Researchers at the Royal Netherlands Institute for Sea Research (NIOZ) have proven for the first time that bacteria can digest plastic into CO₂ and other molecules. They developed a method to determine how much plastic microbes process, using carbon isotopes. They published their results in Marine Pollution Bulletin.

Some of the plastic that ends up in the oceans seems to disappear. NIOZ researchers are looking for an explanation for this. In early January, they showed that plastic in the oceans partially breaks down under the influence of sunlight. Now research by PhD student Maaike Goudriaan and others shows that the bacterium Rhodococcus ruber can digest polyethylene, albeit at a very low rate (~1.2% per year of the initial amount of polyethylene (22.2 mg per L)).

Goudriaan had plastic fabricated with carbon-13 and pre-treated it with a UV lamp. She then fed it to bacteria in a bottle of replicated seawater. CO₂ containing ¹³C was created and the carbon isotopes entered the bacteria’s membrane lipids. According to Goudriaan, we can use this knowledge to improve the model for plastic degradation. ‘It is not a solution to the problem of the plastic soup in the oceans,’ she says in a press release from NIOZ. ‘It does partially answer the question as to where all the lost plastic in the oceans has gone.’