The Dead Sea is not dead, in the science sense. Many microorganisms which inhabit it belong to a group of salt-tolerant archaea (from the Greek archaĩos, from which we also get"archaic“). Archaea are among the most primordial life forms on earth and have managed to survive in extreme environments.
Scientists have long known that salt-tolerant archaea make use of various organic compounds as a source of nourishment in order to synthesize the necessary cell building blocks and vitamins with activated acetic acid, acetyl coenzyme A. Using the microorganism Haloarcula marismortui as a model, Dr. Ivan Berg and other microbiologists at the Institute of Biology II of the University of Freiburg have succeeded in unraveling the details of this metabolic pathway.
In Science, the researchers describe how they were able to shed light on the entire reaction cycle, including all of its intermediate steps, with the help of a variety of biochemical and microbiological methods. The team named the complete metabolic pathway the "methylaspartate cycle" after its characteristic key intermediate.
The researchers also addressed how this new metabolic pathway originated, as the ancestors of salt-tolerant archaea changed their lifestyle in the course of evolution and thus had to 'discover' the metabolic pathway in order to acclimatize themselves to their salty habitat.
The researchers discovered that the genes for this metabolic pathway of the ancestors of salt-tolerant archaea were 'gathered together' from other microorganisms. Lateral gene transfer between organisms is already known but they say scientists had not yet observed a methylaspartate cycle composed entirely of old genes of various functions and completely different metabolic pathways.
The chance (re)combination of all of these genes in an ancestor of salt-tolerant archaea led to this new metabolic pathway. The researchers explain this by stating that it is more difficult and slower to 'invent' new genes than it is to create them by combining existing genes according to the 'evolutionary tinkering' principle.
The concept of 'evolutionary tinkering' is well known in biology but it basically refers to the idea that evolution is not a perfect engineer with planning and a goal, it is more like a 'tinker' which finds improvised solutions to solve pressing problems any way he can. To stay in the metaphor, biological tinkers don't necessarily create new parts (genes) but also use whatever works and is available.
The researchers say this principle is at work in the emergence of new metabolic pathways under extreme conditions.
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