Bacteria, nucleotide content, and cold temperature?

I was given the following info:


Bacterial Species 1 2


Tm(C) 65 88


Adenine content 41 16


Cytosine content 59 84








I had to come up with the cytosine content by myself (I think it's correct) but the following question has me stumped:





"Explain which bacterial species would be able to survive at temperatures lower than 15C"

Bacteria, nucleotide content, and cold temperature?
What the teacher is asking here is for you to apply the principle of melting temperature. As you should know, G:C pair bond through 3 hydrogen bonds, whereas A:T pair bond through 2 hydrogen bonds. So, it takes more energy to break a G:C bond than an A:T bond. You can see that in your data above; when the Adenosine content is higher, the melting temperature is lower. The inverse is true for the Cytosine content.





Now, to the question. The DNA must be melted by the bacterium when it replicates its DNA. The warmer the temperature, the easier this would be to accomplish. As the helicase zips down the double stranded DNA melting it into two single strands, energy is required. The higher the G:C content, the more energy this requires. So, a species that has a higher A:T content would be able to survive at colder temperatures.
Reply:Listeria monocytogenes can grow at a temp lower than 15 C. It can actually grow at temps as low as 4 C, and will grow on lunch meat even in a fridge!
Reply:Also remember that the amount of A=T, and C=G.


;)