Arctic peatlands store vast amounts of carbon. As global temperatures increase and environments change in response, the stability of the carbon stored in these habitats has emerged as a pressing concern. Researchers delved deep into the soil microbiome, scrutinizing the functions of thousands of microorganisms in an Arctic peatland ecosystem. Contrary to previous assumptions, the study revealed that many microorganisms metabolize polyphenols. Scientists had believed that this complex class of carbon compounds was inert and an important part of carbon storage. Armed with this new insight, scientists are better equipped to forecast the impacts of climate change on Arctic ecosystems and devise targeted strategies for mitigating these effects.

Peatlands have long intrigued scientists as reservoirs of terrestrial carbon, yet the role of microorganisms in carbon cycling has remained enigmatic. Contrary to past assumptions, this new research challenges the notion that peatland microorganisms exclusively degrade polyphenols under oxygenated conditions using phenol oxidase. Drawing from insights derived from other oxygen-limited environments like the human gut and rumen, where alternative enzymes and pathways metabolize polyphenols, the research team developed a novel computational tool to rapidly profile polyphenol metabolisms in microbial genomes. This software, applied to thousands of microbial genomes sampled from an Arctic peatland, unveiled a surprising diversity of polyphenol-transforming biochemical pathways. Remarkably, certain microorganisms encoded a profusion of these genes, signifying a polyphenol degradation prowess. Furthermore, the findings highlight the adaptability of microbial gene expression to shifts in soil redox conditions across the landscape.

By uncovering this hidden biochemistry, this research pioneers a new understanding of carbon cycling in these climate critical ecosystems. These insights not only expand knowledge of microbial metabolism but also underscore the intricate interplay between microorganisms and carbon dynamics in the face of climate change.

This material was based on work supported by the Department of Energy (DOE) Office of Science, Biological and Environmental Research Program, as well as the National Sciences Foundation Biological Integration Institute. A portion of this research was performed under the DOE Facilities Integrating Collaborations for User Science program and used resources at the Joint Genome Institute and the Environmental Molecular Sciences Laboratory, both DOE Office of Science user facilities.

The microorganisms belong to the genus Acetobacterium and they are commonly found in wastewater environments throughout the world.

Forever chemicals, also known as per- and polyfluoroalkyl substances or PFAS, are so named because they have stubbornly strong carbon-fluorine chemical bonds, which make them persistent in the environment.

The microorganisms discovered by UCR scientists and their collaborators can cleave those stubborn fluorine-to-carbon bonds, they reported Wednesday, July 17, in the journal Science Advances.

“This is the first discovery of a bacterium that can do reductive defluorination of PFAS structures,” said Yujie Men, corresponding author of the study and an associate professor at UCR’s Bourns College of Engineering in the Department of Chemical and Environmental Engineering.

Men cautioned that the bacteria were effective only on unsaturated PFAS compounds, which have double carbon-to-carbon bonds in their chemical structures.

But importantly, the scientists also identified the specific enzymes in these bacteria essential for cleaving the carbon-fluorine bonds. This discovery opens the door for bioengineers to improve these enzymes so they can be effective on other PFAS compounds. (Enzymes are proteins that act as catalysts for biochemical reactions.)

“If we can understand the mechanism, maybe we can find similar enzymes based on the identified molecular traits and screen out more effective ones,” Men said. “Also, if we can design some new enzyme or alter this known enzyme based on the mechanistic understanding, we could be able to make it more efficient and work with a broader range of PFAS molecules .”

Last year, Men published a paper that identified other microorganisms that cleave the carbon-chlorine bond in chlorinated PFAS compounds, which triggers substantial spontaneous defluorination and destroys this group of pollutants. The most recent discovery greatly expands the number of PFAS compounds that can be destroyed biologically. Using bacteria to treat groundwater is cost effective because the microorganisms destroy pollutants before the water reaches wells. The process involves injecting the groundwater with the preferred bacteria species along with nutrients to increase their numbers.

