Table 2. Thaumarchaeal growth, AOA clade affiliation and NH3 oxidation activity in nine enrichment cultures from moss tundra (Lon-mt2) and frost boil (Knu-fb) soils incubated at different temperatures.
| Incubation temperature | Original soil | 16S rRNA gene copies fold increase | NH4+ consumption (μℳ NH4+ d−1) | NO2− production (μℳ NO2− d−1) |
AOA clade (no. of sequences) |
|
|---|---|---|---|---|---|---|
| A | C | |||||
| 4 °C | Knu-fb | 2.8 | 1.07 | −0.10 | 17 (94%) | 1 (6%) |
| Lon-mt2 | 2.4 | 0.93 | −0.24 | 10 (53%) | 9 (47%) | |
| Lon-mt2 | 1.8 | −1.48 | −0.79 | NA | NA | |
| AM±SD | 2.3±0.5a | 0.17±1.43a | −0.38±0.36a | |||
| 20 °C | Knu-fb | 5.4 | 4.18 | 3.48 | 8 (42%) | 11 (58%) |
| Lon-mt2 | 3.0 | 4.02 | 3.48 | 3 (15%) | 17 (85%) | |
| Lon-mt2 | 3.3 | 3.75 | 3.02 | NA | NA | |
| AM±s.d. | 3.9±1.3a | 3.98±0.22b | 3.33±0.27b | |||
| 28 °C | Knu-fb | 4.5 | 1.49 | 1.58 | 19 (100%) | 0 (0%) |
| Lon-mt2 | 1.4 | 0.92 | 1.05 | NA | NA | |
| Lon-mt2 | 1.2 | 2.44 | 0.79 | NA | NA | |
| AM±s.d. | 2.4±1.9a | 1.62±0.77a | 1.14±0.40c | |||
Abbreviations: AM±SD, arithmetic mean±s.d.; NA, not available.
Thaumarchaeal 16S rRNA gene copy increase was determined between days 26 and 40, and NH4+ consumption and NO2− production rates were determined between days 20 and 40. Proportion of sequences affiliated with the two AOA clades detected (A and C) are expressed as percentage in each clone library. Lowercase letters indicate significant differences between temperatures: 16S rRNA gene copies increase, P=0.3297; NH4+ consumption, P<0.01; NO2− production, P<0.0001.