From which organism was the first restriction enzyme isolated?

Options

A. Escherichia coli
B. Salmonella typhimurium
C. Bacillus cereus
D. Staphylococcus aureus

Explanation

**Step-by-Step Solution:**

1. **Understanding Restriction Enzymes**: Begin by recognizing what restriction enzymes are. They are proteins that cut DNA at specific sequences, and they are crucial tools in biotechnology.

2. **Identifying the First Restriction Enzyme**: The question asks specifically about the first restriction enzyme that was isolated.

3. **Researching Historical Context**: The first restriction enzyme was discovered in the early 1960s.

4. **Identifying the Organism**: The organism from which this first restriction enzyme was isolated is *Escherichia coli* (commonly known as E. coli).

5. **Citing the Researcher**: The enzyme was isolated by Hamilton O. Smith in 1963.

6. **Confirming the Answer**: Based on the information gathered, the first restriction enzyme was indeed isolated from *E. coli*.

**Final Answer**: The first restriction enzyme was isolated from *Escherichia coli* (E. coli).

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