The Methylococcaceae are a family of bacteria that obtain their carbon and energy from methane, called methanotrophs.

The Methylococcaceae have internal membranes in the form of flattened discs, perpendicular to the cell wall.

[1] Methane is oxidized to give formaldehyde, which is fixed by a process called the ribulose monophosphate (RuMP) cycle.

[1] Catabolism does not involve a complete citric acid cycle.

[2] Some species of the Methylococcaceae have formed with certain marine mussels endosymbiotic relationships.