The effect of nickel on the growth, photosynthesis, and nitrogenase activity of Anabaena inaequalis

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Abstract
A. inaequalis was sensitive to Ni2+ in the order of decreasing sensitivity of growth, photosynthesis and acetylene reduction. At a culture density of 9 .times. 104 cells/ml, growth after 12 days was completely inhibited by 0.125 ppm (.mu.g/ml) Ni2+. Ni caused the increase of both the lag phase of growth and the culture doubling time, and caused the retardation phase to be sooner. Photosynthesis and acetylene reduction were completely inhibited by 10 and 20 ppm Ni2+, respectively, at a cell concentration of 1.3 .times. 106 cells/ml. Preincubation for 24 h in the presence of Ni2+ significantly increased the sensitivity of photosynthesis and acetylene reduction. Under these conditons acetylene reduction was more sensitive than photosynthesis. Ni2+ reduced culture growth by 35% at a level of 0.05 ppm and inhibited that culture''s acetylene-reducing ability by 29%, while leaving photosynthesis unaffected. Ni caused some damage to filament apical cells and induced pigment bleaching in aged cultures. Ni toxicity was probably due to poisoning of intracellular enzyme systems by Ni2+.

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