Lab experiment shows that bacteria really do eat and digest plastic!

bacteria Rhodococcus ruber It actually eats and digests plastic. This was demonstrated in laboratory experiments by doctoral student Maikki Guderian at the Royal Netherlands Institute for Marine Research (NIOZ). Based on a model study using plastic in synthetic seawater in a laboratory, Goudriaan calculated that bacteria can decompose about one percent of the plastic fed annually into carbon dioxide.2 and other harmless substances. “But,” Guderian asserts, “this is certainly not a solution to the plastic soup problem in our oceans. It is, however, another part of the answer to the question of where all the oceans’ ‘lost plastic’ has gone.”

special plastic

Guderian had a special plastic made specifically for these experiments with a characteristic carbon shape (13c) in it. When she fed this plastic to bacteria after pre-treating with “sunlight” — a UV lamp — in a bottle simulating seawater, she saw that the special version of the carbon appeared as carbon dioxide.2 over the water. “UV treatment was necessary because we already know that sunlight partially breaks down plastic into microscopic bacteria-sized pieces,” explains the researcher.

Proof of principle

“This is the first time we’ve demonstrated in this way that bacteria actually digest plastic and convert it into carbon dioxide2 And other molecules,” Guderian says. It was already known to be bacteria Rhodococcus ruber It can form a so-called biofilm on plastic in nature. It has also been measured that the plastic hides under this biofilm. “But now we’ve really established that bacteria actually digest plastic.”


When Goudriaan calculates the total breakdown of plastics into CO2, estimating that bacteria can break down about one percent of available plastic annually. “Maybe this is an underestimate,” she adds. “We only measured the amount of carbon-13 in carbon dioxide2, so it is not in other plastic breakdown products. There will definitely be 13C is found in many other molecules, but it’s hard to tell which part of that was broken down by the UV light and which part was digested by the bacteria. “

no solution

Although marine microbiologist Guderian is very excited about bacteria that feed on plastic, she stresses that microbial digestion is not a solution to the huge problem of all the plastic floating in and around our oceans. “These experiments are basically proof of principle. I see it as one piece of the jigsaw, on the question of where all the plastic that disappears into the oceans stays. If you try to keep track of all our waste, a lot of the plastic is lost. Digestion by bacteria could provide part of the explanation.” .

From the lab to the mudflats

To discover whether “wild” bacteria also eat plastic “in the wild”, follow-up research needs to be done. Guderian has already done some experimental experiments with real seawater and some sediments she’s collected from the bottom of the Wadden Sea. “The first results of these experiments indicate that plastic does degrade, even in nature,” she says. “A new PhD student will have to continue this work. Eventually, of course, you hope to calculate how much plastic in the oceans is actually degrading because of bacteria. But much better than cleanup, is prevention. And only we humans can do that,” Guderian says.

The sun’s rays are making plastic soup dough

Goudriaan’s colleague Annalisa Delre recently published a paper about sunlight breaking down plastic on ocean surfaces. Floating microplastics are broken down into smaller, invisible nanoplastic particles that spread across the entire water column, but also into compounds that can be completely broken down by bacteria. This is evidenced by experiments carried out in the NIOZ laboratory in Texel.

In the latest issue of Marine Pollution Bulletin, doctoral student Analisa Delery and her colleagues calculated that about 2% of floating plastic could disappear from the ocean’s surface in this way each year. “It may seem small, but year after year, it adds up. Our data shows that sunlight can consequently degrade a significant amount of all the floating plastic that has been littering the oceans since the 1950s,” says Dillery.

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