SALMONELLA-TYPHIMURIUM NIT IS NADE - DEFECTIVE NITROGEN-UTILIZATION AND AMMONIA-DEPENDENT NAD SYNTHETASE

S. typhimurium nit mutants are defective in nitrogen assimilation, des pite having normal levels of assimilatory enzymes. Complementation, en zyme assays, and genetic mapping show that nit is nadE. We present evi dence that ammonia, not glutamine, is the physiological substrate for eubacterial NAD synthetases and that low activity completely accounts for the mutant phenotype.