Sodium chloride stimulated respiration of Anacystis nidulans

With certain salts a stimulation of respiration of the blue-green alga Anacystis nidulans was found in the dark. The stimulation was observed only at high concentrations (10(-2)M--10(-1)M). NaCl or LiCl are the most effective salts and on addition the increase of the respiration is about 2.5fold. Li is assumed to function as a substitute for Na. Potassium salts, except KCl, are ineffective. The order for the effectiveness is: NaCl greater than NaNO3, Na2SO4 greater than KCl greater than KNO3, K2SO4 (=zero). Accordingly, the cation Na+, and to a less degree the anion Cl- are responsible for the stimulatory effect. K, which is ineffective, is passively accumulated by Anacystis according to the membrane potential. Na is actively extruded. At 0.1 M external NaCl, the passive influx of Na is high, but even then it is balanced by an active efflux. This increases the energy consumption of the cells and leads to a stimulated respiration. With DCCD (N,N'-dicyclohexylcarbodiimide) or NEM (N-ethylmaleimide), the Na efflux is inhibited, simultaneously the stimulation of respiration is abolished and the passive influx of Na becomes detectable. At 0.1 M NaCl, the passive influx of Na measured in presence of DCCD is 5 x 10(-6) moles Na/min and ml packed cells. In absence of DCCD on addition of 0.1 M NaCl the extra oxygen consumption is 2 x 10(-6) moles O2/min and ml cells. This may prove that the stimulation of respiration is mainly caused by the active Na extrusion.