Ch 11 Lesson 2 Identifying Fungi & Actinomycetes

Identifying Fungi

• Macroscopic methods involve growing fungi on Potato Dextrose Agar (PDA) plates, which support most fungi growth.
• Different agar types can also aid in identifying specific fungi species.

Identifying Yeast

• Yeasts are analyzed by determining their ability to use nitrogen or carbon as their sole food source.
• The Dye Pour-Plate Auxanogram (DPPA) technique involves adding nitrogen and carbon with agar and a pH dye indicator; color change indicates growth.
• Slanted agar tubes provide increased growth area for better observation.

Identifying Mold

• Macroscopic characteristics include color, growth rate, and colony shape.
• Molds are typically cultured on Sabouraud's glucose peptone agar, ensuring consistent growth rates from the same agar supplier.

Identifying Dimorphic Fungi

• Dimorphic fungi exhibit both mold and yeast phases; identification often involves inducing the yeast phase.
• Three main dimorphic fungi:
  • Histoplasma capsulatum: White or tan, fuzzy, takes weeks to mature.
  • Blastomyces dermatitidis: Starts as white and fuzzy, turns yellow as it ages.
  • Coccidioides immitis: Smooth, large tan colonies.

Identifying Dermatophytes

• Dermatophytes grow on Sabouraud's glucose peptone agar with added antifungal and antibacterial agents to limit other growth.
• Prefer protein as a food source, leading to an alkaline pH, which alters the color of the agar.
• Typically appear white, light-yellow, or tan with a cottony or powdery texture.

Identifying Actinomycetes

• Actinomycetes are bacteria resembling fungi, forming filaments and spores.
• They produce leathery or smooth colonies, which can appear white or as small creamy-colored pinpoint colonies.
• Grown in seawater agar for optimal cultivation.

This quiz focuses on the macroscopic methods used to identify various types of fungi, including yeasts, molds, and actinomycetes. You will learn about growth patterns on PDA plates and the characteristics that differentiate these organisms. Test your knowledge of identification techniques and the diversity of fungi.