Nitrogen nutrition in the cyanobacterium Nostoc ANTH, a symbiotic isolate from Anthoceros: uptake and assimilation of inorganic-n and amino acids.
Amino acid uptake and utilization of various nitrogen sources (amino acids, nitrite, nitrate and ammonia) were studied in Nostoc ANTH and i ts mu tant (Het(-)Nif(-)) isolate defective in heterocyst formation and N2-fixation. Both parent and its mutant grew at the expense of glutamine, asparagine and arginine as a source of fixed-nitrogen. Growth was better in glutamine-and asparagine-media as compared to that in arginine media. Glutamine and asparagine repressed heterocyst formation, N2-fixation and nitrate reduction in Nostoc ANTH, but arginine did so only partially. The poor growth in arginine-medium was not due to poor uptake rates, since the uptake rates were not significantly different from those for glutamine or asparagine. The glutamine synthetase activity remained unaffected during cultivation in media containing any one of the three amino acids tested. The uptake of amino acids was substrate-inducible, energy-dependent and required de novo protein synthesis. Nitrate and ammonium repressed ammonium uptake, but did not repress uptake of amino acids. In N2-medium (BG-11(0)), the uptake of ammonium and amino acids in the mutant was significantly higher than its parent strain. This was apparently due to nitrogen limitation since the mutant was unable to fix N2 and the growth medium lacked combined-N.
Biochemistry Department, North-Eastern Hill University, Shilong 793 022, India.
Jyotirmoy
J
Bhattacharya
Arvind Kumar
AK
Singh
Amar Nath
AN
Rai
D000596:Amino Acids / Q000737:chemistry*; D049936:Anthocerotophyta / Q000378:metabolism*; D001120:Arginine / Q000737:chemistry; D001216:Asparagine / Q000737:chemistry; D003470:Culture Media / Q000737:chemistry; D000458:Cyanobacteria / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000737:chemistry / Q000378:metabolism; D005973:Glutamine / Q000737:chemistry; D007287:Inorganic Chemicals; D009154:Mutation; D050901:Nitrate Reductase / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry*; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry
D000596:Amino Acids; D003470:Culture Media; D007287:Inorganic Chemicals; D000644:Quaternary Ammonium Compounds; D005973:Glutamine; D001216:Asparagine; D001120:Arginine; D009591:Nitrogenase; D050901:Nitrate Reductase; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen