Researchers have identified a species of bacteria that uses just two enzymes to break down plastic. Poly(ethylene terephthalate), or PET, is a type of polymer used in plastic that is highly resistant to biodegradation.
About 56 million tons of PET was produced worldwide in 2013 alone, and the accumulation of PET in ecosystems around the globe is increasingly problematic. To date, very few species of fungi - but no bacteria - have been found to break down PET. Here, Yoshida et al. collected 250 samples of PET debris and screened for bacterial candidates that depend on PET film as a primary source of carbon for growth. They identified a novel bacterium, which they named Ideonella sakaiensis 201-F6, which could nearly completely degrade a thin film of PET after six weeks at a temperature of 30°. Further investigation identified an enzyme, ISF6_4831, which works with water to break down PET into an intermediate substance, which is then further broken down by a second enzyme, ISF6_0224. These two enzymes alone can break down PET into its simpler building blocks. Remarkably, these enzymes seem to be highly unique in their function compared to the closest related known enzymes of other bacteria, raising questions of how these plastic-eating bacteria evolved. A Perspective by Uwe Bornscheuer describes these findings in greater detail.