Importance of methane-oxidizing bacteria in the methane budget as revealed by the use of a specific inhibitor

Abstract

METHANE is a greenhouse gas whose concentration in the atmosphere is increasing^1–3. Much of this methane is derived from the metabolism of methane-generating (methanogenic) bacteria^4,5 and over the past two decades much has been learned about the ecology of methanogens; specific inhibitors of methanogenesis, such as 2-bromoethanesulphonic acid, have proved useful in this regard⁶. In contrast, although much is known about the biochemistry of methane-oxidizing (methanotrophic) bacteria⁷, ecological investigations have been hampered by the lack of an analogous specific inhibitor⁶. Methanotrophs limit the flux of methane to the atmosphere from sediments^8,9 and consume atmospheric methane¹⁰, but the quantitative importance of methanotrophy in the global methane budget is not well known⁵. Methylfluoride (CH₃F) is known to inhibit oxygen consumption by Methylococcus capsu-latus¹¹, and to inhibit the oxidation of ¹⁴CH₄ to ¹⁴CO₂ by endosymbionts in mussel gill tissues¹². Here we report that methylfluoride (MF) inhibits the oxidation of methane by methane monooxy-genase, and by using methylfluoride in field investigations, we find that methanotrophic bacteria can consume more than 90% of the methane potentially available.