Energy Supply System for the Gliding Movement of Hormogonia of the Cyanobacterium Nostoc cycadae

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The effects of selected metabolic inhibitors and light on the gliding movement of the hormogonia of the cyanobacterium Nostoc cycadae were examined. Respiratory poisons (sodium cyanide, sodium azide) stopped the movement in the dark, but not in light. DCMU had little effect on the movement in light. The inhibitory effect of monoiodoacetic acid (MIA) on the gliding movement in light was restored by adding DCMU, suggesting that the gliding movement in light is linked to a cyclic electron flow involving photosystem I, not to a noncyclic electron flow involving photosystem II. This was then proved by experiments on the effects of selected wavelengths of light on the movement; light absorbed by chlorophyll was found to accelerate the movement, but that absorbed by phycobilins did not. The proton-conducting uncouplers carbonyl cyanide m-chlorophenylhydrazone (CCCP) and 2,4-dinitrophenol (DNP) immediately abolished the movement. Arsenate or N,N'-dicyclohexylcarbodiimide (DCCD), known inhibitors of ATP synthesis, had little effect on the movement. Light irradiation caused acidification of the cell suspension. From these results, the direct driving force for the gliding movement of this organism seems to be the trans-cell membrane electrochemical potential difference of protons, generated by a respiratory chain in the dark and a cyclic photoelectron flow system in light.
日本植物生理学会の論文