Which type of fungi is described as facultative anaerobes?

• A. Nonfilamentous (yeast)
• B. Filamentous (mold)
• C. Both
• D. Neither

Answer: (A)

Facultative anaerobes are organisms that can grow with or without oxygen, switching between respiration when oxygen is present and fermentation when it isn’t. Yeasts, which are nonfilamentous and unicellular, commonly ferment sugars into alcohol and CO2 in low-oxygen environments while using aerobic respiration when oxygen is available. This metabolic versatility is why yeasts are described as facultative anaerobes. Filamentous fungi, or molds, rely mainly on aerobic respiration and require oxygen for growth, so they aren’t characterized as facultative anaerobes.