1. T. mentagrophytes has two sequence types, here designated as T. mentagroph.1 and T. mentagroph.2, exemplified by strains UAMH 8543 and 7339, respectively. Positions 295 to 296, 325 to 329, 339, 386, 389, 639, 641 to 643, 754 to 761, 763, 765, 767, 769, and 771 of this alignment were determined to contain ambiguously aligned nucleotides and were not included in phylogenetic analyses.

FIG. 2

Aligned rDNA sequences of Trichophyton and Arthroderma species. Abbreviations: A. vanbreusegh., A. vanbreuseghemii; T. mentagroph., T. mentagrophytes. The symbols + and − designate mating types, as shown in Table 1. T. mentagrophytes has two sequence types, here designated as T. mentagroph.1 and T. mentagroph.2, exemplified by strains UAMH 8543 and 7339, respectively. Positions 295 to 296, 325 to 329, 339, 386, 389, 639, 641 to 643, 754 to 761, 763, 765, 767, 769, and 771 of this alignment were determined to contain ambiguously aligned nucleotides and were not included in phylogenetic analyses.

FIG. 3

Phylogenetic relationships of Arthroderma and Trichophyton species inferred from nucleotide sequences of the rDNA ITS1 and ITS2 regions and 5.8S gene. This unrooted phylogram is the consensus of the two most parsimonious trees (72 steps; consistency index = 0.944, retention index 0.971) found by a search conducted in PAUP 3.0 using the branch and bound method. Values above the branches are the total nucleotide changes assigned by the analysis, and values below the branches are the percentages of 1,000 bootstrap analysis replicates in which the branches occurred.