Methanotrophs are Gram-negative bacteria that utilize methane, a potent green house gas, as a sole carbon and energy source. These bacteria oxidise methane through a unique enzyme system known as methane monooxygenase (MMO), thus reducing of the amount of methane released to the Earth’s atmosphere. In methanotrophs, there are two types of MMO; a membrane bound particulate enzyme (pMMO) and a soluble cytoplasmic enzyme (sMMO). The expression of both enzymes is significantly affected by the availability of copper. Under high copper-biomass ratio, the biosynthesis of pMMO is switched on while sMMO is upregulated during growth at low copper-to biomass ratio. The exact role of copper in regulation of MMO in Mc. capsulatus is still unclear. We are studying the regulation of methane oxidation in methanotrophs using a combination of post-genomic techniques such as proteomics and transcriptomics and analysing mutants that are defective in copper homeostasis. In collaboration with colleagues in the USA and France we are also studying methanobaction, its biosynthesis and regulation.