Methylococcus is a genus of Gram-negative, aerobic bacteria that live in soil, mud, and water and can use methane as their sole source of carbon and energy. The best-known species, Methylococcus capsulatus, is grown industrially to produce single-cell protein: a dried bacterial biomass rich in protein and B vitamins used in animal and aquaculture feeds. Because the process converts natural gas into feed protein, it is studied as a sustainable alternative to fishmeal and soy in livestock rations, reducing pressure on wild fisheries and farmland. Food-safety assessment of such novel proteins covers amino acid profile, nucleic acid content, and the absence of toxins before approval for feed use.