FIG. 6.

P. stutzeri nirS copy number measured by real-time PCR without (black bars) and with (gray bars) the addition of 10⁶ P. stutzeri nirS copy numbers to DNA extracted from the following environmental samples: KBS, soil from KBS (Mich.); SCH, groundwater from Schoolcraft bioremediation site (Mich.); SHI, groundwater from Shiprock (N.Mex.); WIN, freshwater sediment from Wintergreen Lake (Mich.); WAS, marine sediment from Washington margin (Wash.); PUG, marine sediment from Puget Sound (Wash.).