Fig. 1.

Copy numbers of bacterial amoA genes across DNA cesium chloride density gradient fractions from each treatment. The labeled treatments (diamonds) and control treatments (triangles) are shown for each stream biofilm incubated at 3 temperatures for 6 weeks. Leutra South (100 μM NH₄Cl) and Ammerbach biofilm enrichments (1,000 μM NH₄Cl) are denoted as LS and AS, respectively. The designation AS-13°C-3W indicates that Ammerbach biofilm enrichments were incubated at 13°C for 3 weeks. There were no control treatments for all 3-week or for 6-week incubations of LS at 13°C. The horizontal and vertical arrows indicate the DNA fractions used for clone library construction of active AOB and nonactive AOB 16S rRNA gene sequences, respectively, in Table 3.