ISSN:
1432-072X
Keywords:
Heterocyst
;
Blue-green algae
;
Anabaena
;
Nitrogenase
;
Hydrogenase
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Isolated heterocysts of Anabaena 7120 evolve H2 in an ATP-dependent nitrogenase-catalyzed process that is inhibited by N2 and C2H2. Heterocysts have an active uptake hydrogenase that only requires an electron acceptor of positive redox potential, e.g., methylene blue, dichlorophenolindophenol or potassium ferricyanide. O2 supplied at low partial pressures is a very effective physiological oxidant for H2 uptake. High concentrations of O2 are inhibitory to H2 uptake. The oxyhydrogen reaction in heterocysts appears to be mediated by a cytochrome-cytochrome oxidase system, and it supports ATP synthesis via oxidative phosphorylation. Attempts to demonstrate acetylene reduction in isolated heterocysts employing H2 as an electron donor were unsuccessful. It is suggested that the uptake hydrogenase functions to conserve reductant that otherwise would be dissipated via nitrogenase-catalyzed H2 evolution.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00406027
Permalink
