In sewage sludge and oxygen-free sediments around the world, a humble bacterium called Acetobacterium dehalogenans has been quietly performing a feat that remained mysterious to science until now: converting a toxic, ozone-depleting gas into harmless substances. A research team led by biologist Prof. Julia Kurth from the University of Münster has discovered and characterized the previously unknown enzyme system that makes this detoxification possible—a finding that could reshape how we understand both microbial life and the fate of one of the atmosphere's most troubling pollutants.
Chloromethane is a gas with a dual origin. Some of it comes from human activity: the combustion of coal, biomass, and other raw materials release it into the air. But nature produces it too. Algae, plants, and fungi naturally generate chloromethane as part of their metabolism. The problem is significant. This gas is toxic to humans and plays a measurable role in depleting the ozone layer—the same protective shield that safeguards us from ultraviolet radiation. Yet despite decades of research, scientists understood only part of the story of how it gets broken down.
Scientists already knew that certain aerobic bacteria—those requiring oxygen—could degrade chloromethane. They also knew that Acetobacterium dehalogenans, an anaerobic bacterium thriving in oxygen-free environments like sewage sludge, could use chloromethane as an energy and carbon source, thereby detoxifying it. What remained hidden was how the process actually worked in these anoxic conditions. Kurth's team, working across laboratories at the University of Strasbourg, the University of Grenoble, the University of Marburg, and the Max Planck Institute for Terrestrial Microbiology, has now filled that gap with findings published in Nature Communications.
The newly discovered enzyme system works by removing the chloride ion from the methyl group—a structure made of one carbon atom and three hydrogen atoms. Once separated, the methyl group becomes a carbon and energy source for the bacterium. But the mechanism is far more elegant than simple chemistry. The researchers discovered that chloromethane is guided through a unique molecular tunnel system to the enzyme's active center, where the methyl transfer occurs. This tunnel architecture differs fundamentally from other known methyl-transferring enzymes, revealing an entirely novel approach to breaking down this pollutant.
What makes this discovery even more consequential is its prevalence. The genetic instructions for these detoxifying proteins exist not just in sewage bacteria but across multiple microbial species—including some living in human gastrointestinal tracts and in deep seabed sediments. This widespread distribution suggests the chloromethane-degradation pathway is far more common in nature than anyone suspected.
The implications ripple across multiple fields. Environmental remediation could be transformed: anaerobic bacteria with this enzyme system can decompose chloromethane in soils and waters where oxygen is absent, tackling contamination in conditions where other remediation strategies fail. Climate science gains a crucial tool as well. By identifying these enzymes and genes, researchers can now predict which other anaerobic microbes convert chloromethane and where they live. This knowledge helps refine our understanding of how chloromethane cycles globally—essential for building better climate models and tracking ozone depletion. Even industry sees opportunity: the enzyme could selectively break down halogenated compounds in controlled chemical processes.
As Kurth notes in the paper, understanding how nature already handles chloromethane opens doors we've only recently realized existed.