The bacterium turning plant waste into power

Original story from Northwestern University (IL, USA). New study shows how bacteria juggle energy needs while digesting complex carbons. For years, scientists have marveled at bacteria’s ability to digest the seemingly indigestible, including carbon from lignin, the tough, woody material that gives plants their rigidity. Now, a new Northwestern University (IL, USA) study shows that 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. The 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. The study marks the first quantitative blueprint of how bacteria coordinate carbon metabolism and energy production during digestion of lignin carbons. “Lignin is an abundant, renewable and sustainable source of carbon that could potentially provide an alternative to petroleum in the production of plastics and valuable chemicals,” explained Ludmilla Aristilde, who led the study. “Certain microbes naturally have an ability to make precursors to valuable chemicals that are lignin-based rather than petroleum-based. But if we want to take advantage of that natural ability to develop new biological platforms, we first need to know how it works. Now, we finally have a roadmap.” Notoriously tough to digest After cellulose, lignin is the second most abundant biopolymer on Earth. When broken down, it produces a mix of chemical compounds, including phenolic acids, which could be used as renewable feedstocks for valuable chemicals. But scientists have struggled to understand how bacteria manage to feed on these complex compounds. These 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. “Before we eat food, we have to shop for it, cook it and eventually chew it up,” Aristilde commented. “That whole process uses energy but consuming the food also gives us energy. There is a balance between the energy we exert to make the food versus the energy we derive from the food. It’s the same for soil microbes.” SNAP to attention: the protein discerning sour flavor Researchers have revealed a lynchpin of the mechanism behind sour taste.