Regulation of ammonium/methylammonium transport by ammonium in the cyanobacterium Anabaena variabilis

Abstract

The ammonium transport system of Anabaena variabilis Kütz ATCC 29413 was studied with regard to its repression and derepression using [14C]‐methylammonium as an analogue for ammonium. Whereas N2‐grown cells showed an active ammonium transport system, the latter was repressed in ammonium‐grown cells. Repression of the ammonium transport system by ammonium did not require ammonium assimilation or de novo protein synthesis, suggesting that ammonium itself was the repressor signal. The derepression of the ammonium transport system however, required de novo protein synthesis and glutamine synthetase activity.

Evidence for the occurrence of a specific methylammonium transport system in the cultured cyanobiont of the Anthoceros punctatus-Nostoc association

“…In contrast, ammonium-grown cells showed no [ 4C]methylammonium uptake (Fig. l), consistent with reports suggesting ammonium transport system repression in ammoniumgrown bacterial and cyanobacterial cells (Kleiner, 1985 ;Rai et al, 1986;Rai & Prakasham, 1989 distinct a biphasic pattern, and the uptake rate in methylammonium-grown cells was about five-fold higher than that of N2-grown cells during the second phase (Fig. 1).…”

Ammonia translocation in cyanobacteria

“…The interpretation of derepression kinetics in unicellular forms, as is the case with diazotrophic strains, is complicated by the accompanying nitrogen deficiency and need for synthesis of enzymes for utilizing the new nitrogen source, whether this be nitrate or dinitrogen. However, a rise in CH3NH~" uptake becomes apparent within 1-2 h, and is dependent on new protein synthesis [50,51]. These experi.…”