Effects of a Light to Dark Transition on Carbon Reserves, Nitrogen Fixation and ATP Concentrations in Cultures of Gloeocapsa (Gloeothece) sp. 1430/3

Abstract

Between 30 s and 5 min after transfer from light to darkness, the rate of acetylene reduction by cultures of the unicellular cyanobacterium Gloeocapsa sp. 1430/3 decreased rapidly. During the same period, there was a rapid disappearance of storage glucan. There was also a sharp fall in the intracellular concentration of ATP followed by a slower recovery. It is concluded that, in the dark, the catabolism of storage glucan is the only potential source of ATP and/or reductant and that the low rate of N2 fixation in the dark is not due to limitations in the supply of ATP.