ISSN:
1432-072X
Keywords:
Nitrogen fixation
;
NH 4 + excretion
;
Photosynthesis
;
Rhodospirillum rubrum
;
Photosynthetic bacteria
;
Enzymes of ammonia assimilation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract NH 4 + excretion was undetectable in N2-fixing cultures ofRhodospirillum rubrum (S-1) and nitrogenase activity in these cultures was repressed by the addition of 10 mM NH 4 + to the medium. The glutamate analog,l-methionine-dl-sulfoximine (MSX), derepressed N2 fixation even in the presence of 10 mM extracellular NH 4 + . When 10 mg MSX/ml was added to cultures just prior to nitrogenase induction they developed nitrogenase activity (20% of the control activities) and excreted most of their fixed N2 as NH 4 + . Nitrogenase activities and NH 4 + production from fixed N2 were increased considerably when a combined nitrogen source, NH 4 + (〉40 μmoles NH 4 + /mg cell protein in 6 days) orl-glutamate (〉60 μmoles NH 4 + /mg cell protein in 6 days) was added to the cultures together with MSX. Biochemical analysis revealed thatR. rubrum produced glutamine synthetase and glutamate synthase (NADP-dependent) but no detectable NADP-dependent glutamate dehydrogenase. The specific activity of glutamine synthetase was observed to be maximal when nitrogenase activity was also maximal. Nitrogenase and glutamine synthetase activities were repressed by NH 4 + as well as by glutamate. The results demonstrate that utilization of solar energy to photoproduce large quantities of NH 4 + from N2 is possible with photosynthetic bacteria by interfering with their regulatory control of N2 fixation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00690229
