Question

The archaeon Sulfolobus acidocaldarius is found in hot acidic springs. Its genome encodes a gene for an ATP-driven topoisomerase that introduces positive supercoils into its circular genome. Why is the presence of this gene so critical to Sulfolobus acidocaldarius?

Answer 1

DNA is a temperature-sensitive molecule and will get denatured if exposed to high temperatures. the positive supercoiling is the form of DNA in which DNA is tightly packed is completely unaccessible. Since these bacteria are living in high temperature they need to pack the DNA tightly in order to prevent the heat-induced denaturation of DNA. If the DNA is negatively supercoiled or more opens there are the chances that it could be denatured by the heat. So in order to maintain the positive supercoiling, so the stability of DNA they use topoisomerase to induce positive supercoiling. If these genes for topoisomerase are absent the bacteria would not be able to pack the DNA tightly and it will remain more relaxed form which will increase the heat induced denaturtaion of DNA leading the death of bacteria.