Bacteria can use plastic waste as a food source, and it's not as good as it sounds

Bacteria can use plastic waste as a food source, and it’s not as good as it sounds

Plastic Pollution Is Out of Control Every year, more than 8 million tons of synthetic polymers enter the ocean, and while some of them sink into the ground, make their way back to the beach, or collect in the middle of nowhere, a significant portion is not easily accounted for.

All that missing plastic is a mystery, but some researchers suspect that hungry microbes are partly responsible.

Experiments in the lab have now shown that a type of marine bacteria known as Rhodococcus ruberIt can slowly decompose and digest plastics made of polyethylene (PE).

largely used in packaging, Polyethylene is the most widely produced plastic in the world, and while it is not clear whether Roper On these litters in the wild, the new research confirms that they are able to do at least that.

Previous studies have found strains of Roper They float in dense cellular membranes on marine plastic. Furthermore, preliminary research in 2006 suggested that there was plastic material underneath Roper It was collapsing at a faster rate than usual.

The new study confirms that this is the case.

“This is the first time we’ve demonstrated in this way that bacteria actually digest plastic into carbon dioxide and other molecules,” says microbial ecologist Maikki Guderian of the Royal Netherlands Institute for Marine Research (NIOZ).

To simulate the natural ways that plastic decomposes at the ocean’s surface, Guderian and her colleagues exposed their plastic samples to ultraviolet light and placed them in artificial seawater.

“The UV treatment was necessary because we already know that sunlight partially breaks down plastic into microscopic bacteria-sized pieces,” Gudrian explains.

After that, the team introduced a strain of Roper to the scene.

By measuring the levels of a carbon isotope released from the degrading plastic called carbon-13, the authors estimated that the polymers in their experiments degrade at a rate of 1.2% per year.

The team can’t be sure how much the plastic was eroded by the UV lamp compared to the microbial activity, but it’s clear that bacteria played a role. Bacterial samples after the experiment showed carbon-13-enriched fatty acid membranes.

The rate of plastic decay identified in the current study is too slow to completely solve the problem of plastic pollution in our oceans, but it does point to where some of our planet’s lost plastic may have gone.

“Our data shows that sunlight could have thus degraded a significant amount of all the floating plastic that has been littering the oceans since the 1950s,” says microbiologist Annalisa Delery.

Microbes can then come in and digest some of the sun’s leftovers.

Since 2013, researchers have been warning that microbes are likely to thrive on plastic patches in the ocean, forming an artificial ecosystem that has come to be known as a plastisphere.

There is even evidence to suggest that some of these microbial communities are adapted to eating different types of plastic.

Previous studies have identified specific bacteria and fungi, both on land and at sea, that appear to feed on plastic. But while this knowledge could help us better recycle our waste before it ends up in the wild, its other uses are controversial.

Some scientists have suggested releasing plastic-chewing equivalents in pollution hotspots, such as the Great Pacific Garbage Patch.

Others aren’t so sure this is a good idea. Engineered enzymes and bacteria that break down plastic might sound like a great way to make our waste disappear, but some experts worry about unintended side effects of natural ecosystems and food webs.

After all, breaking plastic isn’t necessarily a good thing. Microplastics are much more difficult to clean than large pieces, and these small residues can infiltrate food webs. Filter feeders, for example, may accidentally pick up small pieces of plastic before microbes do.

In a study conducted in 2020, every sample of seafood tested at a market in Australia contained microplastics.

What this does to human or animal health is not fully known.

“Prevention is much better than cleanup,” says Gudrian.

“And only we humans can do that.”

The study has been published in Marine Pollution Bulletin.

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