Question

Bacteria use DNA methylation as a method to label their DNA, so they can identify foreign DNA and degrade it using restriction endonucleases. This DNA methylation is different than that of eukaryotic organisms, in that it adds a methyl group to adenine. This makes the bacterial DNA methylation system a potential antibiotic target.

Question 1: (3 marks) Based on what we learned about enzyme activity and regulation, explain what you would expect for the following enzymes:

How would this differ for taqDamI isolated from the hot springs bacteria, Thermus aquaticus, which thrives at 70 °C, but can survive at temperatures of 50°C to 80°C?

Consider enzyme activity for taqDamI isolated from the hot springs bacteria, Thermus aquaticus, which thrives at 70 °C, but can survive at temperatures of 50°C to 80°C at the following temperatures: 4⁰C, 22⁰C, 37⁰C, 55⁰C, and 70⁰C. How would this differ for pcrDam, the methyltransferase produced by Psychrobacter cryohalolentis, a bacteria species that grows in temperatures from -10 to 42 °C, and thrives at 4°C?

A. List the expected activity level of each enzyme at the temperatures listed in the table below. (none, low, moderate, high) (2 marks)

Temperature	Thermus aquaticus taqDamI	P. cryohalolentis pcrDam
4⁰C
22⁰C
37⁰C
55⁰C
70⁰C

B. Why is temperature important to enzyme activity? (1 mark)

Answer 1