“scientists identified more than 200 plastic-degrading fungi + bacteria” – credit: Irina Druzhinina and Feng Cai

Plastic-eating fungi thriving in man-made ‘plastisphere’ may help tackle global waste
by Royal Botanic Gardens, Kew  /  May 17, 2023

“A new study published in the Journal of Hazardous Materials by researchers at the Royal Botanic Gardens, Kew, and partners has identified a diverse microbiome of plastic-degrading fungi and bacteria in the coastal salt marshes of Jiangsu, China. The international team of scientists counted a total of 184 fungal and 55 bacterial strains capable of breaking down polycaprolactone (PCL), a biodegradable polyester commonly used in the production of various polyurethanes. Of these, bacterial strains within the genera Jonesia and Streptomyces have the potential to further degrade other petroleum-based polymers—natural or synthetic chains of molecules bound together. The plastic-degrading microorganisms were sampled in May 2021 from Dafeng in eastern China, a UNESCO-protected site near the Yellow Sea Coast. The sampling confirmed the presence of a terrestrial plastisphere, a term that is relatively new to terrestrial ecology as past studies have primarily focused on marine environments. The microbiome of this “man-made ecological niche” of coastal plastic debris was further found to be distinct from the surrounding soil.

Scientists are increasingly looking at microorganisms, such as fungi and bacteria, to help tackle some of the most pressing challenges of the modern age, including the rising tide of plastic pollution. According to the United Nations Environment Program (UNEP), 400 million tons of plastic waste is produced annually, with a steep increase in levels of plastic pollution since the 1970s. Researchers are, however, hopeful that answers to this problem could be found in the plastisphere. Past research has already recognized the potential of microorganisms to tackle plastic waste; a 2017 study led by researchers from China and Pakistan identified a strain of the fungi Aspergillus tubingensis that was breaking down plastic at a landfill in Islamabad, Pakistan. To date, 436 species of fungi and bacteria have been found to degrade plastic and Kew scientists and partners believe their latest findings could lead to the development of efficient enzymes designed to biologically degrade plastic waste.

The Research arrives ahead of World Environment Day 2023 on June 5, the theme of which is finding solutions to the plastic waste crisis under the campaign of #BeatPlasticPollution. Dr. Irina Druzhinina, Senior Research Leader in Fungal Diversity and Systematics at RBG Kew, says, “Microbiologists across the board feel responsible for finding solutions to the ecologically friendly treatment of plastic waste because bacteria and fungi will be the first organisms to learn how to deal with this new material. We have no doubt that microbes will figure out ways to effectively degrade plastic, but this may take thousands of years if we leave nature to run its course. That is why our task is to utilize the knowledge we already possess of microbial biology, to speed up and direct the evolution of microbes and their individual genes to do the job now.”

Because of their longevity and hydrophobic surface, plastics in aquatic ecosystems have created a ‘microbial reef’ of sorts for fungi and bacteria to attach to. And in the case of certain biodegradable plastics, they can provide microbes with a source of carbon to metabolize—a food source. At Dafeng, the researchers collected 50 samples of plastic waste from seven different types of petroleum-based polymers: polyethylene terephthalate (PET), expanded polystyrene (EPS), polyethylene (PE), polyurethane (PU), polyamide (PA), polypropylene (PP), and polyvinyl chloride (PVC). Among the samples, the researchers identified 14 genera of fungi, including the plant pathogens Fusarium and Neocosmospora. Plant-pathogenic fungi draw their nutrients from plants but do so in a way that harms their host. The study’s findings indicate these fungi may be better at degrading PCL plastics and other synthetic polymers than saprotrophic fungi—fungi that feed on dead plant and animal remains.

“The study has confirmed the presence of a ‘terrestrial plastisphere’ ecosystem. The microbiome of this plastisphere was found to be distinct from the surrounding soil” credit: Irina Druzhinina and Feng Cai

Dr. Druzhinina adds, “The ecological niche of the Dafeng salt marshes is precisely why we chose to investigate the microbial communities present in the plastic waste there, and so far our findings have proven to be both exciting and promising.” In the wild, fungi play a key role in breaking down organic matter and moving it through the carbon cycle. Over millions of years, the ability to break down many complex and naturally occurring polymers, such as cellulose, has evolved. In fact, the enzymes secreted by fungi are extremely efficient at breaking down complex organic compounds, including carbohydrates and proteins. Alongside the fungi at Dafeng, the research team recognized two genera of bacteria, Streptomyces and the recently discovered genus Jonesia, as promising candidates for plastic degradation.

In particular, the species Jonesia cf. Quinghaiensis dominated the 55 sampled bacterial strains. Xuesong Li, Master’s Student at Nanjing Agricultural University, China, says, “The opportunity to work on a project with potentially impactful solutions to tackling rising levels of plastic pollution across the globe was an immediate draw, particularly as this was my first research project. There was some initial concern we might not gather enough data from a single sampling, but the results so far have been overwhelming, and we have had to restrain ourselves from isolating more and more cultures to study their characteristics. And though bacteria proved highly active in this regard, I personally favored working with fungi, as these organisms have vast potential for applications far beyond the degradation of plastic.”

