A team of scientists from Princeton University has demonstrated a way to precisely control the response of genetically engineered bacteria by switching lights on and off, controlling the bacteria's chemical production.
In a study published in the journal Nature Chemical Biology on September 7, researchers developed a system to control a key genetic circuit in Escherichia coli (E. coli) bacteria to turn them into chemical factories producing compounds like isobutanol, a biofuel material.
A lab technician holds a bacteria culture that shows a positive infection of enterohemorrhagic E. coli
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Engineering Metabolism in Bacteria
"All you need is illumination," said senior author José Avalos, assistant professor of chemical and biological engineering at Princeton University, as well as at the Andlinger Center for Energy and the Environment. He added that the findings have a lot of potential benefits, including the ability to "easily tune and reverse the induction signal."
The new study is built upon a previous study from Avalos and his colleagues back in 2018. In their previous work, they engineered yeast to produce chemicals based on the absence or presence of light. According to the press release from Princeton, E. coli finds a wider usage among scientists and engineers as compared to yeast. Furthermore, while they were not the first to use E. coli and engineer its gene expression in response to light, they were the first to employ light in controlling the chemical production of the bacteria.
Also, the study claims to be the first to use light in controlling the lac operon - a group of genres having a single promoter (a single mRNA) - that allow bacteria to use substances as an energy source through chemical induction.
Avalos explained that the lac operon is the "gold standard circuit" used in decades. "It's not an understatement to say that harnessing the lac operon is one of those key achievements that enabled the explosion in biotechnology," he added.
An Inductive Process in E. coli
In engineering the lac operon to make the E. coli produce a certain chemical, scientists generally make the process inductive - triggering the process only as needed instead of keeping it activated all the time. It allows scientists to control the response of the bacteria by simply switching the light on or off.
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In a demonstration detailed in the study, the researchers covered a section of the petri dish with a tiger stencil, creating a fluorescent print of the same design at the selectively activated sections of the bacteria.
"Again, that's something you couldn't easily do with a chemical because you wouldn't be able to control the diffusion of the chemical as easily," Avalos commented. Also, light is a much cheaper alternative compared to chemical agents. Aside from the costs, a natural trigger most probably leaves less carbon footprint.
E. coli is widely used for the industrial production of goods and specialty materials including a range of plastics and fibers, as well as scents and pigments. Also, as noted in the study, this particular bacteria is also often used to understand the mechanism behind biological processes such as metabolism.
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