The response of methane consumption by pure cultures of methanotrophic bacteria to oxygen

The rates of CH4 oxidation by strains of groups I and II methanotrophs in pure culture were studied at various O-2 concentrations from 0 to 63% v/v. In the presence of nonlimiting dissolved CH4 and inorganic nitrogen, O-2 concentrations from 0.45 to 20% v/v supported maximum rates of CH4 oxidation. The critical dissolved O-2 concentration under our conditions was about 5.7 mu M, below which O-2 was limiting for CH4 oxidation. Concentrations of O-2 up to 63% v/v depressed the activity of CH4 oxidation by greater than or equal to 23%. We conclude that methanotrophs are not microaerophilic under the conditions of our experiments and that they have a high affinity for O-2.