The effect of osmotic stress on the oxidation of glycolate by the blue-green alga Anacystis nidulans

Abstract

Anacystis nidulans Richt. was shown to assimilate glycolic acid, and uptake was light-stimulated. In the dark 90% of the glycolate taken up was oxidised to CO₂. Both light and dark uptake was completely inhibited by α-hydroxysulphonates but was unaffected by isonicotinyl hydrazide. 3-(3,4-Dichlorophenyl)-1,1-dimethyl urea (DCMU) reduced the rate of light uptake but not to the uptake level of the dark control. Subjecting the algal cells to osmotic stress by incubation in 0.6 M mannitol for 1 h, which reduces the photosynthetic activity of this alga, causes an 80% reduction in both light and dark glycolate uptake although the uptake of glyoxylate, formate, acetate, and glycine is not markedly affected. Osmotic stress had no effect on the uptake and metabolism of glycolate by Anabaena flos-aquae (Lyngbye) Bred. and Oscillatoria sp. The activity of glycolate dehydrogenase in Anacystis was also reduced by osmotic shock while the activity of other enzymes was unaffected.