Monomeric NarB is a dual-affinity nitrate reductase, and its activity is regulated differently from that of nitrate uptake in the unicellular diazotrophic cyanobacterium Synechococcus sp. strain RF-1.

ABSTRACT: Synechococcus sp. strain RF-1 is a unicellular freshwater cyanobacterium that fixes N(2) aerobically and exhibits a circadian rhythm for nitrogenase activity under a light-dark regimen. Synechococcus sp. strain RF-1 also utilizes nitrate, nitrite, or ammonium for growth. Under the diazotrophic growth, the nitrate uptake in Synechococcus sp. strain RF-1 was induced by nitrate or nitrite but repressed by ammonium. In contrast, a prominent nitrate reductase (NR) activity was detected in diazotrophically grown cells using the reduced methyl viologen assay. The NR activity was not inhibited by ammonium and only slightly enhanced by nitrate. The different expression patterns of nitrate uptake and NR in Synechococcus sp. strain RF-1 were reflected in general at the transcript level determined by

SUBMITTER: Wang TH 

PROVIDER: S-EPMC193977 | biostudies-literature | 2003 Oct

REPOSITORIES: biostudies-literature