Which of the following bacteria is used as a vector for plant genetic engineering ?
1) Agrobacterium tumefaciens
2) Bacteriophages
3) Thermus aquaticus
4) Pyrococcus furiosus

Options

A. 1) Agrobacterium tumefaciens
B. 2) Bacteriophages
C. 3) Thermus aquaticus
D. 4) Pyrococcus furiosus

Explanation

To determine which bacteria is used as a vector for plant genetic engineering, we will analyze each of the provided options step by step.

### Step 1: Understand the concept of a vector in genetic engineering
A vector is an organism or a vehicle that carries foreign genetic material into another cell. In the context of plant genetic engineering, vectors are used to introduce new genes into plant cells.

**Hint:** Remember that vectors are crucial for transferring DNA into host organisms.

### Step 2: Analyze the first option - Agrobacterium tumefaciens
Agrobacterium tumefaciens is a well-known bacterium that acts as a vector in plant genetic engineering. It is a plant pathogen that causes crown gall disease by transferring a part of its DNA (T-DNA) into the plant cells, leading to tumor formation. This characteristic is exploited in genetic engineering to introduce new genes into plants.

**Hint:** Look for bacteria that have a natural ability to transfer DNA into plant cells.

### Step 3: Analyze the second option - Bacteriophages
Bacteriophages are viruses that specifically infect bacteria. They are not used in plant genetic engineering because they do not have the capability to infect plant cells. Instead, they serve as vectors for transferring genetic material in bacterial systems.

**Hint:** Consider whether the organism can infect plant cells or not.

### Step 4: Analyze the third option - Thermus aquaticus
Thermus aquaticus is a thermophilic bacterium known for its heat-stable DNA polymerase, which is used in PCR (Polymerase Chain Reaction). However, it does not serve as a vector for plant genetic engineering.

**Hint:** Think about the applications of the organism and whether it relates to plant genetic engineering.

### Step 5: Analyze the fourth option - Pyrococcus furiosus
Pyrococcus furiosus is another thermophilic archaeon that does not act as a pathogen or vector for plants. It is primarily studied for its enzymes but is not used in genetic engineering of plants.

**Hint:** Evaluate if the organism has any role in plant genetic engineering.

### Conclusion
After analyzing all the options, the only bacterium that serves as a vector for plant genetic engineering is **Agrobacterium tumefaciens**. Therefore, the correct answer is:

**Answer: 1) Agrobacterium tumefaciens**