Arcanobacterium pyogenes was formerly considered a member of which genus?

Arcanobacterium pyogenes was formerly considered a member of which genus?

• A. Corynebacterium
• B. Streptococcus
• C. Listeria
• D. Bacillus

Answer: (A)

Taxonomic classification can change when we gain more detail about an organism’s biology. Arcanobacterium pyogenes was originally grouped with Corynebacterium because both are Gram-positive, rod-shaped, non-spore-forming bacteria that look similar under the microscope and share early staining and cultural characteristics. As more advanced analyses—biochemical tests and, later, genetic comparisons—were done, it became clear that this organism forms a distinct lineage separate from Corynebacterium. To reflect those differences, scientists established a separate genus, Arcanobacterium, for this and related species. So historically it was considered part of Corynebacterium, which is why that option is the correct historical classification.