Plasmid used to construct the first recombinant DNA was isolated from which bacterium species?

Options

A. Escherichia coli
B. Salmonella typhimurium
C. Agrobacterium tumefacines
D. Thermus aquaicus

Explanation

To answer the question regarding the bacterium species from which the plasmid used to construct the first recombinant DNA was isolated, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the specific bacterium species from which the plasmid used in the first recombinant DNA technology was derived.

2. **Historical Context**: The first recombinant DNA was constructed in 1972 by scientists Stanley Cohen and Herbert Boyer. Recognizing the contributors to this scientific milestone is crucial.

3. **Identifying the Plasmid Source**: The plasmid used in this groundbreaking experiment carried an antibiotic resistance gene. It is important to identify which bacterium species provided this plasmid.

4. **Evaluating Options**: The options provided are:
- A. Escherichia coli
- B. Salmonella typhimurium
- C. Agrobacterium tumefaciens
- D. Thermus aquaticus

5. **Correct Answer**: The plasmid used to construct the first recombinant DNA was isolated from **Salmonella typhimurium**. Thus, the correct option is **B**.

### Final Answer:
The plasmid used to construct the first recombinant DNA was isolated from **Salmonella typhimurium**.

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