Ammonia Uptake in the Alkalophilic Cyanobacterium Spirulina platensis

スポンサーリンク

概要

• 論文の詳細を見る

• Ammonia uptake was studied in the alkalophilic cyanobacterium Spirulina platensis. In continuous cultures under optimal growth conditions ammonia supported optimal growth (doubling time of 9.3 h), causing a reduction of glutamine synthetase activity to 25% of that found in cultures grown on NO_3^-. Long term (20 min) ammonia uptake assays were performed to study the dependency on metabolism: 1) Ammonia uptake proceeded at the same rates in the light and in the dark, the pH dependency pattern correlating with light-dependent O_2 evolution and dark O_2 consumption. 2) The uptake of ammonia was pH dependent with an optimum at pH 9.3. 3) The uptake was totally dependent upon the activity of glutamine synthetase and was completely inhibited by methoinine sulfoximine. To study the mechanism by which NH_4^+/NH_3 enters the cells, short term experiments (up to 1 min) were performed at pH 7.0 and pH 10.0: At pH 7.0 the uptake was slow and at a constant rate. At pH 10.0, the uptake did not saturate even at 1 mM ammonia and the kinetics were biphasic, consisting of a fast component lasting less than 5 seconds and of a subsequent slower component. The fast phase was insensitive to methionine sulfoximine, whereas the slower phase was completely inhibited by this compound. We suggest that under optimal (alkaline) pH the entry of ammonia into Spirulina cells is likely to be a ΔpH driven diffusion process, continuously supported by its intracellular assimilation.

• 日本植物生理学会の論文

著者

• Boussiba Sammy

  Microalgal Biotechnology Laboratory, The Jacob Blaustein Institute for Desert Research

• Boussiba S

  Ben‐gurion Univ. Negev Sede‐boker Campus Isr

• Boussiba Sammy

  Microalgal Biotechnology Laboratory Albert Katz Department Of Dryland Biotechnologies Jacob Blaustei

関連論文

• Astaxanthin Accumulation in the Green Alga Haematococcus pluvialis
• Parietochloris incisa comb. nov. (Trebouxiophyceae, Chlorophyta)
• The Biosynthetic Pathway of Astaxanthin in a Green Alga Haematococcus pluvialis as Indicated by Inhibition with Diphenylamine : ENVIRONMENTAL AND STRESS RESPONSES
• Isolation and Characterization of the Plasma Membrane by Two-Phase Partitioning from the Alkalophilic Cyanobacterium Spirulina platensis : MEMBRANES AND BIOENERGETICS
• Resistance of Spirulina platensis to Ammonia at High pH Values
• Ammonia Uptake in the Alkalophilic Cyanobacterium Spirulina platensis
• Presence of a Nonhydrolyzable Biopolymer in the Cell Wall of Vegetative Cells and Astaxanthin-Rich Cysts of Haematococcus pluvialis (Chlorophyceae)

スポンサーリンク