Engineering Made Easy(er)

Penn State engineers develop a “genetic circuit” and streamline a process.

Penn State engineers have developed a new “portable power supply” that will make it easier to manufacture plastics, therapeutics, fuels, and other chemicals from sustainable feedstocks using diverse microbial organisms.

“This will have a huge impact on how organisms are engineered to make many different products,” said Howard Salis, assistant professor of chemical engineering and agricultural and biological engineering.

The team’s engineered system is analogous to the power supply inside all computers that plugs into power sockets and converts fluctuating AC power into a smooth DC current.

Manish Kushwaha, a postdoctoral fellow in agricultural and biological engineering, worked with Salis to build the system. He engineered a genetic circuit that could supply the organism with a portable RNA polymerase, a key enzyme responsible for reading DNA and making RNA that is central to expressing the organism’s genes. But that wasn’t the difficult part.

Kushwaha explained, “The trick was to find a way to make the same amount of RNA polymerase in different organisms without using organism-specific genetic parts. We wanted to find a way to make RNA polymerase inside a cell without relying on the cell’s genetic machinery.”

The solution was to introduce a genetic control system—a positive feedback loop and a negative feedback loop—so that RNA polymerase could be made in any bacterial cell regardless of differences in the cell’s genetic machinery.

Salis and Kushwaha demonstrated how their portable power supply works inside three very different bacterial organisms, showing how the same genetic parts could be used to make a recombinant protein and a 3-enzyme pathway. The results appear in the July 17 issue of Nature Communications.

—Mindy Krause