Glyoxylate Induced Changes in the Carbon and Nitrogen Metabolism of the Cyanobacterium Anabaena cylindrica

Abstract

Addition of millimolar concentrations of glyoxylate to nitrogen-fixing cultures of Anabaena cylindrica, grown aerobically in the light, caused the following effects: an increase in the number of glycogen granules and in the excretion of carbohydrates; a decreased phycocyanin concentration, but an increase in the chlorophyll a to phycocyanin ratio. Also, an enhancement in the carbon to nitrogen ratio was noted, but this was restored if NH4+ was added simultaneously. The most pronounced effect of glyoxylate addition was a 20-fold increase in the glycine pool. The effect of glyoxylate on N2 fixation (acetylene reduction) was enhanced at high light intensities, but it did not affect the in vitro ribulose-1,5-bisphosphate carboxylate activity. However, addition of millimolar concentrations of glycolate did not cause changes in nitrogenase activity, CO2 fixation, and NH3 release comparable to those caused by glyoxylate. The primary mechanism of action of glyoxylate appears to be within the glycolate pathway of the vegetative cells and metabolically downstream from glycolate.