What is the predominant indigenous biota of the colon?

What is the predominant indigenous biota of the colon?

• A. Anaerobic, gram-negative, nonspore-forming bacteria
• B. Anaerobic, gram-positive, nonspore-forming bacteria
• C. Aerobic, gram-negative, nonspore-forming bacteria
• D. Aerobic, gram-positive, spore-forming bacteria

Answer: (A)

The colon is a highly anaerobic environment, so its resident microbes are predominantly anaerobes. Among these, the most abundant group are gram-negative, nonspore-forming anaerobes such as Bacteroides, which are well adapted to fermenting complex carbohydrates in the gut. This combination—anaerobic lifestyle with gram-negative, nonspore-forming characteristics—best describes the major indigenous biota of the colon. While there are anaerobic gram-positive organisms and some spore-formers in the colon, they are not the dominant residents, and aerobic bacteria are less common in this low-oxygen habitat.

The colon is a highly anaerobic environment, so its resident microbes are predominantly anaerobes. Among these, the most abundant group are gram-negative, nonspore-forming anaerobes such as Bacteroides, which are well adapted to fermenting complex carbohydrates in the gut. This combination—anaerobic lifestyle with gram-negative, nonspore-forming characteristics—best describes the major indigenous biota of the colon. While there are anaerobic gram-positive organisms and some spore-formers in the colon, they are not the dominant residents, and aerobic bacteria are less common in this low-oxygen habitat.