The vector used in the first successful recombinant DNA was from :

Options

A. a bacteria that causes pneumonia
B. a bacteria against which the first antibiotic was discovered.
C. a bacteria that can be detected by WIDAL test
D. None of these

Answer

To solve the question regarding the vector used in the first successful recombinant DNA, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding the Concept of Recombinant DNA**:
- Recombinant DNA technology involves combining DNA from different organisms. A vector is a DNA molecule used to carry foreign genetic material into another cell.

2. **Identifying the First Successful Recombinant DNA**:
- The first successful recombinant DNA was created by the company L.E. Lillian.

3. **Determining the Source of the Vector**:
- The vector used in this process was derived from *Salmonella typhi*, which is the bacterium that causes typhoid fever.

4. **Recognizing the Role of E. coli**:
- The vector was designed to be compatible with *Escherichia coli* (E. coli), a common bacterium used in genetic engineering.

5. **Understanding the Application**:
- The recombinant DNA technology developed was significant for creating a test known as the Widal test, which is used to diagnose typhoid fever.

6. **Selecting the Correct Answer**:
- Based on the information, the correct answer to the question is that the vector used in the first successful recombinant DNA was from *Salmonella typhi*.

### Final Answer:
The vector used in the first successful recombinant DNA was from *Salmonella typhi*.