窒素固定能を有する水素細菌のnitrogenaseに及ぼす酸素の影響

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The growth rate of N2-fixing hydrogen bacteria strain N 34 remarkably decreased with increasing initial Po2 in case of N2-fixing chemolithoautotrophic growth. The growth suppression by O2 was, however, minimized when nitrogen compound was added to the culture media in advance as far as Po2 under 80 mmHg. Nitrogenase activity assayed by acetylene reductivity was detected in the cells grown with N2-fixation, but not in the cells grown in the media containing nitrogen compound such as urea. Nitrogenase activity was inhibited remarkably under high Po2. These results suggest that the growth suppression by O2 lower than 80 mmHg of Po2 in case of N2-fixing chemolithoautotrophic growth is mainly due to the inhibition of the nitrogenase activity. When the gas phase of the culture was replaced by that containing 90 mmHg of Po2 in the exponential phase of the growth which had started under 30 mmHg of Po2, nitrogenase was irreversibly inhibited and the cell growth almost cased. About 10 hours after replacing the gas phase, however, in spite of Po2 being still aroud 90 mmHg, a new synthesis of the nitrogenase as well as the cell growth started again. This new synthesis of the nitrogenase may be attributed to the acquisition of some protecting or tolerating mechanisms against high Po2.
社団法人日本農芸化学会の論文