Nitrogen fixation by Anabaena cylindrica

✍ Scribed by Weare, N. M. ;Benemann, John R.

• Book ID: 104761862
• Publisher: Springer-Verlag
• Year: 1973
• Weight: 573 KB
• Volume: 90
• Category: Article
• ISSN: 0003-9276
• DOI: 10.1007/bf00408927

✦ Synopsis

Blending Anabaena cylindrica cultures results in a loss of nitrogenase activity which is correlated with the breakage of the filaments at the junctions between heterocysts and vegetative cells. Oxygen inhibition of nitrogen fixation was significant only above atmospheric concentrations. Nitrogen-fixation activities in the dark were up to 500/0 of those observed in the light and were dependent on oxygen (10 to 20~ was optimal). ~itrogenase activity was lost in about 3 h when cells were incubated aerobically in the dark. l~e-exposure to light resulted in recovery of nitrogenase activity within 2 h. Blending, oxygen, or dark pre-incubation had similar effects upon cultures grown under air or nitrogen and did not inhibit light-dependent CO S fixation. We conclude that heterocysts are the sites of nitrogenase activity and propose a model for nitrogen fixation by Anabaena cylindrica.