Abstract
We have compared the characteristics of nitrate uptake by Aphanothece halophytica grown under non-stress and salt-stress conditions. Both cell types showed essentially similar patterns of nitrate uptake toward ammonium, nitrite, and DL-glyceraldehyde. Although the affinities of nitrate to non-stress cells and salt-stress cells were not significantly different, i.e., Ks = 416 and 450 µM, respectively, the Vmax value for non-stress cells was about twofold of that for salt-stress cells (9.1 vs 5.3 µmol min–1 mg–1 Chl). Nitrate uptake by A. halophytica was found to be dependent on Na+. Ammonium inhibited nitrate uptake, and the presence of methionine sulfoximine could not release the inhibition by ammonium. Nitrite appeared to competitively inhibit nitrate uptake with a Ki value of 84 µM. Both chloride and phosphate anions did not affect nitrate uptake. DL-Glyceraldehyde, an inhibitor of CO2 fixation, caused a reduction in the uptake of nitrate.
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Received: 22 October 2002 / Accepted: 6 December 2002
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Incharoensakdi, A., Wangsupa, J. Nitrate Uptake by the Halotolerant Cyanobacterium Aphanothece halophytica Grown Under Non-Stress and Salt-Stress Conditions. Curr Microbiol 47, 0255–0259 (2003). https://doi.org/10.1007/s00284-002-4000-6
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DOI: https://doi.org/10.1007/s00284-002-4000-6