Scientists have discovered that animals may have been consuming and breaking down nature’s own biodegradable plastics for hundreds of millions of years.
Researchers from the Max Planck Institute for Marine Microbiology found that numerous animals possess enzymes capable of breaking down polyhydroxyalkanoates (PHAs), natural bioplastics produced by bacteria and other microorganisms as carbon and energy reserves.
The discovery began with an unusual marine worm, Olavius algarvensis. The worm has no mouth or digestive system and relies on bacteria living beneath its skin. Some of these bacteria store large amounts of PHA. Researchers found that the worm produces an enzyme capable of breaking down this material, allowing it to access the carbon stored inside its bacterial partners.
The team then searched more broadly and found related PHA-degrading enzymes in more than 66 animal species belonging to nine different phyla. Laboratory experiments showed that enzymes from animals as diverse as a sponge, an earthworm and a springtail could also break down PHAs.
PHAs are naturally occurring biodegradable polymers found in soils, sediments and aquatic ecosystems. Humans also manufacture them as an alternative to conventional plastics for applications including packaging, agriculture and medical products.
The finding suggests that animals may play a previously overlooked role in breaking down microbial carbon reserves. When animals consume microorganisms containing PHAs, these enzymes could help release the stored carbon and transfer it into animal food webs.
Scientists do not yet know how widespread or environmentally important this process is. However, the discovery changes the understanding of the carbon cycle by revealing that microbial bioplastics are not necessarily accessible only to microorganisms many animals may have been using them as an energy source for millions of years.
Nature developed biodegradable plastic long before humans did and animals appear to have evolved the ability to digest it too.