A study on stability of phenotype and genotype of Trichophyton rubrum.
OBJECTIVE
To explore the stability of phenotype and genotype in Trichophyton rubrum.


METHODS
All the strains were cultured on Sabouraud's dextrose agar slopes, and identified to species level. Strains isolated recently were subcultured on Sabouraud agar slopes four times at an interval of 4 weeks. DNA was extracted with CTAB method. A probe consisting of 3' end of 18S rDNA, adjacent ITS1, 5.8S rDNA and ITS2 regions was amplified from template DNA of the T. rubrum standard strain using fungal universal primers NS5 and ITS4, labelled by P32 and hybridized with EcoR I-digested T. rubrum genomic DNA.


RESULTS
(1) Four phenotypes were isolated from 207 T. rubrum strains, with downy type (45.4%) in the first place, and granular type not found. After 1 year of conservation, 54 strains showed morphological variations with the total variation rate of 26.1%. (2) Eleven strains showed variations in colony morphology or pigment upon subculture. (3) AP-PCR analysis of 10 T. rubrum isolates and one T. rubrum standard strain showed similar DNA patterns with main bands at 2.2, 1.7, 1.3, 0.9 and 0.7 kb. No changes in DNA pattern were found upon subculture. (4) Hybridization analysis revealed that all the 11 T. rubrum strains presented three bands and were identified into two types (2.4, 3.9, 5.9 kb and 2.4, 4.4, 6.5 kb). No changes in band pattern were found upon subculture.


CONCLUSIONS
Phenotype of T. rubrum was instable and the colonial morphology and pigment easily changed during conservation or subculture, while its genotype was relatively stable.
Guoling
Yang
Y
Department of Bioengineering, Dalian University of Technology, 116024, Dalian, China. yanggl@medmail.com.cn
Xiaohong
Yu
Y
Jingrong
Lin
L
Liji
Jin
J
Lijia
An
A
D015139:Blotting, Southern; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D005838:Genotype; D006801:Humans; D010641:Phenotype; D010858:Pigmentation; D016133:Polymerase Chain Reaction; D012337:RNA, Ribosomal, 18S / Q000737:chemistry / Q000235:genetics; D012340:RNA, Ribosomal, 5.8S / Q000737:chemistry / Q000235:genetics; D014005:Tinea / Q000382:microbiology*; D014249:Trichophyton / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*
D004271:DNA, Fungal; D021903:DNA, Ribosomal Spacer; D012337:RNA, Ribosomal, 18S; D012340:RNA, Ribosomal, 5.8S