NITROGEN DEPRIVATION OF ANABAENA SP STRAIN PCC-7120 ELICITS RAPID ACTIVATION OF A GENE-CLUSTER THAT IS ESSENTIAL FOR UPTAKE AND UTILIZATIONOF NITRATE

A transposon bearing luxAB, encoding luciferase, as a reporter of tran scription was used to identify genes that are activated rapidly upon d eprivation of Anabaena sp. strain PCC 7120 of fixed nitrogen, The thre e transposon-marked loci that were identified as responding most rapid ly and strongly are closely linked and situated within nirA and nrtC a nd between nrtD and narB, genes whose products are responsible for upt ake and reduction of NO2- and NO3-. A strain bearing a transcriptional fusion of narB to luxAB was constructed, Luminescence catalyzed by Lu xAB was used to report on the expression of the interrupted genes, Whe ther these genes are regulated only coordinately is discussed.