A DNA "tape recorder" is now able to record activities of human cells, as well as the conditions affecting the structure. Strands of genetic code, designed to be read by researchers, are able to record changes within a cell over the course of several weeks.
Common E. coli bacteria were modified to store information for far longer periods of time than occurs in nature.
Cells send signals from one to another, and back again, communicating information about their chemical makeup and recent activity. As the tiny bodies pass one another, chemicals within cells alter slightly, and messages are passed between the structures.
Biologists previously developed cells that will switch the production of certain proteins on and off in response to external stimuli. These structures came with several disadvantages for human cell research. First, only a single question cold be answered at once. For instance, whether the cell had been exposed to a certain stimulus. However, this early technology was unable to record how long it had been exposed, or to what degree. The information would also be lost if the cell died before being read by biologists.
"We wanted a system that would be easier to scale up to collect more than one piece of information. So we started out, as engineers, thinking about what an ideal memory system would look like," Timothy Lu, a synthetic biologist at Massachusetts Institute of Technology (MIT) said.
The DNA code within E. coli cells were modified to record data about the influence of chemicals and electromagnetic interactions in such a manner that the changes would still be in place, even following cellular death. Populations of the modified cells could be studied, in order to determine the duration and extent of exposure. Severity of exposure, for instance, could be determined by the percentage of cells that exhibit code marking an encounter with the stimulus.
"Rather than treating each individual cell as a digital storage device, Farzadfard and Lu treat an entire population of cells as an analog 'hard drive,' greatly increasing the total amount of information that can be stored and retrieved," Shawn Douglas of the University of California at San Diego, a scientist not involved in the study, said.
Retrons naturally produce single strands of DNA that are used to infect hosts of bacteria like E. coli. Researchers placed specific retrons within the bacteria, which respond to particular wavelengths of light or chemicals. During DNA reproduction, the custom segments of genetic code replace the natural components in response to external stimulus, providing a record of the event.
Synthetic Cellular Recorders Integrating Biological Events (SCRIBE) could be used to record contaminants in water for environmental monitoring. They could also be ingested by patients to monitor dietary intake.
Development of the DNA tape recorders was profiled in the journal Science.
