Biologists from the United States have turned the ordinary E. coli into an invulnerable and invisible “super-spy”, teaching it to record information about events occurring around it in its own DNA and save it when handed down to descendants.
“As long as our microbes can simultaneously record three different types of signals over the course of many days, we are now thinking that this way we can observe biomarkers that are present in the body of sick or healthy people,” says Harris Wang, from the University of Columbia in New York (USA).
DNA molecules are a reliable storage device, well protected from reading and writing errors. Scientists are trying to adapt them to store arbitrary data since 1988, when the American bioinformatics first managed to record 7.9 kilobytes of information per DNA molecule and read it.
For example, five years ago biologists from Harvard for the first time “unpacked” the book on DNA molecules and read it using an ordinary sequencer of the genome, and a year ago, scientists from the University of Washington learned to record images in the strands of the genetic code and read them, reaching a record high density of information recording .
All these approaches have one common drawback: they use “bare” DNA molecules that remain stable and “readable” only inside tubes and laboratories. In addition, they are all actually “disposable” – they can be written down and read only once, which makes it impossible to use similar systems of “genetic memory” as a full-fledged replacement for modern information carriers.
Last year, the famous molecular biologist George Church eliminated this problem by adapting the bacterial “antivirus”, the CRISPR / Cas system, to sequentially record information in the DNA of microbes, turning it into a kind of “flash drive”.
Wang and his colleagues took the next logical step – they changed the work of CRISPR / Cas in such a way that this system began to react itself to signals coming from the outside environment and record information about when and how they began to affect the microbe.
To do this, scientists inserted two additional strands of DNA, twisted into a ring, inside the ordinary E. coli. One contained the genome editor himself, and the second contained a special sequence of genetic “letters” -nucleotides, which made this DNA ring copy itself.
According to Wang, CRISPR / Cas was modified in such a way that it began inserting new DNA fragments into the genome of the microbe, not at the appearance of new viruses, but at strictly measured intervals.
In the absence of external signals, a random set of “letters” from the DNA of the E. coli itself enters the “antiviral library” of the bacterium with which the Cas1 protein interacts, and when they appear, a fragment of the second ring containing the gene of the P1 virus. These changes do not disappear from the DNA of the microbe during its division and remain in the genome of its descendants for many generations.
Thanks to this, the E. coli is transformed, as the scientists put it, into a kind of molecular “dictaphone” that continuously records all signals coming from the external environment. In the role of film in this case, the “anti-virus library” CRISPR, and in the role of a microphone – the second ring DNA molecule.
As shown by further experiments, microbes can lead a similar “shadowing” for 8-10 days without serious consequences for themselves and the appearance of incorrigible errors in their DNA. More complex and advanced versions of these “spies” from the microworld, as scientists say, can play the role of medical sensors, detectors of various poisonous or radioactive substances, as well as solve other complex problems.