Nitrogenase activity and nitrogen assimilation in Anabaena flos-aquae growing in continuous culture

✍ Scribed by Bone, Derek H.

• Publisher: Springer-Verlag
• Year: 1971
• Weight: 456 KB
• Volume: 80
• Category: Article
• ISSN: 0003-9276
• DOI: 10.1007/bf00410124

✦ Synopsis

Anabaena /los-aquae is grown in ehemostats under phosphate and urea-limited conditions, l~itrogenase activity in phosphate-limited cells has a maximum activity at a dilution rate of 0.025 h -1 and is repressed 24-fold by 15 mM KNO 3. Cultures growing on 1.5 mM nitrate obtain 1/2--2/3 of cell nitrogen from N2. Cells form inducible nitrite assimilating enzymes when grown on nitrate. Algae growing under A or He on limiting urea or phosphate-limited with nitrate have active nitrogenase. The ratio of nitrogenase activity to heterocyst numbers varied 90-fold depending on source of nitrogen, 15 mM KNO 3 gave the smallest ratio. The regulatory mechanisms controlling the activity of nitrogenase in blue-green algae is discussed.