Optogenetics instead of chemicals

Switching on and off the light allows you to control genetically engineered bacteria

Alina Khmeleva, Computerra

Researchers from Princeton University (USA) have created a new and improved method for more precise control of genetically engineered bacteria: simply turning on and off the light. Researchers have developed a system to control one of the key genetic chains needed to turn bacteria into chemical factories that produce valuable compounds (for example, isobutanol for biofuels).

The method uses light to turn off the metabolism of E.coli bacteria. It is this mechanism that is the key to making bacteria produce valuable chemicals. A genetic tool called OptoLac was demonstrated by projecting light onto a bacterial culture. Only bacteria that were not exposed to light produced green fluorescent protein.

"All you need is lighting," said Jose Avalos, associate professor of chemical and biological engineering, and the main author of the study. "The method has many potential advantages, one of which is the ability to easily adjust and reverse the induction signal."

The scientist and his colleagues are not the first to produce E. coli, whose genes are controlled by light. But they were the first to use light to control the production of chemicals. They were also the first to use light to control the lactose operon, a group of genes most commonly used for chemical induction in E.coli.

Usually, researchers rely on the addition of a chemical to trigger the manifestation of a genetically modified trait. But this method has serious limitations. You can't just remove a chemical, so scientists need to wait and see if the dose was calculated correctly.

Instead of relying on a chemical inducer, the researchers created bacteria using the absence of light to trigger reactions that lead to chemical formation or protein production. This allows researchers to slow down or stop the reaction by simply turning on the light. The light also allows you to control where the reaction takes place.

In one experiment, scientists demonstrated this process. They darkened only certain areas of the Petri dish using a tiger stencil, creating a fluorescent print as a result of the reaction of selectively activated bacteria.

OptoLac, the team's new optogenetic – or light–based -method, now gives scientists the opportunity to use the already existing lactose operon technology with additional precision and control. Light, unlike chemicals, is relatively inexpensive, so its use will reduce costs and, possibly, carbon waste from chemical processes.

E. coli is currently used for the industrial production of a wide range of commercial and specialty chemicals, from building blocks made of plastic and synthetic fibers to high-quality chemicals such as pigments and flavors.

Also, bacteria are often used by scientists to better understand the basic principles of metabolism, biosynthesis and other processes. The new technology can be of great importance not only for the field of biotechnology, but also for other fundamental research.

The study was published in the journal Nature Chemical Biology (Lalwani et al., Optogenetic control of the lac operon for bacterial chemical and protein production).

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