(ORDO NEWS) — Scientists have shown that laboratory experiments very poorly reflect the real evolutionary processes that occur in nature.
Under the influence of simple and strong factors in the experiment, adaptive mutations appear in those regions of proteins that evolve the slowest in nature.
For millennia, humans have unknowingly experimented with evolution by domesticating plants and animals.
At the end of the 19th century, William Dallinger conducted the first laboratory experiments, and since then, scientists have sought to recreate evolutionary processes in artificial conditions as accurately as possible.
Such experiments usually consist of exposing the body to some well-defined factors (toxins, extreme temperatures, nutrient deficiencies) and further studying how organisms adapt to new conditions.
Although such experiments have provided fundamental insights into evolutionary processes such as adaptation, natural selection, and mutation, evolution occurs in nature under much more complex conditions.
Now an international team of scientists has shown how laboratory evolution differs from natural evolution.
Under experimental conditions, adaptations develop in response to simple and strong influences, and often they are provided by mutations that are extremely unlikely in nature.
The scientists examined two genes that code for the RNA polymerase enzyme from the bacterium E. coli.
The authors identified adaptive mutations that change the positions of 140 amino acids in the protein in response to 12 different conditions.
At the same time, there were very few coincidences in the position of the mutations: only four out of 140 developed under more than one experimental condition, while the rest were unique.
Comparing these sites with the rest of the E. coli protein sequences, the scientists found that mutations in the laboratory occurred at highly conserved regions that evolve slowly in the natural environment and remain similar even across species.
In addition, it turned out that mutations obtained in the laboratory tended to fall into certain functional domains of the protein and clustered next to each other.
To see if this is true of other proteins, the researchers examined 19 enzymes containing adaptive mutations associated with resource depletion and antibiotic exposure.
As in the case of RNA polymerase, the sites associated with laboratory mutations were quite conserved. However, the same regularity was not observed when exposed to high temperatures.
Thus, the dynamics of laboratory evolution is very different from the natural one. This is because, in experiments, organisms are subjected to relatively simple, strong, and constant selective pressure.
The action of factors in natural conditions is much more complex, and besides, it changes over time.
Adaptations that occur so easily in experiment are unlikely to occur in nature, and if they do, their frequency can change rapidly as conditions change.
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