Enzymes of the Calvin Cycle and Intermediary Metabolism in the Cyanobacterium Anacystis nidulans Grown in Chemostat Culture

Abstract

The cyanobacterium Anacystis nidulans grown in light-limited and C0,-limited chemostat cultures showed varying rates of CO, fixation with peaks at dilution rates of 0.10 to 0.12 h-l. The specific activities of a number of enzymes of the reductive and oxidative pentose phosphate and glycolytic pathways and the tricarboxylic acid and glyoxylate cycles varied significantly as a function of the growth environment (substrate limitation) and organism growth rate. Ribulose-l,5-bisphosphate carboxylase varied 15-fold under C0,-limited conditions but did not change under light-limited conditions. With the exception of phosphoribulokinase, all enzymes which showed a change in specific activity increased with decreasing dilution rate. The specific activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, hexokinase, ri bulose-1,5-bisphosphate carboxylase and malate dehydrogenase were significantly higher in organisms grown under C0,-limited conditions than under light-limited conditions. Fructose-1,6-bisphosphate aldolase and phosphoribulokinase specific activities were similar at all growth rates and under both limitations. Isocitrate lyase was the only enzyme examined which showed higher specific activities under light-limited conditions. Thus Anacystis nidulans can selectively express different enzymes, possibly by transcriptional control.

Genetic tagging, cloning, and DNA sequence of the Synechococcus sp. strain PCC 7942 gene (gnd) encoding 6-phosphogluconate dehydrogenase

“…strain PCC 7942 (formerly Anacystis nidulans R2 and here abbreviated as Synechococcus strain R2) gnd gene, which encodes 6-phosphogluconate dehydrogenase (6PGD), the third enzyme of the hexose monophosphate shunt. The level of this enzyme is higher in cells growing slowly in light-or C02-limited chemostats (15) and increases as exponentially growing cells make the transition into the stationary phase (S. E. Broedel, Jr., and R. E. Wolf, Jr., unpublished data), but it does not change during incubation in the dark (23).…”

Growth and Photosynthesis of the Cyanobacterium Synechococcus leopoliensis in HCO3−-Limited Chemostats

“…One previous study used chemostats to determine the effect of carbon-limitation on various enzyme levels in Synechococcus leopoliensis, but no information was given on the actual DIC concentrations at the various growth rates (18). Goldman and co-workers (12,13) have performed substantial chemostat studies with several species of green algae but did not report on the photosynthetic physiology of the cells.…”

Carbon dioxide fixation by Thiobacillus versutus: apparent absence of a CO2-concentrating mechanism in organisms grown under carbon-limitation in the chemostat

“…versutus was maintained and grown at 30 °C in chemostat culture as described previously [5,14]. Synechococcus PCC 7942 was also grown in continuous culture as described previously [16]. Aeration was with air + CO 2 mixtures passed at about 100 ml rain-1 through the cultures, and gas transfer to solution was assisted by a magnetically-driven double-paddle stirrer (LH Engineering) running at 750 rpm.…”

“…Biomass production and steady state concentrations and consumption rates in the chemostat were measured as described previously [16]. The ability of organisms taken directly from the chemostat to oxidize thiosulphate under conditions of excess supply was estimated as follows: samples (20 ml) of culture were placed in 250 ml conical flasks containing 1 ml 200 mM thiosulphate at 30 o C; duplicate samples (0.5 ml) were removed into the KCN-buffer mixture for cyanolysis assay [18] immediately and at 15 min intervals for 2 h. …”