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Abstract
Summary: Gloeocapsa sp. 1430/3 fixed N2 in the dark, but at a lower rate than in the light. Following the transfer of exponentially growing cultures to the dark, the rate of N2 fixation increased for between 2 and 5 h and then decreased, becoming negligible after 12 h. No substantial increase in activity occurred for about 10 h following re-illumination. It is suggested that the decrease in nitrogenase activity which occurred about 5 h after transfer to the dark was not caused by exhaustion of carbon reserves but by a cessation of nitrogenase synthesis coupled with an irreversible inactivation of the enzyme, probably by O2. Subsequent recovery of activity apparently depended upon resynthesis of nitrogenase.
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© Society for General Microbiology, 1981