Plastic makes great food packaging. It's waterproof and flexible. And best of all, it's impervious to all known bacteria — until now. Researchers have found a bacterium in the debris fields around a recycling plant in Japan that can feed off a common type of plastic used in clothing, plastic bottles and food packaging.
The bacterium is a new species called Ideonella sakaiensis, named for the Japanese city Sakai where it was found growing on plastic debris made from a type of plastic called PET or polyethylene terephthalate. "It's the most unique thing. This bacterium can degrade PET and then make their body from PET," says Shosuke Yoshida, a microbiologist at Kyoto University and lead author on the study published in Science on Thursday.
Most plastics are insurmountable obstacles for microbes because plastics are large chains of repeating molecules called polymers. The entire chain is far larger than the individual microbe. "So the organism can't take it inside the cell to metabolize it," says John Coates, a microbiologist at the University of California, Berkeley who was not involved with the work. Imagine a baby trying to eat an enormous pizza from the middle. It can't do it. The pie is too big.
But Ideonella sakaiensis, which we here at NPR have decided to call "the polymer chomper," has two enzymes that can slice and dice the plastic polymer into smaller pieces. In other words, the baby gets a pizza cutter. The bacterium can then take the pieces and eat them, eventually converting the plastic into carbon dioxide and water.
After Yoshida and his colleagues isolated the polymer chomper, they were able to watch it disintegrate a plastic film in about six weeks. It would be great if we could culture the bacteria, spray landfills down with them and let them deal with our mountains of plastic refuse. But alas, that may never happen. "It grows very fast," Yoshida explains, "but it's likely not so useful in the field" because it chomps very slowly.
And if getting rid of our plastic waste were so easy, Coates notes, the bacterium would likely have already been found in landfills and anywhere you find mounds of plastic waste.
But with more research, Coates thinks that the bacterium might be engineered for such a purpose. "It's certainly a move in the right direction. Having an organism that seems to be capable of biodegrading these components directly will help us develop a bioremediation technology," he says. Certain species of fungi have been found to be able to degrade plastics before, though none have been converted to landfill-munching purposes. The polymer chomper offers new hope, Coates says, because bacteria are easier to work with and engineer.
That doesn't mean we'll ever be able to toss our plastic without care. Recycling will likely remain a better option anyway, Coates adds. "Environmentally, I would prefer recycling if it can be optimized and improved," he says. Biodegrading materials still releases carbon dioxide into the atmosphere, which would contribute to global warming. But in cases where recycling is not feasible, he says, maybe this little bacterium could one day prove a useful alternative.