A plastic bag sat intact on the ocean floor 6 kilometers below the surface of the Mariana Trench — until scientists found it and realized something unexpected: life down there may be learning to eat it.
Over 150 million metric tons of plastic have ended up in the ocean since 1950. Most of it stays there, fragmenting into smaller pieces but never truly disappearing. Yet researchers have now discovered that ocean bacteria in the deep sea are developing the genetic tools to break down and metabolize plastic as a food source.
Microbes finding a way
Scientists led by Carlos Duarte at King Abdullah University of Science and Technology analyzed 415 water samples from oceans worldwide. In more than 75% of them, they found genetic sequences associated with PETase — an enzyme that can break down PET plastic, the polymer used in drink bottles and clothing. The bacteria producing these enzymes appear to have evolved spontaneously in response to an abundance of a new resource: the plastic we've dumped into their habitat.
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Start Your News Detox"In the ocean, where carbon is scarce, microbes seem to have fine-tuned these enzymes to make use of this new, human-made carbon source: plastic," Duarte explained. This isn't entirely new territory. In 2016, Japanese scientists discovered bacteria in a plastic recycling plant capable of degrading PET. That finding sparked a global search for other plastic-eating microbes, driven by both scientific curiosity and the hope that these organisms could improve industrial recycling.
What's significant now is the scale. Finding PETase-producing bacteria in three-quarters of global ocean samples suggests this isn't a rare accident — it's becoming widespread. These enzymes are evolving across different bacterial species in different parts of the world, which means the genetic blueprint for plastic degradation is spreading through marine ecosystems.
The catch
Before this feels like a solution, Duarte was careful to add a crucial caveat: "By the time plastics reach the deep sea, the risks to marine life and human consumers have already been inflicted." The bacteria breaking down plastic in the deep ocean doesn't undo the damage done when that plastic was floating through the water column, tangling in gills and filling stomachs. It doesn't reverse the microplastics now present in fish and in human bloodstreams.
What this discovery does offer is a model. The enzymes these bacteria have evolved could be studied, optimized in laboratories, and potentially used to improve how we recycle plastic on land — where we might actually prevent it from reaching the ocean in the first place. The microbes haven't solved ocean plastic pollution. But they've shown us one possible direction for how we might.
[Study: Alam, et. al. "Widespread distribution of bacteria containing PETases with a functional motif across global oceans." The ISME Journal. June 10, 2025.]
