ISSN:
1432-072X
Keywords:
Xanthobacter
;
Nitrogen fixation
;
Oxygen sensitivity
;
Nitrogen metabolism
;
Glutamine synthetase
;
Glutamate synthase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract N2-fixation was investigated in the chemoautotrophic hydrogen bacterium Xanthobacter H4-14. N2-fixing batch cultures of this organism could only be grown at pO2 values of around 0.02 bar, and in continuous culture dissolved oxygen tensions above 16 μM were found to inhibit N2-fixation. Xanthobacter H4-14 utilized a variety of amino acids, nitrate and ammonia as nitrogen sources. Cell-free extracts from steady-state continuous cultures of ammonia grown, nitrate grown and N2-fixing Xanthobacter were assayed for the presence of ammonia assimilation enzymes. No alanine dehydrogenase or glutamate dehydrogenase activity was detected. Ammonia was assimilated exclusively via the glutamine synthetase/glutamate synthase pathway, irrespective of the extracellular concentration of ammonia.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00409848
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