Absence of the glutamine-synthetase-linked methylammonium (ammonium)-transport system in the cyanobiont ofCycas-cyanobacterial symbiosis

✍ Scribed by A. N. Rai; P. Lindblad; B. Bergman

• Book ID: 104752881
• Publisher: Springer-Verlag
• Year: 1986
• Tongue: English
• Weight: 299 KB
• Volume: 169
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00392134

✦ Synopsis

Using the ammonium analogue (14)CH3NH 3 (+) , ammonium transport was studied in the cyanobiont cells freshly isolated from the root nodules of Cycas revoluta. An L-methionine-DL-sulphoximine (MSX)-insensitive ammonium-transport system, which was dependent on membrane potential (ΔΨ), was found in the cyanobiont. However, the cyanobiont was incapable of metabolizing exogenous (14)CH3NH 3 (+) or NH 4 (+) because of the absence of another ammonium-transport system responsible for the uptake of ammonium for assimilation via glutamine synthetase (EC 6.3.1.2). Such a modification seems to be the result of symbiosis because the free-living cultured isolate, Anabaena cycadeae, has been shown to possess both the ammonium-transport systems.