Influence of the cultivation medium and pH on the pigmentation of Trichophyton rubrum

Area of Science:

• Medical Mycology
• Dermatophyte Research
• Fungal Pigmentation Studies

Background:

• Trichophyton rubrum is a common human pathogenic dermatophyte.
• It causes superficial fungal infections like athlete's foot, nail infections, jock itch, and ringworm.
• The pigmentation of T. rubrum colonies is variable, ranging from white/yellow to red.

Purpose of the Study:

• To investigate the influence of pH on T. rubrum pigmentation.
• To identify the chemical basis for T. rubrum's color variation.
• To explain differential pigmentation on various culture media.

Main Methods:

• Controlled pH experiments using alkaline and acidic conditions.
• Colorimetric analysis of T. rubrum colonies.
• pH monitoring of liquid culture media (Trichophyton medium and Synthetic-Complete medium) over four weeks.

Main Results:

• T. rubrum exhibits red pigmentation under alkaline conditions and yellow under acidic conditions.
• The pigment Xanthomegnin is proposed as responsible for both yellow and red colors.
• Trichophyton medium maintained alkaline pH, resulting in red colonies, while Synthetic-Complete medium acidified, producing yellow colonies.

Conclusions:

• pH is a critical factor determining T. rubrum pigmentation.
• The chemical environment of culture media significantly impacts fungal color.
• Understanding pH-mediated pigmentation is crucial for accurate dermatophyte identification and research.