The rapid quantification and detection of nitrifying bacteria by using monoclonal antibody method

Monoclonal antibodies against the two kinds of nitrifying bacteria Nitrosomonas europaea (IFO14298) and Nitrobacter winogradskyi (IFO14297) were raised and isotypes of these monoclonal antibodies, IgM and IgG₁, were successfully obtained. Cross reactivities of these monoclonal antibodies against various kinds of representative heterotrophic bacteria turned out to be relatively low by competitive ELISA. In contrast, these monoclonal antibodies were very specific for nitrifying bacteria used as antigens. By means of sandwich ELISA using different isotype monoclonal antibodies such as IgM and IgG₁, calibration curves were successfully developed for quantification of nitrifying bacteria. It was shown that the obtainable lower limit of quantification of N. europaea and N. winogradskyi were 7.0 × 10⁶ N/ml and were 6.0 × 10⁵ N/ml, respectively. Nitrifying bacteria in activated sludge of advanced domestic wastewater treatment johkaso were counted by sandwich ELISA and MPN methods. The bacterial number estimated by MPN method was lower than that estimated by sandwich ELISA. It was indicated that this monoclonal antibody method could be used as a quick and powerful tool for estimating and controlling the population of nitrifying bacteria in the advanced domestic wastewater treatment processes.