Nutrient pollution, caused by excess nitrogen and phosphorus in water or air, is the number-one threat to water quality worldwide and can cause algal blooms, a toxic soup of blue-green algae that can be harmful to people and wildlife. Every time it rains, fertilizers, pesticides, and animal waste from farms and livestock operations wash nutrients and pathogens-such bacteria and viruses-into our waterways. It’s also a major contributor of contamination to estuaries and groundwater. In the United States, agricultural pollution is the top source of contamination in rivers and streams, the second-biggest source in wetlands, and the third main source in lakes. Around the world, agriculture is the leading cause of water degradation. “There are probably lots of other worm species out there that can degrade plastics,” he said.Not only is the agricultural sector the biggest consumer of global freshwater resources, with farming and livestock production using about 70 percent of the earth’s surface water supplies, but it’s also a serious water polluter. A 2016 study identified the enzymes in a species of bacteria that could break down a type of plastic called poly(ethylene terephthalate). In 2014, Wu and colleagues at Stanford University found that a gut bacterium in another species of wax worm could break down polyethylene, although it had different byproducts. “Plastic pollution is a big global problem,” Bornscheuer said. Scientists have searched for a way to biodegrade plastics for decades, says Uwe Bornscheuer, a biochemist at the University of Greifswald in Germany. Bertocchini hopes to identify the precise enzymes that break down polyethylene in future work. That enzyme converted polyethylene into ethylene glycol, a chemical commonly used in antifreeze. This told Bertocchini and colleagues that an enzyme in the worms or the bacteria living in and on their bodies was dissolving the plastic.
Sure enough, they found the liquid larvae could also eat holes in plastic. To rule out munching action from their jaws as the source of degradation, the team applied a soupy blend of recently deceased worms to the plastic and waited. At this rate, it would take these same 100 worms nearly a month to completely break down an average, 5.5 gram plastic bag. Overnight, 100 wax worms degraded 92 milligrams of a plastic shopping bag. When they placed the worms on polyethylene plastic, they found that each worm created an average of 2.2 holes per hour. Solving the Mysteryīertocchini teamed up with fellow scientists Paolo Bombelli and Christopher Howe to figure out how the wax worms were pigging out on plastic. “Since they eat wax, they may have evolved a molecule to break it down, and that molecule might also work on plastic,” Bertocchini said.
Both wax and the polyethylene in Bertocchini’s plastic bag had a similar carbon backbone. Like plastic, wax is a polymer, which consists of a long string of carbon atoms held together, with other atoms branching off the sides of the chain. The larval form of a small moth, wax worms get their names because they live on the wax in bee hives. Although Bertocchini wasn’t an entomologist, she guessed immediately what was happening. When she checked the bag an hour later, however, she discovered small holes in the part of the bag with the larvae.
She removed some wax worms ( Galleria mellonella) living in the hive and placed them in an old plastic bag. She first noticed the possibility as she cleaned out her backyard bee hives two years ago. The discovery was led by Federica Bertocchini, a developmental biologist at the University of Cantabria in Spain. “This study is another milestone discovery for the research on biodegradation of plastics,” says Wei-Min Wu, an environmental engineer at Stanford University. They discovered that a common insect can chew sizable holes in a plastic shopping bag within 40 minutes. But a team of European scientists may have found a unique solution to the plastic problem. Each year, the world produces 300 million tons of plastic, much of which resists degradation and ends up polluting every corner of the globe.
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