Which of the following is not a source of restriction endonuclease ?
(a) Haemophilus influenzea
(b) Escherichia coil
(c) Entamoeba coil
(d) Bacillus amyloliquifaciens

Options

A. Haemophilus influenzea
B. Escherichia coil
C. Entamoeba coil
D. Bacillus amyloliquifaciens

Answer

To determine which of the following is not a source of restriction endonuclease, we will analyze each option provided:

1. **Haemophilus influenzae**: This bacterium is known to produce a restriction endonuclease called HindIII. Therefore, it is a source of restriction endonuclease.

2. **Escherichia coli**: E. coli is one of the most well-studied bacteria and is known to produce a restriction endonuclease called EcoRI. Thus, it is also a source of restriction endonuclease.

3. **Entamoeba coli**: This organism is a commensal protozoan found in the human gastrointestinal tract. Unlike the previous two, Entamoeba coli does not produce restriction endonucleases. Therefore, it is not a source of restriction endonuclease.

4. **Bacillus amyloliquefaciens**: This bacterium produces a restriction endonuclease known as BamHI. Hence, it is a source of restriction endonuclease.

Based on the analysis above, the correct answer is **(c) Entamoeba coli**, as it is not a source of restriction endonuclease.

### Summary of Steps:
1. Identify the restriction endonucleases produced by each organism.
2. Confirm which organisms are known sources of restriction endonucleases.
3. Identify the organism that does not produce any restriction endonucleases.