Verified answer

Thermophiles are organisms that grow best above 42°C (body temperature = 37°). A higher G-C content provides DNA with greater thermal stability. (Three hydrogen bonds per base pair are stronger than the two for A-T.)

It is a little unclear what you mean. For example, there are thermophilic bacteria. In general, they have to have many of the same enzymes that bacteria living in normal temperatures do. However, they are probably forms of those enzymes that have higher temperature optima. Their DNA would code for these proteins (most enzymes are proteins) that have these optima, and thus be slightly different from their normal-termperature 'relatives.'