Which of the following serve as bacterial defenses against infection by viruses?

• A. Capsid proteins
• B. Restriction enzymes
• C. Ribosomes
• D. Reverse transcriptase

Answer: (B)

Verified step by step guidance

1. Understand the context: Bacteria can be infected by viruses, known as bacteriophages. To protect themselves, bacteria have developed defense mechanisms.
2. Identify the function of restriction enzymes: Restriction enzymes are proteins that cut DNA at specific sequences. They serve as a defense mechanism by cutting up the viral DNA, preventing the virus from hijacking the bacterial cell machinery.
3. Differentiate between the options: Capsid proteins are part of the virus structure, not a bacterial defense. Ribosomes are involved in protein synthesis, not defense. Reverse transcriptase is an enzyme used by some viruses to replicate their RNA into DNA, not a bacterial defense.
4. Focus on the correct option: Restriction enzymes are the correct answer because they specifically target and degrade foreign DNA, such as that from invading viruses.
5. Summarize the bacterial defense mechanism: Bacteria use restriction enzymes to recognize and cut foreign DNA, providing a defense against viral infections by preventing the replication of viral genetic material.