Genetic control of ammonium transport in nitrogen fixing cyanobacterium Nostoc muscorum

Bacterial ammonium transport

“…With respect to NH~ transport, however, no evidence was found by us or reported in the literature for the derepression of a second NH~ carrier under conditions of high NH~ supply. Only in N. muscorum are two NH~ transport systems synthesized [15], but the high-affinity system seems to be constitutive (A.K. Kashyap, personal communication).…”

Ammonium transport in thermophilic cyanobacterium Synechococcus elongatus.

“…This was further substantiated by isolation of mutants where one of the two transport systems was either absent or modified (7,9).…”

“…On the other hand, based on the saturation kinetics of NH4 uptake, two transport systems have been found in Nostoc muscorum (7), N. calcicola (13) and Anacystis nidulans (9). This was further substantiated by isolation of mutants where one of the two transport systems was either absent or modified (7,9).…”

“…Occurrence of an ammonium transport system (ATS) has been described for nitrogen (N2)-fixing and non-N2-fixing cyanobacteria (4,7,9,(13)(14)(15)(16). It was demonstrated that N2-fixing cyanobacteria exhibit two phases during transport of methylammonium, an analog of ammonium (NH).…”

“…The intracellular pool of NH4 was determined as described in ref. 7. Kinetic constants were determined from Lineweaver-Burk (10) plots.…”