Mycobacterium tuberculosis (Public Health Image Library, NIAID, Image ID: 18139)
A new study shows how bacteria juggle energy needs while digesting complex carbons.
Scientists precisely tracked how ligninderived compounds move through a soil microbe’s metabolism. Lignin is the tough, woody material that gives plants rigidity. The study has implications for harnessing bacteria to upcycle lignin carbons into chemicals of industrial value.
Some bacteria have an ability to digest the seemingly indigestible, including carbon from lignin, the tough, woody material that gives plants their rigidity. A Northwestern University study shows that the Gramnegative rod Pseudomonas putida, a common soil bacterium, completely reorganizes its metabolism to thrive on these complex carbons.
By slowing down some metabolic pathways while accelerating others, the bacterium manages to extract energy from lignin without exhausting itself.
These findings could have implications for the biomanufacturing industry, which has long sought to harness Pseudomonas putida to break down lignin and upcycle it into biofuels, plastics and other useful chemicals. The new information could help researchers build efficient and productive microbial factories.
This is significant since lignin is renewable and sustainable source of carbon that could potentially provide an alternative to petroleum in the production plastics and valuable chemicals. After cellulose, lignin is the second most abundant biopolymer on Earth.
When lignin is broken down, it produces a mix of chemical compounds, including phenolic acids, which could be used as renewable feedstocks for valuable chemicals.
These complex compounds are made up of a ring of six carbons with chains of carbons attached to the ring. Few organisms can process these compounds efficiently. In other words, it simply takes too much energy to digest.
To probe how bacteria strike this balance, the researchers grew P. putida on four common, ligninderived compounds. Next, they used a suite of “multiomics” tools — including proteomics, metabolomics and advanced carbontracing techniques — to map exactly how the bacteria move carbon through their metabolism.
It was shown that, when faced with lignin, the bacterium rewires its metabolism into a highenergy mode. It ramps up the level of enzymes for certain metabolic reactions — sometimes by hundreds to thousandsfold — to reroute digestive pathways, shifting carbon away from the “main highway” to backup metabolic “roads” to avoid bottlenecks. Due to this metabolic remodelling, the bacteria produced six times more ATP — a molecule that provides energy — compared to when it consumes easiertodigest compounds.
This finding could be important for biotechnology applications, where engineers seek to tweak bacteria’s metabolism to produce biobased fuels and chemicals.
The research appears in the journal Communications Biology. The paper is titled: “Quantitative decoding of coupled carbon and energy metabolism in Pseudomonas putida for lignin carbon utilization”.
