Enzyme 'Taq polymerase' used in PCR, has been isolated from bacterium
1) Agrobacterium tumefaciens
2)Thermus aquaticus
3) Streptomyces albus
4) Escherichia coil

Options

A. 1) Agrobacterium tumefaciens
B. 2)Thermus aquaticus
C. 3) Streptomyces albus
D. 4) Escherichia coil

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the source of the enzyme Taq polymerase, which is used in the Polymerase Chain Reaction (PCR).

2. **Identifying Taq Polymerase**: Taq polymerase is a specific type of DNA polymerase that is known for its ability to withstand high temperatures, making it ideal for PCR processes that involve repeated heating and cooling cycles.

3. **Researching the Source**: Taq polymerase is derived from a thermophilic bacterium. The name of this bacterium is crucial to answering the question correctly.

4. **Evaluating the Options**:
- **Option 1: Agrobacterium tumefaciens** - This bacterium is known for causing crown gall disease in plants and is not the source of Taq polymerase.
- **Option 2: Thermus aquaticus** - This is a thermophilic bacterium from which Taq polymerase is isolated. This option is likely correct.
- **Option 3: Streptomyces albus** - While this is a bacterium, it is not the source of Taq polymerase.
- **Option 4: Escherichia coli** - This bacterium is commonly found in the human gut and is not related to Taq polymerase.

5. **Conclusion**: After evaluating all the options, the correct answer is **Option 2: Thermus aquaticus**.

### Final Answer:
The enzyme 'Taq polymerase' used in PCR has been isolated from the bacterium **Thermus aquaticus**.

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