The group recently published a paper in the journal Cell Systems. In it, researchers explain how a series of sensors, circuits and memory switches could be encoded in the bacterium Bacteroides thetaiotaomicron, commonly found in the human gut.
According to the engineers, their technology could allow bacteria to sense, memorize and respond to signals in the gut. It could potentially be used to detect and treat inflammatory bowel disease, for instance. “We wanted to work with strains like B. thetaiotaomicron that are present in many people in abundant levels and can stably colonize the gut for long periods of time,” said Timothy Lu, an associate professor of biological engineering and of electrical engineering and computer science.
The researcher’s genetic parts can program gene expression within the bacteria. “Using these parts, we built four sensors that can be encoded in the bacterium’s DNA that respond to a signal to switch genes on and off inside B. thetaiotaomicron,” says biological engineering professor Christopher Voigt, adding that these can be food additives such as sugar.
The engineers needed to find a way for the bacteria to remember information (such as bleeding or an inflammation) and report it externally. They did this by providing B. thetaiotaomicron with a genetic memory of sorts; a protein called recombinases that records information into bacterial DNA. The team did not reveal how it obtains the information from the bacteria.
The researchers also relied on CRISPR interface technology to control which genes are turned on and off in the bacterium. They used it to modulate the ability of B. thetaiotaomicron to “consume a specific nutrient and to resist being killed by an antimicrobial molecule.”
During an experiment with mice, the team was able to successfully colonize the gut of the rodents. The bacteria remembered what the mice ate when they were fed specific foods that contained the right ingredients.
The engineers are now hoping to expand the application of their technology beyond B. thetaiotaomicron. “We aim to expand our genetic toolkit to a wide range of bacteria that are important commensal organisms in the human gut,” Lu adds.
For more information about the research, visit MIT’s website.