Glutamine synthetase and GlnR regulate nitrogen metabolism in WLY78.

WLY78, a N-fixing bacterium, has great potential use as a biofertilizer in agriculture. Recently, we have revealed that GlnR positively and negatively regulates the transcription of the (trogen ixation) operon () in WLY78 by binding to two loci of the promoter according to nitrogen availability. However, the regulatory mechanisms of nitrogen metabolism mediated by GlnR in the genus remain unclear.

Alanine synthesized by alanine dehydrogenase enables ammonium-tolerant nitrogen fixation in T27.

Most diazotrophs fix nitrogen only under nitrogen-limiting conditions, for example, in the presence of relatively low concentrations of NH (0 to 2 mM). However, T27 exhibits an unusual pattern of nitrogen regulation of nitrogen fixation, since although nitrogenase activities are high under nitrogen-limiting conditions (0 to 3 mM NH) and are repressed under conditions of nitrogen sufficiency (4 to 30 mM NH), nitrogenase activity is reestablished when very high levels of NH (30 to 300 mM) are present in the medium. To further understand this pattern of nitrogen fixation regulation, we carried out transcriptome analyses of T27 in response to increasing ammonium concentrations.