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Electrochemically and Bioelectrochemically Induced Ammonium Recovery
Published on: January 22, 2015
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Ammonium uptake by Chlorella
1Pflanzenphysiologie, Universität Bayreuth, Universitätsstraße 30, D-8580, Bayreuth, Federal Republic of Germany.
Planta
|November 16, 2013
Summary
Glucose preincubation significantly enhances ammonium uptake in Chlorella by inducing a specific transport system. This glucose-induced ammonium transport is electrogenic and can also facilitate methylamine uptake.
Area of Science:
- * Algal Physiology and Biochemistry
- * Nutrient Transport Mechanisms in Microorganisms
Background:
- * Ammonium is a crucial nutrient for algal growth, and its uptake is tightly regulated.
- * Understanding the regulation of ammonium transport is vital for optimizing algal cultivation and biogeochemical cycling.
- * Previous studies suggested potential regulatory mechanisms for ammonium uptake, but the role of carbon sources was not fully elucidated.
Purpose of the Study:
- * To investigate the effect of glucose on ammonium uptake kinetics and the underlying transport system in Chlorella.
- * To elucidate the mechanistic details of the ammonium transport system, including its electrogenic nature and charge compensation.
- * To determine if glucose-induced changes in ammonium uptake affect the transport of other related molecules like methylamine.
Main Methods:
- * Chlorella cells were preincubated with glucose, and ammonium uptake rates and kinetics (K m, V max) were measured.
- * Time-course experiments were conducted to determine the lag period and stability of the induced transport system.
- * Mechanistic studies involved assessing the effects of specific inhibitors, light, and measuring ion fluxes (K+, H+) during ammonium uptake.
Main Results:
- * Glucose preincubation increased the maximal ammonium uptake rate (V max) tenfold without altering the affinity (K m).
- * A similar stimulation was observed when cells were transferred to a nitrogen-free medium, with a 10-20 minute lag period for glucose-induced stimulation.
- * The ammonium transport system exhibits a half-life of 5-10 hours, with light stabilizing activity for longer periods; 6-deoxyglucose did not induce this effect.
- * Evidence suggests an electrogenic ammonium uptake mechanism, compensated by K+ efflux and subsequent H+ extrusion.
- * Methylamine uptake was also enhanced in glucose-treated cells, indicating the involvement of the ammonium transport system.
Conclusions:
- * Glucose induces a specific ammonium transport system in Chlorella, likely mediated by a glucose metabolite.
- * The ammonium transport system is electrogenic and its activity is regulated by carbon availability and light.
- * The identified ammonium transport system also facilitates methylamine transport, highlighting its broader role in nitrogen assimilation.
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