Membrane electrogenesis and sodium transport in filamentous nitrogen-fixing cyanobacteria

Apte, Shree Kumar ; Thomas, Joseph (1986) Membrane electrogenesis and sodium transport in filamentous nitrogen-fixing cyanobacteria European Journal of Biochemistry, 154 (2). pp. 395-401. ISSN 0014-2956

PDF - Publisher Version

Official URL:

Related URL:


Transport of Na+ and its relationship with membrane potential (Δψm) was examined in Anabaena L-31 (a fresh water cyanobacterium) and Anabaena torulosa (a brackish water cyanobacterium) which require Na+ for diazotrophic growth. The data on the effect of N,N'-dicyclohexylcarbodiimide indicated that Δψm was generated by electrogenic proton extrusion predominantly mediated by ATPase(s). In addition, operation of a plasmalemmabound, non-ATP-requiring, H+ -pumping terminal oxidase was suggested by the sensitivity of Δψm to anaerobiosis, cyanide and azide, all of which inhibit aerobic respiration. The response of Δψm to external pH and external Na+ or K+ concentrations indicated that a diffusion potential of Na+ or K+ may not contribute significantly to Δψm. Kinetic studies showed that Na+ influx was unlikely to be a result of Na+/Na+ exchange but was a carrier-mediated secondary active transport insensitive to low concentrations (< 10 mM) of external K+. There was a close correspondence between changes in Δψm and Na+ influx; all the treatments which caused depolarisation (such as low temperature, dark, cyanide, azide, anaerobiosis, ATPase inhibitors) lowered Na+ influx whereas treatments which caused hyperpolarisation (such as 2,4-dinitrophenol, nigericin) enhanced Na+ influx. Remarkably low intracellular Na+ concentrations were maintained by these cyanobacteria by means of active efflux of the cation. The basic mechanism of Na+ transport in the fresh water and the brackish water cyanobacterium was similar but the latter demonstrated less influx, more efficient efflux, more affinity of carriers for Na+ and less accumulation of Na+, all attributes favouring salt tolerance.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
ID Code:792
Deposited On:25 Sep 2010 04:47
Last Modified:16 May 2016 11:59

Repository Staff Only: item control page