A group of MIT researchers has modified the DNA of bacteria of the species Escherichia coli – or simply E. coli – and used them as memories. A system called SCRIBE (Synthetic Cellular Recorders Integrating Biological Events) allows to easily write and read stably recorded memories, making them suitable for applications such as medical and environmental sensors.
This research was described in an article just published in the journal “Science”. This technique overcomes many limitations of existing methods for recording memories in the DNA of bacteria. Those methods use many elements of genetic regulation that restrict the amount of information that can be recorded.
The biologist Timothy Lu and his colleagues have modified the cells of E. coli so that they would produce a recombinase enzyme that can insert a DNA sequence in a targeted area. This DNA is produced only in the presence of a predetermined molecule or another type of activator such as light.
After the DNA is produced, the recombinase enzyme inserts it into the genome of the cell in the targeted area. Timothy Lu has used the metaphor of a tape recorder because it’s possible to determine where the DNA is inserted into the “tape” of the genome.
When the DNA is written, it will remain recorded during all the life of the bacterial population and passed from generation to generation. It can be read in different ways. If it’s recorded in a non-functional genome, its sequencing will reveal if it’s recorded in a certain cell. The researchers can also use the new DNA to alter a gene.
An example of application of the method of gene alteration tried during this research is the activation of a resistance to antibiotics. This allowed the researchers to determine how many cells received the DNA sequence by exposing bacteria to antibiotics and checking how many of them survived. The resistance of bacteria to antibiotics is a problem that is becoming more and more serious so any technique that allows new research can be very helpful.
The transformed bacteria may be used as biological sensors to be used in many different environments. The E. Coli is a very common also species of bacteria present in the gut of many animal species, including humans. Therefore, using them for example to monitor the diet or possible inflammation in a patient wouldn’t involve the introduction of new species of bacteria. The trials are just starting out but there are really a lot of potential applications, also in the environment.
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