Abstract
An ammonium transport system in the phototrophic N2-fixing bacteriumRhodospirillum rubrum was characterized by using the uptake of14C-methylamine as a probe.
Uptake showed saturation kinetics with an apparentK m =110 μM. It was competitively inhibited by ammonium (K i =7 μM). Uptake exhibited a narrow pH maximum around pH 7.0.
Up to 200-fold gradients across the membrane were formed within 40–60 min. Gradient formation was inhibited by carbon starvation, azide or cyanide. Pre-accumulated methylamine was released by ammonium pulses to more than 80%, indicating only minor metabolization.
The synthesis of the transport system was repressed by ammonium in high concentrations.
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Alef, K., Kleiner, D. Evidence for an ammonium transport system in the N2-fixing phototrophic bacteriumRhodospirillum rubrum . Arch. Microbiol. 132, 79–81 (1982). https://doi.org/10.1007/BF00690822
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DOI: https://doi.org/10.1007/BF00690822