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BEST: Barcode Enabled Sequencing of Tetrads
Published on: May 1, 2014
ITS barcodes for Trichophyton tonsurans and T. equinum
Richard C Summerbell1, Mary K Moore, Mieke Starink-Willemse
1CBS Fungal Biodiversity Centre, Utrecht, the Netherlands. summerbell@cbs.knaw.nl
Medical Mycology
|April 28, 2007
Summary
This study clarifies the taxonomy of dermatophytes Trichophyton equinum and Trichophyton tonsurans. New ribosomal internal transcribed spacer (ITS) sequencing resolves identification issues caused by older sequence errors, establishing clear ITS barcodes for these species.
Area of Science:
- Medical Mycology
- Molecular Systematics
- Population Genetics
Background:
- Early molecular studies caused confusion in dermatophyte taxonomy, specifically for Trichophyton equinum and Trichophyton tonsurans.
- Routine identification using ribosomal internal transcribed spacer (ITS) sequences was impractical due to ambiguous data in GenBank.
- Recent clarification of taxonomic status necessitates reliable molecular identification methods.
Purpose of the Study:
- To resolve taxonomic ambiguities between Trichophyton equinum and Trichophyton tonsurans using ITS sequencing.
- To establish standardized ITS 'barcode sequences' for accurate identification of these dermatophyte species.
- To investigate an Asian genotype and discuss the population genetics of T. equinum var. autotrophicum.
Main Methods:
- Resequencing of internal transcribed spacer (ITS) regions from anomalous dermatophyte isolates.
- Analysis of newly generated and existing GenBank sequences for T. equinum and T. tonsurans.
- Designation of a taxonomic neotype for Trichophyton equinum.
Main Results:
- Resequencing eliminated previous identification problems stemming from read errors in older sequences.
- Trichophyton equinum exhibits uniform ITS sequences globally; T. tonsurans is also uniform with a minor variation in one strain.
- A distinct Asian genotype was identified, requiring further classification, and T. equinum var. autotrophicum was confirmed as closely related to T. equinum var. equinum.
Conclusions:
- Standardized ITS barcode sequences are proposed for T. tonsurans and T. equinum, enabling reliable routine identification.
- The study provides a stable taxonomic anchor for T. equinum through neotype designation.
- Population genetics provides context for the unusual phenotype of T. equinum var. autotrophicum.
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