In a damning indication of Earth's pollution problem, scientists have discovered that microbes around the world have gained a taste for plastic. 

Reporting in the journal Microbial Ecology, scientists at Chalmers University of Technology in Sweden found that the number of microbial enzymes that can degrade plastic is on the rise and it directly correlates with growing levels of plastic pollution. In other words, areas that suffer from more plastic pollution appear to have more plastic-munching microbes in their soil and seas. 

This, the study authors argue, strongly hints that microbial life is evolving to cope with plastic pollution on a global scale.

“Currently, very little is known about these plastic-degrading enzymes, and we did not expect to find such a large number of them across so many different microbes and environmental habitats. This is a surprising discovery that really illustrates the scale of the issue,” Jan Zrimec, first author of the study, said in a statement.

To reach these findings, the researchers analyzed data on microbial DNA in samples from 236 locations around the world, specifically looking for genes that code for plastic-degrading enzymes. In total, they found 30,000 enzymes – 12,000 in the ocean microbiome and 18,000 in the soil – with the potential to degrade 10 different types of plastic.

“Using our models, we found multiple lines of evidence supporting the fact that the global microbiome's plastic-degrading potential correlates strongly with measurements of environmental plastic pollution – a significant demonstration of how the environment is responding to the pressures we are placing on it,” adds Aleksej Zelezniak, study author and Associate Professor in Systems Biology at Chalmers.

Around 8 million tons of plastic flood into the world’s oceans each year. Mass-production of plastics only really kicked off in the latter half of the 20th century, but this human-made material has become prolific in the natural environment within just a few decades. From Antarctic ice to the depths of the Mariana Trench, there’s now scarcely a natural environment on Earth that’s remained unscathed by plastic pollution. One of plastic’s main appeals is its resilience, but this also means that it persists in the environment for a long time before degrading. A plastic straw, for example, could take up to 200 years to decompose.

Notwithstanding the scale of the issue at hand, the researchers of this latest project believe that their work could potentially be used to discover and adapt enzymes for novel recycling processes to help address this global pollution problem.

“The next step would be to test the most promising enzyme candidates in the lab to closely investigate their properties and the rate of plastic degradation they can achieve. From there you could engineer microbial communities with targeted degrading functions for specific polymer types,” explains Zelezniak.