Effect of carbon and nitrogen availability on intracellular amino acids and ammonium pools in the green alga Monoraphidium braunii

In this paper, we present results of our studies on nitrogen metabolism in the green alga Monoraphidium braunii, strain 202-7d, concerning changes in intracellular ammonium, glutamate and glutamine pools (as determined by rev ersed phase chromatography). We found that blocking of nitrogen assimilatio n at the GS or GOGAT steps quickly induced changes in intracellular amino a cid levels, which were opposite in the case of Gln. Monoraphidium cultures can recover from the effect of such inhibit ors, probably by its metaboliza tion. Darkness or addition of DCMU affected GS regulation in the same way i n Monoraphidium, but they provoked distinct effects on intracellular pools of amino acids. The inhibition of GS activity had a similar effect on the l evels of primary products of ammonium assimilation (Glu and Gln) regardless of the energetic state of cells.