I added only two "bricks" - and the whole building collapsed …
Two years ago, US scientists announced that they had succeeded in introducing two artificial "letters" of DNA (base pairs) into the genome of a living organism. The researchers planned to test whether it is possible to introduce foreign elements into the genome, how stable the life of such a semi-synthetic bacterium Escherichia coli will be, and whether it will reproduce itself with such "add-ons". But the resulting generations of semi-synthetic microorganisms have demonstrated an unexpected result that made scientists wonder whether they are choosing the right path …
The ultimate goal of all experiments of this kind is the creation of "factories" for the production of substances needed by scientists, for example, new proteins needed by a wide variety of industries.
New research has shown that working with a semi-synthetic organism (at least in this particular modification), most likely, will not work. E. coli E. coli with artificial "letters" in the DNA showed phototoxicity. Simply put, bacteria die when exposed to light. A very small dose of sun exposure or light from fluorescent lamps significantly reduces cell survival and growth.
As it turned out, the fact is that the inserted artificial base pair consists of two nucleosides (nucleotides without phosphate groups), called d5SICS and dNaM. The latter differ in their chemical structure from natural ones, which means that they absorb light of a different wavelength (the difference is not too large - 400 nanometers instead of 300 nm for natural ones).
But the daily doses of radiation (the light of the Sun reaching the Earth's surface and the light of fluorescent lamps) that we and the microorganisms living in the laboratory receive contain much more light with a wavelength of 400 nm (near visible range) than with a wavelength of 300 nm (closer to ultraviolet).
To understand how this difference affects living cells, scientists conducted an experiment. They exposed skin cancer cells to light. It turned out that when exposed to light with a wavelength of 400 nm, even in small doses, the survival rate of ordinary cells without artificial nucleosides did not change. The same was the case with altered cells that were not treated with light.
But cancer cells with "extra letters" in the DNA, which received even a small dose of radiation, showed a significant decrease in proliferation. That is, artificial base pairs made these cells sensitive to the effects of light of a certain wavelength. In fact, they received photochemical damage. Incompatible, as they say, with life …
Promotional video:
Thus, the study showed that even small changes in the genetic code can lead to unforeseen and far-reaching consequences for the whole organism.
However, in this case there would be no happiness, but misfortune helped. The discovery can also serve a good service to humans, as scientists, using the phenomenon of phototoxicity, can come up with a new way to treat cancer.
