TABLE 2.

Structure of the methanotrophic-heterotrophic community enriched under different methane and oxygen concentrations at 30°C^a

Initial headspace concn (%)		Compositionb (%)
CH4	O2	Met 1	Het 1	Het 2	Het 3	Het 4	Het 5
4.5	19.0	50–60	45–55	1–5	1–5	35–45
8.7	18.5	60–65	55–65	1–5	1–5	30–40
19.4	15.5	65–85	50–60	1–5	1–5	25–35	1–5
20.2c	14.8	80–90	45–55	1–5	1–5	35–45	5–10

^aSimilar results were obtained at 20°C; only the relative proportions of the dominant heterotrophic populations changed significantly (Het 4 increased to approximately 55 to 70% and Het 1 decreased to approximately 20 to 35%). 

^bExpressed as the proportion of the total population for the methanotroph (Met 1) and as the relative proportion of the heterotrophic population for individual heterotrophs (Het 1 through 5). At least three replicate plates with 100 to 150 colonies on NMS-agarose medium (for the methanotroph) or on nutrient agar (for heterotrophs) were evaluated. 

^cAfter the first injection, CH₄ (20 ml) and O₂ (10 ml) were repeatedly injected to maintain low O₂ (3 to 5%) and excess CH₄ (10 to 15%) concentrations.