Since many reactions are thermodynamically more favorable at high temperatures, it has been suggested that hydrothermal environments were the cradle of this “metabolic life.” But Lazcano argued that conversion of this kind of “life” to living organisms required the emergence of a genetic system, raising the problem of nucleic acid stability. Dealing with the latter issue, T. Oshima (Tokyo University of Pharmacy and Life Science) presented data showing that unusual polyamines typical of hyperthermophiles protect both DNA and RNA from denaturation and chemical damage, raising the possibility that these molecules had an essential role in an RNA world.
Another player suggested to have a crucial role in the adaptation of life to very high temperatures, and possibly in the origin of hyperthermophiles, is reverse gyrase, an enzyme inducing positive supercoiling into DNA. P. Forterre (Université Paris-Sud) searched all available genomes for proteins present in all hyperthermophiles and absent in all other organisms. Surprisingly, the only hyperthermophile-specific protein he retrieved is reverse gyrase (8).
