TABLE 1.

K_m(app) values measured for methanotrophic bacteria, methanotrophic enrichment cultures, and soil^a

Sample (reference)	Km(app) (μM CH4)
	<1 μM	>1 μM
Literature
Methanotrophs, MMO (5, 18)		0.8–66
Aerobic interfaces of methanogenic soil (7, 39)		1.0–11
Aerobic upland soils (1, 3, 7, 8, 13)	0.010–0.280
Aerobic upland soils, enriched with 20% CH4 (1)	0.015–0.450	1.7–28
Organic soil (8)	0.060–0.280b
Organic soil, enriched with 10% CH4 (8a)		2.7–6.7
This study
Enrichment culture
Grown on <275 ppmv of CH4	0.056, 0.083, 0.173, 0.186
Transferred to 1,000 ppmv of CH4	0.330, 0.566
Transferred to 1% CH4		1.96, 2.60
Coculture; type II methanotroph LR1 + Variovorax sp.	0.129, 0.177, 0.183, 0.188

^aFor the literature, the range of reported values is shown. For experimental data, values from at least two trials (each with a separately grown culture) are shown. 

^bEstimated as 80 to 90 nM in the absence of NH₄⁺.