Simultaneous Oxidation of Atmospheric Methane, Carbon Monoxide and Hydrogen for Bacterial Growth

Abstract

The second largest sink for atmospheric methane (CH₄) is atmospheric methane oxidizing-bacteria (atmMOB). How atmMOB are able to sustain life on the low CH₄ concentrations in air is unknown. Here, we show that during growth, with air as its only source for energy and carbon, the recently isolated atmospheric methane-oxidizer <i>Methylocapsa gorgona</i> MG08 (USCα) oxidizes three atmospheric energy sources: CH₄, carbon monoxide (CO), and hydrogen (H₂) to support growth. The cell-specific CH₄ oxidation rate of <i>M. gorgona</i> MG08 was estimated at ~0.7 × 10⁻¹⁸ mol cell⁻¹ h⁻¹, which, together with the oxidation of CO and H₂, supplies 0.38 kJ Cmol⁻¹ h⁻¹ during growth in air. This is seven times lower than previously assumed necessary to support bacterial maintenance. We conclude that atmospheric methane-oxidation is supported by a metabolic flexibility that enables the simultaneous harvest of CH₄, H₂ and CO from air, but the key characteristic of atmospheric CH₄ oxidizing bacteria might be very low energy requirements.