Bacteria can use plastic waste as a food source, which isn’t as good as it sounds: ScienceAlert

Bacteria can use plastic waste as a food source, which isn’t as good as it sounds: ScienceAlert

Bacteria can use plastic waste as a food source, which isn’t as good as it sounds: ScienceAlert

Plastic pollution has gotten out of hand. More than every year 8 million tons of synthetic polymers ends up in the ocean, and while some sinks to the floorreturns to the coastor collects in the in the middle of no man’s landa significant portion is not so easy to explain.

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

Experiments in the laboratory have now shown that a type of marine bacteria known as Rhodococcus redcan slowly break down and decompose the plastic it is made of polyethylene (PE).

Largely used in packaging, PE is the most widely produced plastic in the world, and although it is not clear if R. ruber chews on this detritus in the wild, the new research confirms it is at least capable of doing so.

Previous studies have found tribes from R. ruber floating in dense cellular films on marine plastic. In fact, first survey in 2006 suggested the plastic underneath R. ruber broke faster than usual.

The new study confirms that this is the case.

“This is the first time we have proven in this way that bacteria actually digest plastic into CO2 and other molecules.” say microbial ecologist Maaike Goudriaan from the Royal Netherlands Institute for Sea Research (NIOZ).

To mimic the natural ways plastic decomposes on the ocean surface, Goudriaan and her colleagues exposed their plastic samples to UV light and placed them in artificial seawater.

“The treatment with UV light was necessary because we already know that sunlight partially breaks down plastic into bite-sized chunks for bacteria.” explains Goudrian.

Then the team introduced a strain of R. ruber to the scene.

By measuring levels of an isotope of carbon released from decomposing plastic called carbon-13, the authors estimated that the polymers in their experiments broke down at a rate of about 1.2 percent per year.

The team isn’t sure how much the UV lamp did to the plastic compared to the activity of the microbes, but the bacteria clearly played a role. Post-experiment bacterial samples showed fatty acid membranes enriched in carbon-13.

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

“Our data shows that sunlight could have broken down a substantial portion of all floating plastic that has entered the oceans since the 1950s.” say microbiologist Annalisa Delre.

Microbes may then have come in and consumed some of the sun’s remnants.

Since 2013, researchers have warned that microbes likely thrive in plastic patches in the ocean, forming a synthetic ecosystem that has come to be known as a “plastisphere.”

There is even evidence that some of these microbial communities are adapting to eat different types of plastic.

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

Some scientists have proposed releasing plastic-chewing equivalents at pollution hotspots, such as the Large Pacific Garbage Patch.

Others are not so sure if that’s a good idea. engineered enzymes and bacteria breaking down plastic may sound like a great way to make our waste disappear, but some experts worry about unintended side effects on natural ecosystems and food webs.

After all, breaking down plastic is not necessarily a good thing. Microplastics are much more difficult to clean up than larger pieces, and these tiny remnants can enter food webs. For example, filter feeders can accidentally grab small pieces of plastic before microbes do.

In a study by 2020, every single sample of seafood tested in an Australian market contained microplastics.

What that does to human or animal health is completely unknown.

“Much better than cleaning up is prevention”, argues Goudrian.

“And only we humans can do that.”

The study is published in Marine Pollution Bulletin.

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