CHARACTERIZATION OF A PARACOCCUS-DENITRIFICANS MUTANT PLEIOTROPICALLYIMPAIRED IN NITROGEN-METABOLISM

A Tn5 insertional prototrophic mutant of Paracoccus denitrificans (UBM 219) was generated which grew on high (>1 mM) but not low (<0.5 mM) am monium as sole nitrogen source. It did not utilize nitrate and most am ino acids except glutamate and aspartate. UBM219 showed more than 10-f old lower levels of ammonium (methylammonium) transport, aspartate and alanine aminotransferase, but more than 10-fold higher activities of glutamate dehydrogenase and glutamate synthase. This pleiotropy indica tes a mutation in a regulatory gene affecting nitrogen metabolism in g eneral. - Ammonia assimilation pathways and regulation in Paracoccus r esemble the patterns in enterobacteria with the exception, that alanin e is generated by amino transfer from glutamate to pyruvate.