Would Chlamydomonas nivalis have higher/lower GC content than E.coli?Why?

Question

Chlamydomonas nivalis is a species of algae that thrives in freezing water and snow. Would you expect the genome of C. nivalis to have a higher, lower, or similar G-C content as that of E. coli bacteria?

I think its lower because it lives in a lower temperature but not sure if that's correct.

Answer 1

Hi Rahel,

I agree with you that we would expect Chlamydomonas nivalis to have a lower GC content that E. coli. Since Chlamydomonas nivalis is able to survive at lower temperatures, it would be beneficial to have adaptations that make that survival easier. Remember that between each GC interaction there are three hydrogen bonds compared to the two in AT. If a bacterial genome had less GC bonds this means it would have a lower “melting temperature” or the temperature at which the two strands of DNA would separate. You can see how this would be beneficial at the low temperature that Chlamydomonas nivalis lives in. In contrast, E. coli lives at a higher temperature and does not have selective pressure to reduce its GC content. I hope that answers your question. Let me know if you have any more questions.