When a bacteriophage infects an E. coli cell, which part of the virus enters the bacterial cytoplasm?

• A. Both the viral nucleic acid and tail fibers
• B. Only the viral protein coat
• C. The entire virus particle, including the capsid
• D. Only the viral nucleic acid

Answer: (D)

Verified step by step guidance

1. Understand the structure of a bacteriophage: it consists of a protein coat (capsid), tail fibers, and nucleic acid (DNA or RNA) inside the capsid.
2. Recall the infection process: when a bacteriophage attaches to an E. coli cell, it uses its tail fibers to recognize and bind to specific receptors on the bacterial surface.
3. Recognize that during infection, the bacteriophage injects its genetic material into the bacterial cytoplasm, but the protein coat and tail fibers remain outside the cell.
4. Therefore, only the viral nucleic acid enters the bacterial cytoplasm, while the rest of the virus stays attached to the cell surface.
5. This mechanism allows the viral genome to take over the bacterial machinery for replication without the entire virus particle entering the cell.