Further Studies on the Induction of Nitrate Reductase by Arginine in the Filamentous Cyanobacterium Oscillatoria chalybea

In an earlier publication we reported on the role o f arginine for the development o f nitrate reductase activity in cells o f the filamentous cyanobacterium Oscillatoria chalybea (Bednarz and Schmid, Z. Naturforsch. 46c, 591 (1991)). In the present paper we present further evidence that arginine is the natural inducer for nitrate reductase activity. Thus, we show that the induc­ tion is regulated by transcription, probably related to the apoprotein or the molybdenumcofactor. We also examined the influence o f arginine on nitrate reductase activity in the fila­ mentous cyanobacterium Anabaena PCC7120. In contrast to Oscillatoria chalybea this cyano­ bacterium forms heterocysts and shows nitrogen fixation activity. Like in Oscillatoria chalybea nitrate reductase activity in Anabaena PCC7120 is stimulated in the presence o f arginine as the sole nitrogen source. However, this stimulation is limited to an early growth stage. Sub­ sequently, nitrogen fixation activity appears and nitrate reductase activity decreases.