Newly Discovered Ammonia-Tolerant Bacterium Found to Convert High-Protein Waste into Methane: May Explain Why Some Anaerobic Digesters Stop When Others Don’t

     A new bacterium has been discovered that converts organic waste into methane. Typically, bacteria break organic waste down into simple compounds that then break down into organic acids such as acetic acid. These organic acids are then consumed by methanogenic bacteria, or methanogens, also known as anaerobic bacteria, because they do not consume oxygen, and are then converted into methane. Researchers at the University of British Columbia in Vancouver, Canada, led by Dr. Ryan Ziels, found that when there were no more methanogens left to consume acetic acid, their anaerobic digester was still making methane. In order to solve the mystery, they fed carbon to microbes to trace the carbon in proteins and found that a previously unknown bacterium was responsible for the continued methane conversion. These new microbes had one feature in particular, different from the other methanogens. They tolerate the high ammonia levels that are produced by protein-rich food, which shut down other methane producers. The discovery is not exactly game-changing, but it does improve our understanding and may have applicability in optimizing composting and possibly breaking down other materials like plastics. It also helps explain the mystery of why some aerobic digestors stop digesting when others continue digesting.

     The scientists were working at the City of Surrey Organic Waste and Biofuel facility, which has been operational since 2017, and which digests about 115,000 tons of food waste annually, to produce biomethane, also known as renewable natural gas.    

     The previously unknown bacterium is in the Natronincolaceae family. These syntrophic bacteria are hard to isolate and study. Thus, the methods used in the study – stable isotope probing and metaproteomics – have proven useful in the discovery of this:

“…rare and so-far uncharacterized syntrophic bacterium belonging to the family Natronincolaceae that expressed a previously hypothesized oxidative glycine pathway for syntrophic acetate oxidation.”

     According to the University of British Columbia:

“Protein-rich food waste naturally produces ammonia as it breaks down, but too much ammonia can halt methane production and cause acetic acid to build up, turning waste tanks acidic and unproductive. The newly discovered microbes, however, tolerate high ammonia levels that would shut down other methane producers, keeping the system running when it would normally fail.”

"Municipal facilities owe a lot to these organisms," said Dr. Ziels. "If acetic acid builds up, tanks have to be dumped and restarted—an expensive, messy process."

“The findings help explain why some digesters sputter while others, like Surrey's, continue producing energy under challenging conditions. The discovery also suggests that high-ammonia environments may actually benefit these key microbes, offering insights for more efficient designs.”

     The researchers are now utilizing similar techniques to study how microbes break down microplastics in the ocean. The current study marks an improvement in our overall understanding of anaerobic digestion.

     The study was published in Nature Microbiology. 

 

References:

 

Researchers discover previously unknown microbe capable of solving global crisis: 'We noticed something odd'. Brynne Wilcox. The Cool Down. October 24, 2025. Researchers discover previously unknown microbe capable of solving global crisis: 'We noticed something odd'

UBC researchers discover microbes turning food waste into energy. The University of British Columbia. Faculty of Applied Science. UBC Engineering. October 23, 2025. UBC researchers discover microbes turning food waste into energy - News | UBC Engineering

City of Surrey Organic Waste and Biofuel Facility. Convertus. Convertus City of Surrey Organic Waste and Biofuel Facility

Activity-targeted metaproteomics uncovers rare syntrophic bacteria central to anaerobic community metabolism. Skyler Friedline, Elizabeth A. McDaniel, Matthew Scarborough, Maxwell Madill, Kate Waring, Vivian S. Lin, Rex R. Malmstrom, Danielle Goudeau, William Chrisler, Morten K. D. Dueholm, Leo J. Gorham, Chathuri J. Kombala, Lydia H. Griggs, Heather M. Olson, Sophie B. Lehmann, Nathalie Munoz, Jesse Trejo, Nikola Tolic, Ljiljana Pasa-Tolic, Sarah M. Williams, Mary Lipton, Steven J. Hallam & Ryan M. Ziels. Nature Microbiology (October 21, 2025). Activity-targeted metaproteomics uncovers rare syntrophic bacteria central to anaerobic community metabolism | Nature Microbiology