Na+-stimulated nitrate uptake with increased activity under osmotic upshift in Synechocystis sp. strain PCC 6803 |
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Authors: | Baebprasert Wipawee Karnchanatat Aphichart Lindblad Peter Incharoensakdi Aran |
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Affiliation: | (1) Program of Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand;(2) Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand;(3) Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Bangkok, 10330, Thailand;(4) Department of Photochemistry and Molecular Science, Uppsala University, Box 523, 751 20 Uppsala, Sweden; |
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Abstract: | In the non-diazotrophic cyanobacterium Synechocystis sp. strain PCC 6803, an osmolality of 30 and 40 mosmol/kg sorbitol and NaCl resulted in 3.5- and 4.5-fold increase of nitrate uptake, respectively. The NaCl-stimulated uptake was abolished by treatment with chloramphenicol. At 25 mosmol/kg or higher, NaCl induced higher nitrate uptake than sorbitol suggesting an ionic effect of Na+. The nitrate uptake in Synechocystis showed K s and V max values of 46 μM and 1.37 μmol/min/mg Chl, respectively. Mutants disrupted in nitrate and nitrite reductase exhibited a decreased nitrate uptake. Ammonium, chlorate, and dl-glyceraldehyde caused a reduction of nitrate uptake. Dark treatment caused a drastic reduction of uptake by 70% suggesting an energy-dependent system. Nitrate transport was sensitive to various metabolic inhibitors including those dissipating proton gradients and membrane potential. The results suggest that nitrate uptake in Synechocystis is stimulated by Na+ ions and requires energy provided by the functioning electron transport chain. |
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