Metals and Microbiology

Methane is oxidized under aerobic conditions by a group of bacteria called methanotrophs. These widespread bacteria play an important role in the global cycling of methane. Two types of methane oxidation systems are known, a ubiquitous particulate methane monooxygenase (pMMO) and a cytoplasmic soluble methane monooxygenase (sMMO) found in only a few strains. These enzymes have different catalytic characteristics, and so it is important to know the conditions under which each is expressed. In those strains containing both sMMO and pMMO, the available copper concentration controls which enzyme is expressed. However, the activity of the pMMO is also affected by copper. Data on methane oxidation in natural samples suggest that methanotrophs are not copper-limited in nature and express the pMMO predominantly.