In this study, we evaluated the effect of signal molecules using recombinant nitrosomonas europaea. N.europaea is one of the major bacterias which are involeved in nitrification.This recombinant N.europaea is reporter assay system using the promoter of Hydroxylamine oxidoreductase (HAO). HAO is the one of the main enzymes in nitrification. So luminescence intensity and gene expression of HAO are closely related, this strain is usuful to assess the change of important gene expression which is difficult to see in a wild strain. We conducted the experiment that we added the many kinds of signal moleceles to this recombinant N.europaea and incubate to measure luminescence intensity and nitrification activity afterward. The systems which is added specific signal molecules, their luminescence intensities significantly increased and their nitrification activities also increased in specific condition. To our knowledge, there is no report that N.europaea senses the signal molecules and change their nitrification activites, so this results have novelty. From these results, now we build up a hypothesis that N.europaea senses signal molecules directly to activate nitrification in activated sludge too.
Fig.1 recombinant N.europaea
Fig.2 luminescence intensity
Fig. 3 residual ammonium concentration