Because PFAS compounds are linked to cancer and other human health maladies, the U.S. Environmental Protection Agency, or EPA, imposed water-quality limits earlier this year that restrict certain forever chemicals to only four parts per trillion in the nation’s tap water, spurring water providers to find PFAS cleanup solutions.

PFAS compounds came into widespread use in thousands of consumer products starting in the 1940s because of their ability to resist heat, water, and lipids. Examples of PFAS-containing products include fire suppressant foams, grease-resistant paper wrappers and containers such as microwave popcorn bags, pizza boxes, and candy wrappers; also, stain and water repellents used on carpets, upholstery, clothing, and other fabrics; according to the EPA.

The paper’s title is “Electron-bifurcation and fluoride efflux systems in Acetobacterium spp. Drive defluorination of perfluorinated unsaturated carboxylic acids.” Yaochun Yu is the lead author. He was a visiting student scientist and a UCR post-doctoral scientist at UCR before joining the Swiss Federal Institute of Aquatic Science and Technology, or Eawag, in 2022.

In addition to Yu and Men, the co-authors authors are Fengjun Xu, Weiyang Zhao, Calvin Thoma, Shun Che, Jack E. Richman, Bosen Jin, Yiwen Zhu, Yue Xing, and Lawrence Wackett.

Using satellite measurements of cloud cover and the solar radiation reflected by sea ice between 1980 and 2023, the researchers found that the percent decrease in sea ice’s cooling power is about twice as high as the percent decrease in annual average sea ice area in both the Arctic and Antarctic. The added warming impact from this change to sea ice cooling power is toward the higher end of climate model estimates.

“When we use climate simulations to quantify how melting sea ice affects climate, we typically simulate a full century before we have an answer,” said Mark Flanner, professor of climate and space sciences and engineering and the corresponding author of the study published in Geophysical Research Letters.

“We’re now reaching the point where we have a long enough record of satellite data to estimate the sea ice climate feedback with measurements.”

The Arctic has seen the largest and most steady declines in sea ice cooling power since 1980, but until recently, the south pole had appeared more resilient to the changing climate. Its sea ice cover had remained relatively stable from 2007 into the 2010s, and the cooling power of the Antarctic’s sea ice was actually trending up at that time.

That view abruptly changed in 2016, when an area larger than Texas melted on one of the continent’s largest ice shelves.The Antarctic lost sea ice then too, and its cooling power hasn’t recovered, according to the new study. As a result, 2016 and the following seven years have had the weakest global sea ice cooling effect since the early 1980s.

Beyond disappearing ice cover, the remaining ice is also growing less reflective as warming temperatures and increased rainfall create thinner, wetter ice and more melt ponds that reflect less solar radiation. This effect has been most pronounced in the Arctic, where sea ice has become less reflective in the sunniest parts of the year, and the new study raises the possibility that it could be an important factor in the Antarctic, too — in addition to lost sea ice cover.

“The changes to Antarctic sea ice since 2016 boost the warming feedback from sea ice loss by 40%. By not accounting for this change in the radiative effect of sea ice in Antarctica, we could be missing a considerable part of the total global energy absorption,” said Alisher Duspayev, doctoral student in physics and the study’s first author.

The research team hopes to provide their updated estimates of sea ice’s cooling power and climate feedback from less reflective ice to the climate science community via a website that is updated whenever new satellite data is available.

“Climate change adaptation plans should bring aboard these new numbers as part of the overall calculus on how rapidly and how widely the impacts of cryospheric radiative cooling loss will manifest on the global climate system,” said Aku Riihelä, research professor at the Finnish Meteorological Institute and co-author of the study.

The research was funded by the University of Michigan Rackham Graduate School and the Research Council of Finland.

Mark Flanner is also a professor of earth and environmental sciences at the College of Literature, Science, and the Arts.