Table 1.

Some characteristics of AAOB (nitrifying bacteria), methanotrophic bacteria, and unknown high-affinity methane oxidizers in soila

BacteriaPhylogenetic affiliationMembrane typeMajor fatty acidsbKey enzymeApparent Km for CH4 (μM)cVmax for CH4 (mmol · g of cells−1· h−1)Oxidation inhibited by C2H2, C2H4, DME, and COdGrowth inhibited by elevated NH3 concnCH4 required to maintain activity% Assimilation of oxidized CH4e
 Group 1γ-Proteobacteria Stacked, central14:0, 16:0, and 16:1 speciespMMO (+ some sMMO)0.8–3210–31+++29–62
 Group 2α-Proteobacteria Flat, peripheral18:1 speciespMMO (+ some sMMO)0.8–3210–31+++29–62
 Soil high affinity??18:1 species?0.01–0.06?+++20–54
 Group 3β-Proteobacteria Flat, peripheral16:0 and 16:1 speciesAMO2,000  0.03–0.59+0–17
 Group 4γ-Proteobacteria Stacked, central16:0 and 16:1 speciesAMO    6.60.01–0.08+1–47
  • a Data from references 1, 2, 5,9, 12, 17, 19, 20, 22, 28, 30, 31, 39, and40.

  • b A major fatty acid is present at a concentration of >10% in at least one member of each group.

  • c The values for nitrifiers were based on theKi of CH4 for ammonia oxidation.

  • d DME, dimethyl ether.

  • e The fate of labelled methane in nitrifiers is not known. The apparent assimilation could be due to nonspecific labelling by formaldehyde or assimilation at the level of CO2.