Plastic bottles at a dump in Northern Thailand. And bacterium that can consume even one kind of plastic could become a desperately-needed ally.’ photograph: Rungroj Yongrit?EPA
Thanks to a genetically engineered enzyme, a bug that eats plastic bottles developed a much bigger appetite for our rubbish. It is a hopeful sign
Plastic bottles at a dump in northern Thailand
Plastic bottles at a dump in northern Thailand. ‘A bacterium that can consume even one kind of plastic could become a desperately needed ally.’ Photograph: Rungroj Yongrit?EPA
Evolution never sleeps. Before 1970 there can have been no significant bacteria that ate plastic, because there was not enough of that plastic in the world to sustain a population. But in 2016 a group of Japanese scientists discovered a new species, Ideonella sakaiensis, in the samples they were sifting from a bottle-recycling plant, that was able to attack and eat PET, the plastic used in most bottles, almost all of which ends up in landfill or dumped at sea, where it may last for centuries. Everything that rots in nature does so because it is being eaten by bacteria. Most plastics – among them PET – were considered totally impervious to bacterial attack, making them almost indestructible unless burned or crushed. So a bacterium that can consume even one kind of plastic could become a desperately needed ally in the struggle to stop the oceans being choked with plastic waste.
What has captured the imagination of the world is that a subsequent group of scientists, who were trying to understand on a molecular level how I sakaiensis breaks down and digests plastic bottles, found the enzymes that it uses and made a slightly different version of one to see what would happen. The new enzyme is much more efficient than the version found in nature, and works on more kinds of plastic. This kind of molecular tweaking of substances, already found in nature, is at the root of another recent scientific breakthrough, the Crispr-Cas9 technique for genetic engineering. It offers some hope that we can use technology to moderate and even to some extent to reverse the impacts that earlier technologies, such as those that make it easy to manufacture billions of tons of plastic, have had on the world around us.
This is going to be essential. The mass production and use of plastics has had such an effect on the Earth that some scientists, speculating wildly that there will still be people around to care about such things in the unimaginably distant future, have proposed the detection of plastic deposits as the best signal of the Anthropocene, the era in which human activity becomes the most powerful factor affecting life on Earth. One of the things this story shows is that our environment is not static and never has been. It is a dynamic system, in which changes of every sort have unintended consequences – PET was widely adopted partly because it seemed to have no ill effects on human health, at a time when no one asked how we would ever get rid of it – and every action produces an unexpected reaction, so that some bacteria learn to be resistant to antibiotics while others learn to feed off plastics. Even plastics have their uses to clean up pollution: they are used as sponges to clean up oil spills, although Australian scientists have just discovered a blend of sulphur and cooking oil that promises to work even better. There is no simpler world to which we can retreat – and for the sake of our children, we will simply have to manage these things better than our parents’ generations did.