Explore a new Thematic Issue on C1 Metabolism from FEMS Microbiology Letters. One-carbon or “C1” metabolism has been studied for many years and in several different forms. This Thematic Issue brings together new research and covers several different subtopics. This issue includes studies on aerobic microorganisms in marine environments, methylotrophic methanogens, hydrogenotrophic methanogens, hemerythrins, methane in forest soils, and methanogenic archaea in peatlands.