Saudi researchers discover evolution of ‘Plastic-Eating Bacteria’ across oceans

A global survey led by researchers at Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) has uncovered how ocean-dwelling microbes (bacteria) are evolving to digest plastic waste.

Published in The ISME Journal, the study reveals that bacteria across the world’s oceans carry a genetic signature—the “M5 motif”—on a key enzyme called PETase, which enables them to break down polyethylene terephthalate (PET), the plastic used in bottles, packaging, and clothing.

“The M5 motif acts like a fingerprint showing when a PETase is functional,” explained Carlos Duarte, marine ecologist and co-leader of the study. “It reveals how these enzymes evolved from other hydrocarbon-degrading enzymes to exploit plastic as a new carbon source.”

Long considered indestructible in nature, PET first showed signs of biodegradation in 2016 when scientists found bacteria in a Japanese recycling plant that had evolved PETase to digest plastic. Whether similar enzymes existed in marine environments, however, remained unknown—until now.

By combining AI-based structural modeling, global genetic screening, and laboratory tests, Duarte’s team demonstrated that bacteria with the complete M5 motif can efficiently degrade PET. Gene activity data further confirmed that these enzymes are actively expressed in plastic-polluted waters worldwide.

The team analyzed over 400 ocean samples, finding M5-bearing PETases in nearly 80% of sites—from garbage-laden surface gyres to nutrient-poor depths two kilometers below. In deep-sea regions, researchers believe the ability to consume synthetic carbon could offer microbes a vital survival advantage.

While these ‘plastic recycler’ microbes highlight nature’s adaptive resilience, Duarte warns they are no quick fix: “By the time plastics reach the deep sea, the damage is already done.” Yet, the research head adds that understanding the M5 motif could accelerate industrial enzyme design, inspiring new technologies for efficient, closed-loop plastic recycling—and perhaps, one day, enlist the ocean’s own microbes in the cleanup effort.