An ultra-stable protein nanowire made by bacteria provides clues to combating climate change.
Rapid global warming poses a severe and immediate threat to life on Earth. Rising temperatures are caused in part by atmospheric methane, which is 30 times more potent than CO2 at trapping heat. Microbes produce half of this methane and as temperatures continue to rise, microbial growth is accelerated, leading to a higher production of greenhouse gases than can be absorbed by plants. This weakens the Earth’s ability to act as a carbon sink and contributes to a rise in global temperatures.
A potential solution to this vicious circle could be another kind of microbe that eats up to 80% of methane flux from ocean sediments that protect the Earth. How microbes serve as both the biggest producers as well as consumers of methane has remained a mystery because they are very difficult to study in the laboratory. In the journal Nature Microbiology, surprising wire-like properties of a protein highly similar to the protein used by methane-eating microbes are reported by a Yale University team led by Yangqi Gu, and Nikhil Malvankar, of Molecular Biophysics and Biochemistry at Microbial Sciences Institute.
The team had previously shown that this protein nanowire shows the highest conductivity known to date, allowing the generation of the highest electric power by any bacteria. But to date, no one had discovered how bacteria make them and why they show such extremely high conductivity.
Using cryo-electron microscopy, Yangqi and the team were able to see the nanowire’s atomic structure and discover that hemes packed closely to move electrons very fast with ultra-high stability. It also explains how these bacteria can survive without oxygen-like membrane-ingestible molecules and form communities that can send electrons over 100 times bacterial size. Yangqi and the team also built nanowires synthetically to explain how bacteria make nanowires on demand.
“We are using these heme wires to generate electricity and to combat climate change by understanding how methane-eating microbes use similar heme wires,” Malvankar said.
Reference: “Structure of Geobacter cytochrome OmcZ identifies mechanism of nanowire assembly and conductivity” by Yangqi Gu, Matthew J. Guberman-Pfeffer, Vishok Srikanth, Cong Shen, Fabian Giska, Kallol Gupta, Yuri Londer, Fadel A. Samatey, Victor S. Batista and Nikhil S. Malvankar, 2 February 2023, Nature Microbiology.
Other authors are Malvankar Lab Members Matthew Guberman-Pfeffer, Vishok Srikanth, Cong Shen, Yuri Londer, Fadel Samatey with collaborators Prof. Victor Batista, Prof. Kallol Gupta, and Fabian Giska.