Microbes are amazing chemists, performing reactions to recycle biological matter, depolluting environments, and contributing to Earth´s biogeochemical cycles. Among them are anaerobic methanotrophs, microbes that consume methane in oxygen-free environments. By preventing the release of this potent greenhouse gas into the atmosphere, they play an important role in mitigating climate change. However, studying the chemical reactions that these microbes carry out is challenging : They cannot be isolated and only thrive in complex microbial communities. Two teams from the IBS (led by Tristan Wagner and Antoine Royant), together with scientists from the Netherlands and Germany, have now unexpectedly discovered and characterized a new type of protein that encapsulates iron from these microbial consortia.
The scientists directly used a microbial community from a bioreactor to isolate a protein with an intense pink color and crystallized it without oxygen to determine its three-dimensional structure. They found that the protein is a cage, looking like the protein used in our body to store iron, but with a particularity : it contains a heme, a trait typical of bacterioferritin. Unlike traditional bacterioferritins, which assemble into structures of 24 protein copies, this newly discovered protein forms a compact cage of just 12 copies, creating an entirely novel assembly that could be useful for encapsulating other molecules for drug delivery. The authors named this protein “mini-bacterioferritin” due to its small size. Genomic analysis revealed that mini-bacterioferritins are not unique to methanotrophs. They are widespread among microbes but have been overlooked until now. This discovery, published in Communications Biology, serves as a reminder of the vast, unexplored potential hidden within microbial communities—and the importance of continuing to mine these biological treasures for scientific and industrial innovation.
Reference : Mini-bacterioferritins : structural insight into a ferritin-like protein from the anaerobic methane-oxidising archaeon Candidatus Methanoperedens carboxydivorans. Martijn Wissink, Sylvain Engilberge, Pedro Leão, Robert S. Jansen, Mike S.M. Jetten, Mélissa Belhamri, Olivier N. Lemaire, Antoine Royant, Cornelia U. Welte, and Tristan Wagner. Communications biology (2026) https://doi.org/10.1038/s42003-026-09796-4
bioRxiv preprint DOI : https://doi.org/10.1101/2025.06.06.658376
Contact : Tristan Wagner, Groupe Extremophiles et grands assemblages moléculaires (IBS/ELMA)
Participating institutions :
- Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, 28359, Bremen, Germany
- Department of Microbiology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Nijmegen, the Netherlands
- Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale, 38000, Grenoble, France
- European Synchrotron Radiation Facility, Grenoble, France