TABLE 2.

MPN estimates for aerobic conditions^a

Bacterial group	MPN (± SE) for:
	1% O2, 1 mM acetate	1% O2, 30 mM acetate	20% O2, 30 mM acetate
Heterotrophs	3 × 105 ± 6 × 104	106 ± 2 × 105	109 ± 2 × 108
Methanotrophs	107 ± 3 × 106	3 × 106 ± 2 × 106	107 ± 7 × 106
NH4+ oxidizers	103 ± 3 × 102	<102	3 × 105 ± 6 × 104
S2O32− oxidizers	3 × 105 ± 6 × 104	105 ± 2 × 104	106 ± 2 × 105
Fe2+ oxidizers	<102	<102	<102

^aValues are for numbers of bacteria per gram dry weight of soil after stabilization of the number or at most after 10 weeks of incubation at 30°C.