Formation of the nitrogen-fixing enzyme system inAzotobacter vinelandii
作者:
G. W. Strandberg,
P. W. Wilson,
期刊:
Canadian Journal of Microbiology
(NRC Available online 1968)
卷期:
Volume 14,
issue 1
页码: 25-31
ISSN:0008-4166
年代: 1968
DOI:10.1139/m68-005
出版商: NRC Research Press
数据来源: NRC
摘要:
The formation and activity of nitrogenase2inAzotobacter vinelandiiOP was examined using a cell-free assay system. A lag period of about 30 min occurred between the exhaustion of the combined nitrogen source and growth on N2. Cells grown on ammonium acetate or potassium nitrate had no detectable nitrogenase activity. Nitrogenase activity appeared in cells, grown under a flowing gas phase of 20% O2– 60% He, about 45 min after the exhaustion of ammonia. Nitrogenase formation was inhibited in a closed system with an atmosphere containing 40% O2but not by one containing 20% O2. Hydrogen did not inhibit enzyme formation. The question of whether N2is required for the formation of the enzyme could not be answered as this gas could not be completely eliminated from the growth system. Chloramphenicol prevented the formation of the enzyme and inhibited nitrogen fixation in whole cells, but had no effect on cell-free enzyme activity. A brief rise in turbidity which occurred during nitrogenase formation appeared to be due to a color change in the cells from reddish brown to dark brown. Spectrophotometric examination of extracts from ammonia- and N2-grown cells did not reveal any components responsible for this color difference, but this result may reflect only the presence of interfering substances in the crude extract.
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