Induction of H2-Uptake and Nitrogenase Activities in the Cyanobacterium Anabaena variabilis ATCC 29413: Effects of Hydrogen and Organic Substrate

A comparative study of the development of uptake hydrogenase and nitrogenase activities in cells of the cyanobacterium Anabaena variabilis was performed. The induction of heterocysts is followed by the induction of both in vivo hydrogen uptake and nitrogenase activities. Interestingly, a low but significant H₂-uptake 2–7 μmoles of H₂ · mg⁻¹ (Chl a) · h⁻¹] occurs in cultures with no heterocysts and with no nitrogenase activity. A slight stimulatory effect (30–40%) of H₂ on in vivo H₂-uptake was observed during the early stages of nitrogenase induction. However, exogenous H₂ does not further stimulate the induction of in vivo hydrogen uptake observed during heterocyst differentiation. Similarly, organic carbon (fructose) did not influence the induction of either in vivo hydrogen uptake or nitrogenase activities. Exogenous fructose supports higher in vivo hydrogen uptake and nitrogenase activities when the cells enter late exponential phase of growth. Received: 22 November 1995 / Accepted: 22 December 1995