Researchers led by Northwestern University have unlocked how certain wastewater bacteria can degrade plastic into food, opening avenues for innovative pollution solutions.
After years of observing plastic consumption by environmental bacteria in urban waterways, a research team led by Northwestern University has unveiled how certain bacteria break down plastic waste for sustenance. This breakthrough could offer a revolutionary method to tackle the burgeoning plastic pollution problem.
The study, recently published in the journal Environmental Science & Technology, elucidates the process employed by the bacteria Comamonas, which reside in wastewater. The bacteria first break plastic into nanoplastics, then further degrade these pieces using a specialized enzyme. Remarkably, they utilize the carbon rings from the plastic as a food source.
“We have systematically shown, for the first time, that a wastewater bacterium can take a starting plastic material, deteriorate it, fragment it, break it down and use it as a source of carbon,” lead author Ludmilla Aristilde, an associate professor of environmental engineering at Northwestern’s McCormick School of Engineering, said in a news release.
Potential Impact
Plastic pollution is a critical environmental challenge.
Polyethylene terephthalate (PET), commonly used in food packaging and beverage bottles, is especially problematic due to its persistent nature. PET represents 12% of global plastic usage and accounts for roughly half of microplastics found in wastewaters.
This research builds upon previous findings by Aristilde’s team, which demonstrated the ability of Comamonas testosteroni to metabolize simple carbons from degraded plants and plastics. By delving into how C. testosteroni interacts with PET, this study reveals more about the bacterium’s degrading abilities.
“It’s important to note that PET plastics represent 12% of total global plastics usage,” Aristilde added. “And it accounts for up to 50% of microplastics in wastewaters.”
How They Did It
Using a combination of theoretical and experimental approaches, the researchers first grew the bacteria on PET films and pellets. Advanced microscopy helped them observe changes to the plastic’s surface over time. They then found evidence of tiny nanoplastic particles in the surrounding water, indicating degradation.
“In the presence of the bacterium, the microplastics were broken down into tiny nanoparticles of plastics,” added Aristilde. “We found that the wastewater bacterium has an innate ability to degrade plastic all the way down to monomers, small building blocks which join together to form polymers. These small units are a bioavailable source of carbon that bacteria can use for growth.”
By employing omics techniques, the team pinpointed a specific enzyme that C. testosteroni expressed when exposed to PET. Using cells unable to express this enzyme, the researchers found that the bacterium’s plastic-degrading ability was significantly reduced.
Understanding Plastic’s Life Cycle
The implications of this study extend beyond potential bioremediation techniques.
It offers insight into how plastics evolve in wastewater environments. Many people assume nanoplastics enter wastewater treatment plants already in their fragmented form. However, this research indicates microbial activity in wastewater treatment processes contributes to the formation of nanoplastics.
“Wastewater is a huge reservoir of microplastics and nanoplastics,” said Aristilde. “Most people think nanoplastics enter wastewater treatment plants as nanoplastics. But we’re showing that nanoplastics can be formed during wastewater treatment through microbial activity.”
This new understanding of plastic’s journey from wastewater to natural water bodies could reshape strategies for managing plastic pollution.
Conclusion
As society grapples with the dire consequences of plastic pollution, this breakthrough offers a glimmer of hope. Harnessing the plastic-degrading capabilities of wastewater bacteria like Comamonas could be a game-changer in our efforts to create a more sustainable environment.