Na+-stimulated phosphate uptake system in Synechocystis sp. PCC 6803 with Pst1 as a main transporter

Abstract

BackgroundMost living cells uptake phosphate, an indispensable nutrient for growth from their natural environment. In Synechocystis sp. PCC 6803, the cells lack phosphate-inorganic transport (Pit) system but contain two phosphate-specific transport (Pst) systems, Pst1 and Pst2. We investigated the kinetics of Pi uptake of these two Pst systems by constructing the two mutants, ΔPst1 and ΔPst2, and comparing their kinetic properties with those of the wild-type cells under both Pi-sufficient and deficient conditions. The effects of pH and Na+ on the uptake of phosphate in Synechocystis were also studied.ResultsGrowth rates of the two mutants and wild type were similar either under phosphate-sufficient or deficient condition. The Km for phosphate uptake was 6.09 μM in wild type and this was reduced to 0.13 μM in ΔPst1 cells and 5.16 μM in the ΔPst2 strain. The Vmax values of 2.48, 0.22, and 2.17 μmol • (min • mg of chlorophyll a)-1 were obtained for wild type, the ΔPst1 and ΔPst2 strains, respectively. A monophasic phosphate uptake was observed in wild-type cells. The uptake of phosphate was energy and pH-dependent with a broad pH optimum between pH 7-10. Osmolality imposed by NaCl stimulated phosphate uptake whereas that imposed by sorbitol decreased uptake, suggesting stimulation of uptake was dependent upon ionic effects.ConclusionThe data demonstrate that Pst2 system of Synechocystis has higher affinity toward phosphate with lower Vmax than Pst1 system. The Pst1 system had similar Km and Vmax values to those of the wild type suggesting that Pst1 is the main phosphate transporter in Synechocystis sp. PCC 6803. The Km of Pst1 of Synechocystis is closer to that of Pit system than to that of the Pst system of E. coli, suggesting that Synechocystis Pst1 is rather a medium/low affinity transporter whereas Pst2 is a high affinity transporter.

Role of Type 2 NAD(P)H Dehydrogenase NdbC in Redox Regulation of Carbon Allocation in Synechocystis

“…The transport of various nutrients, like potassium and metal ions, amino acids, and polysaccharides (Table III), demonstrated marked down-regulation in the DndbC mutant except for the HCO 3 2 transporter BCT1 (Omata et al, 1999), which was up-regulated in the DndbC mutant compared with the wild type. The strongest down-regulation was observed for both ABC-type inorganic phosphate transporters (Table III), the constitutive low-affinity phosphate transporter Pst1 and the inducible, highaffinity phosphate transporter Pst2 (Pitt et al, 2010;Burut-Archanai et al, 2011). Furthermore, in the DndbC mutant, the levels of enzymes involved in nitrogen uptake, NRT transporters responsible for nitrate and nitrite uptake, as well as urea and ammonium transporters were down-regulated (Table III).…”

Repeated phosphate removal from recirculating aquaculture system using cyanobacterium remediation and chitosan flocculation

“…They can take up phosphate directly under a broad pH range (Burut‐Archanai et al . ) and store it intracellularly in the form of polyphosphate granules (Burut‐Archanai et al . ).…”

Physiological, biochemical and molecular responses of the halophilic cyanobacteriumAphanothece halophyticato Pi-deficiency

“…Thus, under P deficiency, cells bypass Pi and ATP-dependent enzymes in favour of PPi-dependent glycolytic enzymes, a process known as 'energetic flexibility' (Dobrota, 2006). In freshwater cyanobacteria, salinity severely reduces the cellular P-quota (Rai & Tiwari, 1999a;Rai & Sharma, 2006;Burut-Archanai et al, 2011, Tripathi et al, 2012, leading to depletion of cellular ATP (Avendaño & Valiente, 1994).…”