Plastic Biodegradation by the Global Ocean Microbiome

Marine plastic pollution is a massive environmental crisis, with an estimated 8 million tons of plastic waste entering the oceans each year. While some microbes can break down certain plastics, a new study finds no clear correlation between plastic pollution levels in the global oceans and the expression of genes that could degrade plastic by marine microorganisms.

The research, published in the journal Environmental Microbiome, analyzed metatranscriptomic data from hundreds of ocean samples collected during the Tara Oceans project. The scientists looked for transcripts of genes encoding enzymes thought to have plastic-degrading abilities, based on a comprehensive database called PlasticDB.

"Our research contributes to understanding the complex global relationship between plastic pollution and microbial plastic degradation potential," says lead author Victor Gambarini from the University of Auckland. "We reveal that the transcription of putative plastic-degrading genes in the global ocean microbiome does not correlate to marine plastic pollution."Even when the researchers looked at specific ocean regions, depths, or plastic types, they found very few significant correlations with the relative abundance of possible plastic-degrading enzymes.

Surprisingly, the relatively pristine waters around Antarctica showed some of the highest levels of transcripts linked to plastic breakdown, suggesting this region could be a promising source of new plastic-degrading enzymes.

Overall, the findings indicate the global ocean microbiome has not yet evolved to efficiently degrade the many types of plastic pollution plaguing marine ecosystems. However, the researchers caution that microbial adaptation to new food sources can be very slow on an evolutionary timescale.

"Our study highlights the ongoing danger that plastic poses to marine environments threatened by plastic pollution," says senior author Gavin Lear. "Developing solutions will likely require a combination of dramatically reducing new plastic waste, recovering existing ocean plastic, and potentially harnessing microbes through approaches like enzyme engineering.

"While disappointing from an environmental remediation perspective, the lack of widespread microbial plastic degradation showcases both the durability of synthetic polymers and the vast challenges facing efforts to clean up the oceans using nature's tools alone. A multi-pronged approach will be needed to tackle this persistent pollution problem.

The paper was published in the journal Environmental Microbiome and can be accessed at: doi.org/10.1186/s40793-024-00575-4