The plasmid of which organism was used successfully for the first time as vector by Cohen and Boyer

Options

A. Salmonella typhimurium
B. Streptococcus pneumoniae
C. Staphylococcus aureus
D. Rhizobium leguminosarum

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which organism's plasmid was used by Cohen and Boyer as a vector for the first time in recombinant DNA technology.

2. **Identifying Key Contributors**: Recognize that Stanley Cohen and Herbert Boyer were pivotal figures in the development of recombinant DNA technology.

3. **Researching the Plasmid Used**: Cohen and Boyer used a plasmid that contained an antibiotic resistance gene. This is a crucial detail as it indicates the type of plasmid they were working with.

4. **Determining the Source of the Plasmid**: The plasmid used in their experiment was derived from a drug-resistant strain of the bacterium *E. coli*. This bacterium is commonly used in biotechnology due to its well-understood genetics.

5. **Linking to Other Bacteria**: The antibiotic resistance gene was linked to the native plasmid of another bacterium, which is identified as *Salmonella typhimurium*. This is an important connection because it shows the collaborative use of plasmids from different organisms.

6. **Evaluating the Options**: The options provided include:
- *Salmonella typhimurium*
- *Streptococcus pneumoniae*
- *Staphylococcus aureus*
- *Rhizobium leguminosorum*

Based on the information gathered, the correct answer is *Salmonella typhimurium*.

7. **Final Answer**: Therefore, the plasmid of *Salmonella typhimurium* was used successfully for the first time as a vector by Cohen and Boyer.

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