International audience The goal of this Special Issue will be to provide a broad overview of the recent breakthroughs and current questions in the dynamic field of microbial C1 metabolism, as a crucial component of the biogeochemical processes of the planet in the Anthropocene. Contributions will range from the molecular level of model systems, to the global scale of environmental ecosystems, biogeochemical cycles, and natural and engineered ecosystems. The Special Issue will present fundamental and applied research on microorganisms, both cultured and uncultured, that are able to use C1 compounds, and compounds lacking carbon–carbon bonds for growth, including, for example, autotrophs, methylotrophs, phototrophs, methanogens, and acetogens. Topics will cover the physiology, genetics, ecology, and evolution of the microbial C1 metabolism in emblematic environments and ecosystems, corresponding to processes of chemical and light energy conversion, key enzymes of microbial C1 metabolism, and biotechnological applications in the context of the ongoing massive global change.