New Zealand Journal of Marine and Freshwater Research abstracts

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Cyanobacterial ammonium transport, ammonium assimilation, and nitrogenase regulation

NIGEL W. KERBY

PETER ROWELL

WILLIAM D. P. STEWART

Agricultural and Food Research Council Research Group on Cyanobacteria Department of Biological Sciences University of Dundee Dundee DD1 4HN, United Kingdom

Abstract The growth of cyanobacteria in natural waters may be dependent on an efficient ammonium transport system. Such a system may also play a role in the retention of internally generated ammonium from N₂ fixation, nitrate reduction, and photorespiration. Methylammonium is commonly used as an ammonium analogue to study transport. The kinetics of methylammonium uptake by cyanobacteria are biphasic with a first rapid phase representing transport into the cells and a second slower phase dependent on metabolism by the primary ammonia assimilating enzyme glutamine synthetase. At high external pH values (pH > 9) diffusion of the uncharged species becomes increasingly dominant while at neutral pH values the uptake is thought to be an active process dependent on membrane potential.

Keywords ammonium transport; ammonia assimilation; blue-green algae; cyanobacteria; mutant strains; nitrogenase regulation

New Zealand Journal of Marine and Freshwater Research, 1987, Vol. 21: 447-455 0028-8330/87/2103-0447$2.50/0 © Crown copyright 1987 Received 19 February 1987; accepted 5 May 1987

PDF file of entire paper: medium quality (808K); (scanned from paper original: notes about this process)

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