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Researchers have long observed that a common family of environmental bacteria, Comamonadacae, grow on plastics littered throughout urban rivers and wastewater systems. But exactly what these Comamonas bacteria are doing has remained a mystery.

Now, Northwestern University-led researchers have discovered how cells of a Comamonas bacterium are breaking down plastic for food. First, they chew the plastic into small pieces, called nanoplastics. Then, they secrete a specialized enzyme that breaks down the plastic even further. Finally, the bacteria use a ring of carbon atoms from the plastic as a food source, the researchers found.

The discovery opens new possibilities for developing bacteria-based engineering solutions to help clean up difficult-to-remove plastic waste, which pollutes drinking water and harms wildlife.

The study is published in the journal Environmental Science & Technology.

"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," said Northwestern's Ludmilla Aristilde, who led the study. "It is amazing that this bacterium can perform that entire process, and we identified a key enzyme responsible for breaking down the plastic materials. This could be optimized and exploited to help get rid of plastics in the environment."

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