Nitrite accumulation by Synechococcus 6301 as a consequence of carbon- or sulfur-deficiency

Abstract Air grown cultures of the cyanobacterium Synechococcus 6301, when incubated under continuous illumination with nitrate as the sole nitrogen source, started to liberate nitrite from the second day of inoculation. Nitrite accumulation depended on culture density and was caused by CO₂ deficiency since it could be prevented by addition of 5% CO₂ to the gas stream. Nitrite excreted during growth with air (0.035% CO₂) was taken up after an increase in CO₂ concentration to 5%.
In sulfur depleted cultures, nitrite excretion took place also with saturating CO₂ concentration. In this case nitrite accumulation could be reversed by addition of a suitable sulfur source.
Under both conditions for nitrite accumulation, carbon and sulfur deficiency, a significant decrease in nitrite reductase activity was observed which might account for nitrite liberation.