Runyon group II Mycobacteria are slow-growing and form yellow-orange colonies that do not depend on exposure to light.

• A. True
• B. False
• C. Not applicable
• D. Not enough information

Answer: (A)

Runyon group II Mycobacteria are scotochromogens. Their defining trait is pigment production that occurs in the dark and does not require light exposure, which is why they’re described as pigmenting regardless of lighting. They are slow-growing, taking longer to form colonies, and the pigment is typically yellow to orange. This combination of slow growth and light-independent pigment distinguishes them from photochromogens (which only pigment after light exposure) and nonchromogens (which do not pigment at all). So the statement about slow growth, yellow-orange pigment, and pigment independent of light accurately describes this group.