Abstract
An exploratory effort to selectively detect the presence of a nitrifying bacterium, Nitrosomonas europaea, successfully demonstrated the fundamental utility of an enzyme-based immunoassay protocol. The applied polyclonal antibody test seemingly offered a marked improvement over the available analytical options, including plating, activity, and fluorescence immunoassay techniques. Following an initial purification step to enhance overall specificity, this procedure had an apparent lower limit of detection of approximately 5 x 10 cells per ml. Tests conducted with activated sludge samples exhibited a distinct difference between nitrifying and nonnitrifying mixed liquors, although the highest Nitrosomonas levels observed (i.e., at 1 to 2% of the overall viable cell density) were relatively close to the latter detection boundary.
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