Animals have been consuming nature's bioplastics for millions of years, according to groundbreaking research from the Max Planck Institute for Marine Microbiology. This revelation challenges the long-held belief that only microorganisms could break down these natural plastics, opening up a new avenue for understanding the carbon cycle and the intricate relationships between organisms. The study, published in Nature Ecology & Evolution, highlights the remarkable ability of various animals to degrade polyhydroxyalkanoates (PHAs), a type of biodegradable plastic produced by microorganisms.
The research began with an extraordinary marine worm, Olavius algarvensis, which lacks a mouth and gut but relies on symbiotic bacteria for nutrition. Scientists discovered that one of the worm's bacterial symbionts stores vast amounts of carbon as PHA. Intriguingly, the worm possesses an enzyme capable of breaking down these PHAs into smaller molecules that animals can utilize. This finding was not an isolated case; further examination of animal genomes revealed related enzymes in over 66 species across nine different phyla, including sponges, earthworms, and springtails. The versatility of these enzymes in breaking down PHAs was astonishing, as it indicated a widespread capability among animals from diverse evolutionary branches.
PHAs, produced by microorganisms, serve as energy and carbon reserves and are also used to create biodegradable plastics. In industrial settings, bacteria are cultivated in large fermentation tanks, fed with carbon-rich materials like sugars or plant oils, and encouraged to produce PHAs. These compounds can then be extracted and transformed into plastic-like materials, offering advantages such as moldability, water resistance, and stability for everyday applications. PHAs are particularly notable for their biological circularity, being both produced by microorganisms and biodegradable through biological processes.
Despite their potential, PHAs currently account for a small portion of the bioplastics market. However, the growing demand for biodegradable, bio-based materials and the expansion of global bioplastics production capacity may soon change this. The new findings add a crucial layer to the understanding of bioplastics by revealing that many aquatic and terrestrial animals possess enzymes capable of breaking down PHAs, suggesting that animals may play a significant role in the degradation of natural bioplastics alongside microorganisms.
The implications of this discovery extend beyond the realm of biology. It introduces a new perspective on the carbon cycle, suggesting that animals have been accessing microbial carbon reserves for hundreds of millions of years, a process that was previously thought to be exclusive to microorganisms. This revelation underscores the importance of continued research into unusual organisms, as they may hold the key to uncovering hidden biological processes that have been operating for eons, shaping the natural world as we know it.
