By Abbas Nazil
Researchers at Northwestern University have uncovered how bacteria control the movement of carbon inside their cells, identifying two versions of a single enzyme that act as metabolic “traffic controllers.”
The study reveals that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) operates as a bifunctional gatekeeper, determining whether carbon from different food sources is used for energy or for building new cellular materials.
By mapping the flow of carbon atoms through bacterial metabolism using isotope labeling, the team showed for the first time that two GAPDH isoenzymes send carbon traffic in opposite directions depending on the type of nutrient consumed.
The findings explain how Pseudomonas putida, a versatile soil bacterium known for breaking down plant waste and plastics, adapts rapidly to different carbon sources by adjusting the balance of these two enzyme forms.
Scientists previously suspected GAPDH played a role in directing carbon flow but lacked direct evidence.
The new research provides that confirmation using advanced metabolomics tools that trace carbon pathways inside living cells.
The study demonstrates that unlike many reversible enzymes that simply respond to available substrates, each GAPDH version in Pseudomonas is specialized for one direction of carbon movement, allowing precise control of metabolic segregation.
This mechanism helps clarify why the bacterium processes sugars and other carbon compounds through distinct metabolic routes, a phenomenon first documented by Aristilde’s group in 2019.
The discovery has significant implications for biotechnology, where engineered bacteria are increasingly used to convert waste materials into valuable chemicals and fuels.
Understanding how these microbial “traffic lights” work could allow engineers to program bacteria to direct carbon toward specific pathways for more efficient chemical production.
Lead researcher Professor Ludmilla Aristilde noted that manipulating these dual enzyme functions may enable the design of microbial systems tailored for recycling complex wastes or producing targeted bioproducts.
