Animals May Hold a Hidden Key to Nature’s Carbon Cycle

Scientists in protective suits using a microscope in a laboratory — Photo: Gorodenkoff / Shutterstock

Animals across nine major groups carry enzymes that break down a natural “bioplastic,” suggesting a hidden food link between microbes and animals in many habitats.

Story Highlights

Researchers found PHA-degrading enzymes in more than 66 animal species across nine phyla.
Lab tests showed enzymes from a sponge, an earthworm, and a springtail can break down microbial PHAs.
A gutless marine worm hosts a PHA-degrading enzyme that likely helps it use this carbon source.
Experts warn not to confuse microbial PHAs with human-made plastics; terms like “bioplastic” are often misused.

What Scientists Discovered About Animal Enzymes

Scientists reported that many animals make enzymes that can break down polyhydroxyalkanoates, or PHAs. PHAs are natural polyesters that many microbes make to store carbon and energy. The team found related enzymes across more than 66 animal species and nine animal phyla, from marine worms and starfish to land animals like earthworms. This points to a broad, ancient link in food webs. The finding centers on enzyme genes in animal genomes, not on modern plastic trash or cleanup claims.

Researchers also ran simple lab tests to confirm that these enzymes work. Enzymes taken from a sponge, an earthworm, and a springtail broke down microbial PHA material under controlled conditions. That matters because it moves the claim from only gene presence to proven activity. The tests do not say how fast these enzymes work in the wild. But they show that very different animals can turn stored microbial “plastic” back into usable building blocks.

Evidence From A Gutless Worm And Older Enzyme Clues

One line of primary research tied the story to a specific animal host. Work on the gutless worm Olavius algarvensis identified a PHA-degrading enzyme in the animal and argued the worm likely benefits from PHA breakdown near its body. This points to a direct use of that carbon source by an animal host that lacks a gut and relies on symbionts and nearby chemistry. It shows how PHA breakdown could fit a real life strategy in the sea floor.

Older studies offered a separate clue about animal ability to attack PHAs. In 2016, scientists showed that pancreatic extracts from mouse and chicken could break down a PHA copolymer film. They flagged “lipase-like” activity behind the effect. Those tests used organ extracts, not whole animals feeding in nature. Still, they signaled that animal enzymes can act on PHA bonds, which fits the newer gene and lab activity findings from many species.

Why This Matters For Ecology And Industry

Microbes store carbon as PHAs in soils, sediments, and biofilms. If animals can tap that reserve, energy can move through food webs in a way scientists had not mapped well. The new study suggests this link spans many animal groups and habitats, from the seafloor to land. That could change how models treat detritus and microbial carbon. It may also affect how we view soil health, sediment cycles, and how life copes with feast and famine periods.

The work also touches industry talk about “bioplastics.” PHAs are natural polyesters that can biodegrade under the right conditions. Some firms already make PHA-based products. But experts stress that terms like bio-based, biodegradable, and compostable are not the same. Public messaging often blurs them, which breeds confusion and bad policy. Clear language helps people avoid assuming that all plastics, or even all “bioplastics,” behave like PHAs in the environment.

Avoiding Misreads And Keeping To The Facts

This research shows animals can break down microbial PHAs and sometimes gain from it. It does not claim animals digest common consumer plastics like polyethylene or polyethylene terephthalate. It also does not prove how much of an animal’s diet comes from PHA in the wild. The best-supported facts here are enzyme genes across many animals, lab-confirmed activity in three distant species, and a detailed case in a gutless worm. Future field work can measure real-world impact.

For readers who feel let down by muddled science claims, this is a reminder to demand clarity. Scientists are mapping a natural carbon loop that may have shaped life for ages. Policymakers and companies should not twist that into a promise that “nature eats our plastic.” PHAs are a special case with real promise, but also real limits. Good science can inform smarter rules and products. Clear terms can protect communities, taxpayers, and the environment from costly mistakes.