TABLE 3.

Quantitative analyses of AOA and AOB by real-time PCR^a

Tank name	AOA			AOB			Ratio of AOA to AOB cells
	No. of copies (±SD) (103) ng−1 DNA	No. of cells (±SD) (106) g−1 of dry sand	% of AOA cells g−1 of sand (±SD)	No. of copies (±SD) (103) ng−1 DNA	No. of cells (±SD) (106) g−1 of dry sand	% of AOB cells g−1 of sand (±SD)
Coastal fish tank	3.0 (±0.10)	7.4 (±0.25)	3.9 (±0.13)	2.5 (±0.03)	2.5 (±0.02)	1.3 (±0.01)	3.0
Cold-water tank	2.8 (±0.06)	5.3 (±0.11)	2.8 (±0.06)	3.8 (±0.04)	2.9 (±0.03)	1.5 (±0.02)	1.8
Ocean sunfish tank	2.0 (±0.14)	6.8 (±0.46)	3.6 (±0.24)	2.2 (±0.17)	3.0 (±0.23)	1.6 (±0.12)	2.3

^aReal time PCR assays were carried out with the newly designed primers (Arch-amoA-79F and Arch-amoA-479R), which target clusters A1, A3, A4, and A5, as shown in Fig. 1A, but not cluster A2 and the soil/sediment cluster proposed by Beman et al. (1). AOA and AOB data are means ± standard deviations (SD) for n = 3. The numbers of cells g⁻¹ of dry sand assume a single amoA copy per AOA genome and 2.5 amoA copies per AOB genome (15). Percentages of AOA and AOB cell counts from aquarium biofiltration sand were derived from the total cell counts, assumed to be 1.9 × 10⁸ cells g⁻¹ of sand (22).