“global distribution of microplastics according to size in millimeters

Despite the many exciting developments made in the field, the study’s authors warn that our understanding of plastic – associated microorganisms is still in its infancy. Many questions about these ecological niches remain unanswered and the study’s authors faced some limitations in precisely identifying the analyzed strains down to a species level. Dr. Feng Cai, Sun Yat-sen University in Shenzhen, China, says, “What strikes me the most is the sheer power of microbial diversity, especially if you consider how challenging it is to detect them; they are microscopic in size, secretive in nature, and simple in appearance.

“colony of limpets attached to diving mask found washed ashore on beach”

However, when we shift our perspective and view them through a biochemical lens, we gain access to an abundant complexity that awaits our exploration. It is truly exhilarating to realize we have barely scratched the surface and have already discovered a wealth of potentially promising resources for future technologies. This realization fills me with an incredible sense of satisfaction, knowing that there are numerous discoveries still to be made and that our work can potentially lead to significant advancements in the field.”

RBG Kew is home to one of the oldest and biggest fungaria in the world with more than 1.25 million specimens, but the kingdom of fungi remains one of the great big mysteries of the natural world. Estimates vary but there could be several million species yet to be discovered on top of the more than 144,000 species described to date, and scientists are positive that among them are new sources of food, medicine, and other beneficial compounds.”

More information: Guan Pang et al, The distinct plastisphere microbiome in the terrestrial-marine ecotone is a reservoir for putative degraders of petroleum-based polymers, Journal of Hazardous Materials (2023). DOI: 10.1016/j.jhazmat.2023.131399

“plastisphere microbes go to sea on flotsam fragments”

The Ocean’s Biggest Garbage Pile Is Full of Floating Life
by Annie Roth / May 6, 2022

“In 2019, the French swimmer Benoit Lecomte swam over 300 nautical miles through the Great Pacific Garbage Patch to raise awareness about marine plastic pollution. As he swam, he was often surprised to find that he wasn’t alone. “Every time I saw plastic debris floating, there was life all around it,” Mr. Lecomte said. The patch was less a garbage island than a garbage soup of plastic bottles, fishing nets, tires and toothbrushes.

And floating at its surface were blue dragon nudibranchs, Portuguese man-o-wars, and other small surface-dwelling animals, which are collectively known as neuston. Scientists aboard the ship supporting Mr. Lecomte’s swim systematically sampled the patch’s surface waters. The team found that there were much higher concentrations of neuston within the patch than outside it. In some parts of the patch, there were nearly as many neuston as pieces of plastic.

“I had this hypothesis that gyres concentrate life and plastic in similar ways, but it was still really surprising to see just how much we found out there,” said Rebecca Helm, an assistant professor at the University of North Carolina and co-author of the study. “The density was really staggering. To see them in that concentration was like, wow.” The findings were posted last month on bioRxiv and have not yet been subjected to peer review. But if they hold up, Dr. Helm and other scientists say, it may complicate efforts by conservationists to remove the immense and ever-growing amount of plastic in the patch.

“Lecomte’s team is only in the eastern section, estimated twice the size of Texas

The world’s oceans contain five gyres, large systems of circular currents powered by global wind patterns and forces created by Earth’s rotation. They act like enormous whirlpools, so anything floating within one will eventually be pulled into its center. For nearly a century, floating plastic waste has been pouring into the gyres, creating an assortment of garbage patches. The largest, the Great Pacific Patch, is halfway between Hawaii and California and contains at least 79,000 tons of plastic, according to the Ocean Cleanup Foundation. All that trash turns out to be a great foothold for living things.

“sea life has attached itself to this plastic bottle fished out of the ocean” @osleston

Dr. Helm and her colleagues pulled many individual creatures out of the sea with their nets: by-the-wind sailors, free-floating hydrozoans that travel on ocean breezes; blue buttons, quarter-sized cousins of the jellyfish; and violet sea-snails, which build “rafts” to stay afloat by trapping air bubbles in a soap-like mucus they secrete from a gland in their foot. They also found potential evidence that these creatures may be reproducing within the patch. “I wasn’t surprised,” said Andre Boustany, a researcher with the Monterey Bay Aquarium in California. “We know this place is an aggregation area for drifting plastics, so why would it not be an aggregation area for these drifting animals as well?”

“discarded, tangled net in the Pacific Ocean” @sea.marshall

Little is known about neuston, especially those found far from land in the heart of ocean gyres. “They are very difficult to study because they occur in the open ocean and you cannot collect them unless you go on marine expeditions, which cost a lot of money,” said Lanna Cheng, a research scientist at the University of California, San Diego. Because so little is known about the life history and ecology of these creatures, this study, though severely limited in size and scope, offers valuable insights to scientists.

