Scientists have discovered bacteria that can break down plastic deep under the ocean. These microscopic organisms use special enzymes that have evolved over time to digest the synthetic materials humans have been releasing into the ocean for many years.

A worldwide study led by researchers from KAUST (King Abdullah University of Science and Technology) has shown that these marine bacteria are widespread and capable of breaking down polyethylene terephthalate (PET), a type of plastic commonly used in drink bottles, clothing, and packaging.

What makes these bacteria special is their ability to produce an enzyme called PETase, which can break down PET plastic. The scientists found a unique feature in this enzyme, known as the M5 motif, which acts like a signal, indicating when the enzyme is active and capable of breaking down plastic.

Carlos Duarte, a marine ecologist and co-leader of the study, says that this discovery helps understand how these enzymes have evolved from enzymes that already break down natural hydrocarbons in the ocean. These microbes have adapted to use a new carbon source, i.e., plastic.

How Bacteria Learned to Recycle Plastic

For many years, scientists believed that plastics, especially PET, were nearly impossible to break down naturally. However, this idea changed in 2016 when researchers found a bacterium in a Japanese recycling plant that could survive by consuming plastic. This bacterium had developed a special enzyme, PETase, that could break down plastic into smaller pieces.

But it was unclear whether ocean bacteria had developed similar abilities. Using a mix of AI technology, genetic screening, and lab experiments, Duarte's team discovered that the presence of the M5 motif made the PETase enzyme capable of breaking down PET. When they tested marine bacteria with this feature, they found that these bacteria could effectively break down plastic.

Plastic-Eating Bacteria 

To determine how common these plastic-eating microbes are, scientists collected more than 400 ocean samples from around the world. They found that nearly 80% of these samples contained bacteria with the M5 motif and functional PETase enzymes. These bacteria were found in a wide range of environments, from surface waters filled with plastic debris to deep, nutrient-poor areas more than two kilometres below the ocean's surface.

In the deep ocean, these plastic-eating microbes have a unique advantage. The ability to consume plastic gives them an important edge, allowing them to survive in places where food is scarce.

This discovery shows that nature is adapting to the pollution humans have caused on a global scale. While it is fascinating to see how these microorganisms are evolving, Duarte warns that we shouldn't be overly optimistic.

Turning a Discovery into Practical Solutions

These findings could lead to new ways of dealing with plastic waste on land. The enzymes found in the deep sea could be used to speed up plastic recycling efforts. The discovery of the M5 motif could be key to designing better enzymes that break down plastic more quickly and efficiently. If scientists can replicate and improve these natural mechanisms, we might have new tools in the fight against plastic pollution, all thanks to some of the most unexpected helpers: tiny bacteria in the deep ocean.

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