Uptake and Utilization of Sugar Phosphates by Anabaena flos-aquae

Abstract

The effect of various sugar phosphates on CO2 fixation in Anabacna flos-aquae was investigated and found to be very smilar to that found for isolated spinch chloroplasts. One exception, glucose 6-phosphate, has a stimulatory effect on CO2 fixation in Anabena but not in isolated chloroplast.Further examination of the role of glucose 6-phosphate metabolsm in The generally obligate nature of photoautotrophic growth in the blue-green algae has prompted the investigation of the biochemical basis for this growth habit. Although their mode of photosynthesis seems to be essentially identical to that of eucaryotic organisms (9), a blocked tricarboxylic acid cycle and a limited glycolytic cycle, due to the absence or low levels of phosphofructokinase (11,12,16,18), suggest that carbon flow in these organisms is either by a catabolic pentose phosphate shunt, as shown by Cheung and Gibbs (5), or by direct utilization of triose produced during photosynthetic carbon reduction. The questionable functioning of glycolysis and the tricarboxylic acid cycle, and the concomitant lack of ATP synthesis in the dark, might be the reason for limited growth on glucose or acetate (11,12,16).Recently, Pelroy and , have shown that turnover of glucose-6-P is restricted in the light and that rapid turnover occurs in the dark. Grossman and McGowan (6) have investigated the kinetics of glucose-6-P dehydrogenase in Anacystis and Anabaena and have determined regulation of the enzyme's catalytic activity by pH, NADPH, and ATP. These data suggest that if glucose-6-P could be assimilated in the dark, its turnover via the pentose phosphate pathway should go unhindered. However, it is generally believed that sugar phosphates are not assimilated by whole algal cells, or that if they are, they are first dephosphorylated at the cell membrane.In this study we present data which suggest that some sugar

Glucose Uptake in Prochlorococcus: Diversity of Kinetics and Effects on the Metabolism

“…The energetics of the glucose transport system of Prochlorococcus SS120 was also studied. Our initial hypothesis considered that glucose uptake could be most useful for Prochlorococcus under energy-limited conditions; however, we have shown that the glucose uptake rate was higher under light, with a circa 40% decrease when cells were subjected to darkness ( Gómez-Baena et al, 2008 ), in accordance with what has been described in previous studies on uptake of organic compounds ( Rubin et al, 1977 ; Church et al, 2004 , 2006 ; Michelou et al, 2007 ; Mary et al, 2008 ; Talarmin et al, 2011 ; Gómez-Pereira et al, 2013 ; Bjorkman et al, 2015 ). To evaluate if GlcH is a primary or secondary active transporter, we used different inhibitors of active transport to evaluate if GlcH is a primary or secondary active transporter (i.e., uses energy provided by ATP or from ionic gradients in order to take up glucose, respectively), namely monensin, valinomycin, DCCD, and CCCP.…”

Glucose Uptake and Its Effect on Gene Expression in Prochlorococcus

“…40% decrease when cells were subjected to darkness. In good agreement with these results, light also enhances the uptake of sugars in other cyanobacteria [28] , [29] , and that of amino acids in Prochlorococcus (50% increase) [13] , [29] .…”

Nutrient limitation dynamics of a coastal Cape Cod pond : seasonal trends in alkaline phosphatase activity

“…Anabaena sp. are notoriously hard to phosphate starve and it make take weeks to drive them to P starvation in culture (Rubin et al, 1977;Whitton et al, 1991). By analogy with the closely related Anabaena sp., we infer that Aphanizomenon sp.…”

“…Therefore, even when orthophosphate becomes depleted from the environment, organisms able to produce alkaline phosphatase will not be Plimited, but may be phosphate-deficient. Phosphate-deficiency is defined as the condition in which extracellular orthophosphate concentrations drop to levels at which cells can no longer maintain intracellular surplus-P. Phytoplankton have the ability to store surplus-P in the form of polyphosphates (polymers of orthophosphate) (Rubin et al, 1977;Reynolds, 1984). The mechanism by which surplus-P storage occurs is defined as luxury uptake.…”