“Lecomte finds a plastic crate surrounded by fish” @osleston

But Dr. Helm said there is another implication of the study: Organizations working to remove plastic waste from the patch may also need to consider what the study means for their efforts. There are several nonprofit organizations working to remove floating plastic from the Great Pacific Patch.

The largest, the Ocean Cleanup Foundation in the Netherlands, developed a net specifically to collect and concentrate marine debris as it is pulled across the sea’s surface by winds and currents. Once the net is full, a ship takes its contents to land for proper disposal. Dr. Helm and other scientists warn that such nets threaten sea life, including neuston.

Although adjustments to the net’s design have been made to reduce bycatch, Dr. Helm believes any large-scale removal of plastic from the patch could pose a threat to its neuston inhabitants. “When it comes to figuring out what to do about the plastic that’s already in the ocean, I think we need to be really careful,” she said. The results of her study “really emphasize the need to study the open ocean before we try to manipulate it, modify it, clean it up or extract minerals from it.”

“the crew often finds thousands of pieces of plastic daily in the water samples”

Laurent Lebreton, an oceanographer with the Ocean Cleanup Foundation, disagreed with Dr. Helm. “It’s too early to reach any conclusions on how we should react to that study,” he said. “You have to take into account the effects of plastic pollution on other species. We are collecting several tons of plastic every week with our system — plastic that is affecting the environment.” Plastic in the ocean poses a threat to marine life, killing more than a million seabirds every year, as well as more than 100,000 marine mammals, according to UNESCO. Everything from fish to whales can become entangled, and animals often mistake it for food and end up starving to death with stomachs full of plastic.

Ocean plastics that don’t end up asphyxiating an albatross or entangling an elephant seal eventually break down into microplastics, which penetrate every branch of the food web and are nearly impossible to remove from the environment. One thing everyone agrees on is that we need to stop the flow of plastic into the ocean. “We need to turn off the tap,” Mr. Lecomte said.”

“Glaucus, known as the blue sea dragon” – photos by Denis Riek

Sea Creatures Rafting in the Great Pacific Garbage Patch
by Jennifer Walter  /  May 4, 2023

“The Great Pacific Garbage Patch isn’t an impassable, solid mass in the middle of the ocean, but rather a lively, swirling soup of discarded trash and microplastics that churn with the currents. It’s the product of our unwanted wares sucked into a gyre — a powerful, circulating system of ocean currents. It might be tempting to think of this region of the Pacific as completely devoid of life, but recent studies show that sea creatures still find a way to thrive among the trash. Writing this week in the journal PLOS Biology, researchers report an abundance of surface-dwelling creatures called neustons living in the Great Pacific Garbage Patch.

Portugese man o’ war Physalia 

The same gyres that cause garbage patches to collect may also play a vital role in transporting neustons, which are critical to the food web, across the seas. While this means they’re likely to be found in garbage patches, it’s still not clear how human pollution will change their way of life. Back in 2019, French swimmer Ben Lecomte swam hundreds of miles through the Great Pacific Garbage Patch. During the expedition, a team of scientists collected samples from the boat that accompanied Lecomte to see what, if anything, was living there.

blue button jellyfish Porpita

It didn’t take long into the swim for Lecomte and the accompanying researchers to see creatures of all shapes and sizes float by. They spotted plenty of neustons like the violet sea snail Janthina and the blue button jelly Porpita in the garbage patch. And even larger animals like a sperm whale swam by, too, according to a 2019 report by ViceAmidst pollution, the ecosystem was finding a way to thrive, thanks to the vital nutrients that neustons provide to many ocean creatures. For the new study, the researchers broke down which neustons were most common in the Great Pacific Garbage Patch, based on data collected during Lecomte’s swim.

“bubble raft keeps a violet sea snail Janthina afloat at the surface”

Five types of neustons were recorded in the study: Janthina, Porpita, the sea raft Velella, the Portuguese man o’ war Physalia, and the blue sea dragon Glaucus. Every type was even more plentiful inside the Great Pacific Garbage Patch than outside of it. This showcases how the powerful gyres shape where they live, just as they cause garbage to collect in the same areas. While no evidence has been found that neustons can consume plastic, correlations between high plastic concentration and three types of neustons show that they may interact with the garbage patch in ways we don’t know about yet.

“A buoy barnacle, Dosima fascicularis, with aboral white float at the water’s surface.”

Other sea creatures like the rafting barnacle have been shown to consume microplastics regularly, though the health effects on these animals are unknown. Knowing where neustons live can give insight into the health of the entire ecosystem. But the researchers caution that much more data is needed to understand the full extent of neuston populations in ocean gyres, and how plastic accumulation affects them.

blue button jelly Velella – photos by Denis Riek

What is clear from the new research is that the Great Pacific Garbage Patch is more than a famous accumulation of trash — it’s also home to many creatures. “The ‘garbage patch’ is more than just a garbage patch. It is an ecosystem, not because of the plastic, but in spite of it,” said study author and marine biologist Rebecca Helm in a statement.”




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