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Scientists Turn Bacteria into Genomic Tape Recorders that Store Cells’ Memories


Image credit: Christine Daniloff/MIT

By the means of randomly sequencing its DNA, researchers succeeded in converting the widely seen gut bacterium E. coli into smallest tape recorder in the world. The latest designed microbes were intently engineered so as to document and store memories from their surroundings that could be traced back later. Such concept was targeted on the living data storage devices, which could be quite useful in acting as tiny environmental sensors or health monitors.

Previously researchers had tried store useful information in bacterial DNA. However, they could only be able to succeed in recording all-or-nothing memories, like something related to whether a certain stimulus was present in the environment or not. Such digital memories therefore failed to provide us with information about how long the exposure was, or how much of the stimulus was present, i.e. analog information, but the new cells could do it instead.

As for creation of the living memory recorders, researchers with the Massachusetts Institute of Technology (MIT) resorted to sequencing DNA discovered in special species of bacteria also known as retrons. Retrons would be capable of having the genetic information for generating enzymes (biological catalysts), which could then produce the single strands of DNA being inserted into the bacterium’s genome. Generally speaking, such strands should be applied by the bacteria in manipulation of their host.

By randomly sequencing DNA, the scientists had succeeded in making retrons that could generate unique DNA sequences when a certain stimulus, like a chemical or a light or, was present. Such strands, acting as an efficient record of the experience, would be then inserted into a particular target site within the genome.

As Timothy Lu, the team leader, said, they could target it anywhere in the genome, which was the reason why they regarded it as a tape recorder, since it was possible to direct it where that signal was written.

As the sequence could be passed on from generation to generation, the memory would be accumulated in a gradual way and was stored for the lifetime of the population. By application of sequencing the genome of the organism, researchers would be then able to recover this stored information. Therefore, by identifying the number of the cells within the population contained the new DNA sequence; scientists would be able to work out the magnitude and duration of the signal. With the greater exposure, they would get the higher proportion containing the sequence.

The ultimate goal that scientists were intended to achieve was to apply this system to monitor the different environments. When researchers were capable of designing the cells responsible for various different stimuli, the potential applications could be quite huge, for instance, they could place such organisms in the ocean for measurement of levels of CO2 or pollution. Another alternative choice was its application in medicine to monitor disease progression, like the spread of cancers, through collecting stimuli being released by diseased cells.

Source: MITScienceSciencemag and New Scientist

Journal reference: Farzadfard, Fahim, and Timothy K. Lu. “Genomically encoded analog memory with precise in vivo DNA writing in living cell populations.” Science 346.6211 (2014): 1256272.