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How Bioengineered Bacteria Could Give Robots a Living Brain

Researchers are applying mathematical models in a virtual environment to test out a bacteria-powered cyborg prototype.
Warren Ruder, assistant professor in biological systems engineering at Virginia Tech in his lab. Image: Virginia Tech

Imagine a future where robots with organic brains could be controlled through their microbiome. That might become reality, if researchers at Virginia Tech can transfer their virtual simulations of a bacteria-powered robot into the real world.

In a study published today in Scientific Reports, Keith C. Heyde and Warren Ruder, who both hail from the Department of Biological Systems Engineering at Virginia Tech in the US, describes using a mathematical model to demonstrate how a microbiome of engineered bacteria (E. coli) could be used to control a robot. To do this, Ruder mashed together an E. coli microbiome, a microfluidic chemostat that measures the reactions of the bacteria inside them with sensors, and simple mobile robots—all in a virtual simulation.

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"We think of the robot as if it were a host organism, and we think of the bacteria like the microbiome that lives on that host," Ruder told me over Skype. "To build this model, we created a set of mathematical equations and relationships between the components of such a system, which we simulated on a computer. This was to see what kind of behaviours emerged from a combined system."

Ruder explained that cells in a microfluidic chemostat could be engineered to emit, for example, a fluorescent light or protein. These signals, he said, could be picked up by a microscopes fitted onto the microfluidic chemostat, then fed into the robot, making it move in certain directions.

Warren Ruder used a mathematical model that showed an engineered bacteria controlling a robot. Image: Virginia Tech

When the researchers tested out their bot's behaviour in their virtual sim, they found that more interesting behavioural patterns emerged when the robot was able to give signals back to the bacteria it was receiving commands from.

"We thought a more complex behaviour emerged where the robot started to have a somewhat predatory response to different types of food sources in its environment. It would pause briefly as the protein levels from the output of the genetic circuits [on the bacteria] changed, then it would move rapidly toward the food source," explained Ruder. "This is kind of like when a lion is stalking a gazelle and where you see it slowly approach then pounce."

According to Ruder, the take home message of all this is that complex behaviours can emerge through a simple set of relationships defined by mathematical models.

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Synthetic biology has been growing exponentially as a field over the last decade, with the global synthetic biology market estimated to reach $10.8 billion by 2016. Ruder envisions that, in the future, bacteria-robot systems could be used to investigate the interactions between soil bacteria and livestock. He also thinks engineered bacteria could be deployed to help clean up oil spills. That said, Ruder acknowledged that controlling bioengineered organisms in a wild environment is one of the core challenges of of synthetic biology.

"People talk about introducing genetically engineered bacteria to the environment—they could sense things in the environment, maybe find a pollutant and chemically process it so it was less toxic," said Ruder. "But it could be a real challenge to get the bacteria back out of the environment once the job is done."

Ruder envisions that the robot could act as a containment device or a mobile protective shell for the bacteria on board.

"[Say] we engineer those types of bacteria with unique abilities and we give them a robotic platform or a life support system so that they can go out into that environment," said Ruder. "When the bacteria have done their job in the environment because they're housed on a robotic life support, we can simply pull the plug on the life support, the bacteria die and we have no worry that they're going to invade the environment."

Currently, there is only one robot, one bacteria, and one chemostat in the researchers' virtual sim. But next up, Ruder said he wanted to create a virtual environment with multiple robots competing with one another to transfer their microbiome in a survival of the fittest type scenario.

"If you add multiple robots to that same virtual arena, they will run into one another, and just like in nature where the fittest survive, the fast-moving robot will effectively transfer its microbiome onto another robot," said Ruder. "This potential mating behaviour will lead to more complex robot behaviours emerging."