Cyanide forces bacterial evolution.

What is it about?

Cyanide is regarded as a poison for most living beings but, curiously, this molecule is essential to explain the origin of life in the context of the prebiotic evolution. In this manuscript, we show that cyanide seems to drive bacterial evolution in the contemporary biosphere. The idea that stressing conditions impulses evolution is not new, but here we show a molecular mechanism behind the process: Cyanide triggers iron deprivation that, in a process mediated by the master regulator protein Fur, induce the expression of TonB‐dependent receptors gates that may serve for the entrance of foreign nucleic acids. At the same time, in P. pseudoalcaligenes CECT 5344, cyanide repress the expression of a CRISP‐Cas system. In other words, in the presence of cyanide the bacterium takes a reasonable risk with respect to both the uptake of (TonB-dependent receptors gates) and the tolerance to (reduced immunity) foreign nucleic acids.

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Why is it important?

Horizontal gene transfer (HGT) is the principal driving force in early cellular evolution, but once a certain limit of metabolic fitness is reached, evolution probably becomes conservative (self-replicating), avoiding innovative events though DNA exchange that could be deleterious. In this manuscript we show that cyanide makes this bacterium lower its guard during a discrete time. If the event (HGT) fruitfully succeeds, the stress will disappear and the system will turned back to safe levels. This equilibrium seems to be an example of ‘The Darwinian Threshold’ in the molecular scope.

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