Cells in the body use hormones to communicate, for example controlling the fundamentals of human procreation through estrogen and testosterone. Similarly, bacteria colonies reach certain sizes and then individuals release chemicals to guide its overall development. Now researchers have tapped this cellular communication to create synthetic ecosystems replicating organisms that rely—or feed—on one another to survive, among other activities.
The communication system could be used to produce pharmaceuticals or create synthetic prosthetic networks of cells to replace damaged natural networks in the human body, according to Martin Fussenegger, a biotechnologist at the Swiss Federal Institute of Technology in Zurich. Already, researchers have used it to produce beta interferon, a cell-killing human immune system protein used in the treatment of multiple sclerosis.
"We have used a synthetic biology approach: assembly of functional genetic parts to design replicas of natural phenomena," Fussenegger says. "We were fascinated by the communication between different species—the secret molecular language which orchestrates their coexistence—and, in order to have a basic idea of how such cross talk could work, we designed our synthetic ecosystems."
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Specifically, Fussenegger and his colleagues engineered an airborne communication system—dubbed "AT&T" for airborne transmission of transcription transfer information—that relies on mammalian cells to convert ethanol to acetaldehyde. The latter chemical evaporates at roughly 21 degrees Celsius (70 degrees Fahrenheit) and travels to receiver cells, where it triggers various cellular processes.
The AT&T system can work either for individual cells in culture (in the lab) or function in vivo in actual mice, the researchers report in Proceedings of the National Academy of Sciences USA. "A sender population and a receiver population are implanted at different sites of the mouse and communicate across the body via AT&T," Fussenegger says. "If the mouse receives ethanol, this is converted by the sender population in acetaldehyde, which diffuses through the body to the receiver population and triggers expression of a human glycoprotein, which can be quantified in the [blood] of these animals."
Using this basic signaling technology, the scientists created a variety of functioning ecosystems in lab samples. For example, Escherichia coli bacteria engineered to produce acetaldehyde enabled adjacent mammalian cells to thrive and mammalian cells engineered to produce an apoptosis protein (a signal for cells to kill themselves) wiped out an adjacent E. coli population. Further, by using the antibiotic ampicillin, the researchers were able to create an ecosystem of E. coli and mammalian cells whose populations rose and fell in a way that is "reminiscent of typical population time courses occurring in wildlife parasite-host or predator-prey interactions," the team wrote.