Pamela Peralta-Yahya’s lab at the Georgia Institute of Technology develops technologies to better engineer biological systems for chemical synthesis, and the group is getting front-page treatment on a national scale to showcase its groundbreaking work.

The cover for the December issue of ACS Synthetic Biology features an artistic depiction of the group’s latest research in the development of biosensors to screen chemical-producing microbes, which could lead to the faster, more efficient production of chemicals.

Peralta-Yahya conceived the research, which is entitled “GPCR-Based Chemical Biosensors for Medium-Chain Fatty Acids,” and designed the experiments with her co-authors, post-doctoral researcher Kuntal Mukherjee and former lab member and graduate student Souryadeep Bhattacharyya.

They set out to address one of the key limitations to engineering microbes for chemical production, which is the reliance on low-throughput chromatography. Many value-added chemicals require sensors for high-throughput screening – that’s what Peralta-Yahya and her colleagues are going after.

“We engineer microorganisms to make chemicals and one of our areas is making biofuels,” says Peralta-Yahya, who is an assistant professor in the School of Chemistry and Biochemistry and a faculty researcher with the Petit Institute for Bioengineering and Bioscience. “Right now, when we engineer a biofuel-producing microorganism – when we make changes and screen large numbers of cells to determine how the changes affect the microorganism’s biofuel production – we use chromatography, so we can only test 100 samples a day. It limits what we can do.”

For the larger scale genome engineering Peralta-Yahya has in mind, a process that can screen on the order of 10 million samples a day is needed. 

But making biosensors for biofuel precursors isn’t easy, she says, “because biofuels are hydrocarbons, so they don’t have a lot of functional groups to bind, which is one way of triggering a sensor.”

So they used G-protein coupled receptors (GPCRs, a class of protein at the root of our five senses) as a sensing unit. GPCRs naturally bind a wide array of chemicals, including medium-chain fatty acids, which are immediate precursors to advanced biofuel fatty acid methyl esters (which comprise biodiesel).

“This research was the first to show that we can quickly assemble sensors for these difficult molecules, like biofuels,” says Peralta-Yayha, who actually co-authored not one, but two research papers published in December’s ACS Synthetic Biology.

“To our knowledge this is the first report of a whole-cell medium-chain fatty acid biosensor,” the researchers write, “which we envision could be applied to the evolutionary engineering of fatty acid-producing microbes.” 

To carry out their experiments, the team made use of the Petit Institute’s core facilities, particularly the Cellular Analysis core and its BD LSR II Flow Cytometer. Flow cytometry is a powerful method for isolating cells of interest (and investigating many aspects of cell biology, for that matter). The equipment allowed Peralta-Yahya’s team to run their samples and quickly attain and analyze the data.

Meanwhile, the second article, entitled, “Pterin-Dependent Mono-oxidation for the Microbial Synthesis of a Modified Monoterpene Indole Alkaloid,” touches on another focus area of the Peralta-Yahya lab: pharmaceutical precursors.

Monoterpene Indole Alkaloids (MIAs) have important therapeutic value as anticancer, antimalarial and antiarrhythmic agents. They are derived from plants, but the challenge is, “plants take a long time to grow and they produce very little of the compound you want,” says Peralta-Yahya, who co-authored the article with graduate students Amy Ehrenworth and Stephen Sarria. 

“If you can make a microbe that produces that precursor, then we can produce larger quantities and produce it faster,” Peralta-Yayha says. “So in this research we make a derivatized alkaloid, removing a few steps for the chemist in the process from plant precursor to the final drug.”

The researchers conceived the first microbial synthesis of a modified MIA, with its important medicinal compounds.

“This work opens the door to the scalable production of MIAs as well as the production of modified MIAs to serve as late intermediates in the semi-synthesis of known and novel therapeutics,” the authors write. “Further, the microbial strains in this work can be used as plant pathway discovery tools to elucidate known MIA biosynethetic pathways or to identify pathways leading to novel MIAs.”

CONTACT:

Jerry Grillo
Communications Officer II
Parker H. Petit Institute for
Bioengineering and Bioscience