Methane - a potent greenhouse gas - constantly seeps from the ocean floor and can rise into the atmosphere. Now, an international team led by scientists with the USC Dornsife College of Letters, Arts and Sciences has uncovered how tiny microorganisms work together as a living electrical network to consume some of this gas before it escapes, acting as a powerful living filter.
By revealing how these microbes naturally reduce methane emissions, the findings could lead to innovative strategies to better control methane release in both natural and engineered environments.
The study, published in the journal Science Advances, sheds light on a unique partnership between two very different microbes: anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB).
Alone, neither microbe can consume methane. When ANME break down methane, the process releases electrons that must be offloaded - a process known as a redox reaction, in which electrons move from one molecule to another - much like how humans rely on oxygen to accept electrons. Without an electron acceptor, methane consumption stalls.
This is where their bacterial partners step in.
While unable to consume methane themselves, the SRB help by accepting the electrons released during the process and transferring them to SRB's electron acceptor, sulfate, which powers their own metabolism.
"These two very different microbes come together into physically interconnected bundles," said Moh El-Naggar, Dean's Professor of Physics and Astronomy and professor of chemistry and biological sciences at USC Dornsife, and one of the study's lead researchers. "And the whole process works because conductive redox proteins link them up into functioning electrical circuits."
Using specialized electrochemical methods, the international research team - including scientists from Caltech, Peking University and the Max Planck Institute of Marine Microbiology - measured this electron exchange in the lab for the first time, using samples collected from different marine methane seeps, including the Mediterranean Sea, Guaymas Basin and the California coast.
"These microbial partnerships act as natural sentries, playing a crucial role in limiting the release of methane into the ocean and atmosphere," said Hang Yu, the study's lead author, who began this research nine years ago during his PhD at Caltech and focused on it as a postdoctoral fellow at USC Dornsife. Now an assistant professor at Peking University, Yu added, "By uncovering how these partnerships function, we gain insight into how life has evolved over billions of years, even in extreme environments, to consume potent greenhouse gases."
The researchers say the discovery offers new insight into how unseen microbial activity may influence Earth's systems in ways we're only beginning to understand.
"It may surprise people to know that microbes, even in the remotest of places, work together in sophisticated ways that influence processes on a planetary scale," said Victoria Orphan, James Irvine Professor of Environmental Science and Geobiology at Caltech and co-author of the study. "This discovery, the result of nearly a decade of multidisciplinary research, is a testament to persistence and collaboration in science. It underscores how much we still have to learn about the microbial ecosystems we depend on."
About the study
The research was conducted by an international team that also included Shuai Xu and Yamini Jangir, former USC and Caltech postdoctoral scholars, and Gunter Wegener, a senior scientist at the Max Planck Institute of Marine Microbiology. The study was funded by the U.S. Department of Energy, the Air Force Office of Scientific Research, the National Natural Science Foundation of China and Germany's Excellence Initiative.
