The methanogenic redox cofactor F₄₂₀ is widely synthesized by aerobic soil bacteria

F₄₂₀ is a low-potential redox cofactor that mediates the transformations of a wide range of complex organic compounds. Considered one of the rarest cofactors in biology, F₄₂₀ is best-known for its role in methanogenesis and has only been chemically identified in two phyla to date, the Euryarchaeota and Actinobacteria. In this work, we show that this cofactor is more widely distributed than previously reported. We detected the genes encoding all five known F₄₂₀ biosynthesis enzymes (cofC, cofD, cofE, cofG, and cofH) in at least 653 bacterial and 173 archaeal species, including members of the dominant soil phyla Proteobacteria, Chloroflexi, and Firmicutes. Metagenome datamining validated that these genes were disproportionately abundant in aerated soils compared to other ecosystems. We confirmed through HPLC that aerobically-grown stationary-phase cultures of the bacteria Paracoccus denitrificans, Oligotropha carboxidivorans, and Thermomicrobium roseum synthesized F₄₂₀, with oligoglutamate sidechains of different lengths. To understand the evolution of F₄₂₀ biosynthesis, we also analyzed the distribution, phylogeny, and genetic organization of the cof genes. Our data suggest that, while the F_o precursor to F₄₂₀ originated in methanogens, F₄₂₀ itself was first synthesized in an ancestral actinobacterium. F₄₂₀ biosynthesis genes were then disseminated horizontally to archaea and other bacteria. Together, our findings suggest the cofactor is more significant in aerobic bacterial metabolism and soil ecosystem composition than previously thought. The cofactor may confer several competitive advantages for aerobic soil bacteria by mediating their central metabolic processes and broadening the range of organic compounds they can synthesize, detoxify, and mineralize.