Not what you thought: animals have been "eating plastic" for hundreds of millions of years
A new study has discovered that dozens of animal species are capable of breaking down PHA, a type of natural plastic produced by bacteria. Researchers estimate that this ability has existed for hundreds of millions of years and may change the understanding of the carbon cycle in nature.
Long before humans invented bags, bottles, and packaging, nature already knew how to produce its own type of plastic — and it turns out that animals have also learned to use it as food. A new study indicates that the ability to break down "natural plastic" may be much more common than previously thought, and may have existed for hundreds of millions of years.
The study, conducted at the Max Planck Institute for Marine Microbiology in Germany and published in the journal Nature Ecology & Evolution, focused on substances called PHA — polymers that are naturally produced by bacteria and other microorganisms. For them, it is essentially a storage facility: when they receive more carbon than they need at a given moment, they store it inside the cell in the form of PHA for future use.
Until now, it was generally thought that mainly microorganisms were capable of breaking down this substance. However, the researchers discovered something surprising: many other animals possess enzymes capable of doing so.
The starting point was an unusual marine worm called Olavius algarvensis. The worm has no mouth and not even a regular digestive system. Instead, symbiotic bacteria live under its skin, which it digests to obtain the necessary nutrients. The researchers discovered that one of these bacteria stores large amounts of PHA. At the same time, an enzyme was found in the worm's body capable of breaking down the substance into smaller molecules that it can utilize.
But then came the real surprise. When the team expanded the search, similar enzymes were found in more than 66 species belonging to nine different groups of animals. Among others, the ability was found in sponges, earthworms, and tiny animals living in the soil. According to the researchers, this means that it is not a unique trick of a strange marine creature, but an ability that may be widespread throughout the animal kingdom.
PHA is also known to industry. Today, bacteria are grown in fermentation tanks and encouraged to produce large amounts of the substance, which can be turned into biodegradable plastic. It is used, among other things, in food packaging, hygiene products, agriculture, and even in medical applications such as absorbable sutures and drug delivery systems.
Its great advantage is that it degrades through natural biological processes, unlike many types of plastic derived from petroleum. The new findings may also change the way scientists look at the carbon cycle in nature. If animals are indeed breaking down PHA on a large scale, it is possible that they play a previously unknown role in transferring the carbon stored by bacteria into the food chain.
The researchers do not yet know how significant this process is in nature, but they raise a particularly intriguing possibility: animals may have been "eating" natural plastic for hundreds of millions of years — and only now are we beginning to understand it.
