Which of the following statements about Escherichia coli is true?

• A. E. coli is an obligate anaerobe that cannot survive in the presence of oxygen.
• B. E. coli is a Gram-positive bacterium responsible for tuberculosis.
• C. E. coli is a virus that infects bacterial cells.
• D. E. coli is a Gram-negative bacterium commonly found in the human intestine.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the classification of Escherichia coli (E. coli). It is important to know whether it is a bacterium or a virus, and its Gram stain characteristics.
2. Step 2: Recall that E. coli is a bacterium, not a virus. Viruses are acellular and require host cells to replicate, whereas bacteria are cellular organisms.
3. Step 3: Review the oxygen requirements of E. coli. Determine if it is an obligate anaerobe (cannot survive in oxygen) or if it can tolerate oxygen.
4. Step 4: Examine the Gram stain properties of E. coli. Gram-positive bacteria have thick peptidoglycan layers and stain purple, while Gram-negative bacteria have thinner layers and stain pink/red.
5. Step 5: Consider the typical habitat and role of E. coli. It is commonly found in the human intestine and is not responsible for tuberculosis, which is caused by Mycobacterium tuberculosis, a different bacterium.