Hydrogen metabolism by filamentous cyanobacteria

Abstract

Apparent discrepancies in the literature concerning the amounts of H 2 produced by strains of Anabaena cylindrica are explained. These are not due to differences in strains used by different workers nor to differences in growth conditions, but rather appear to be due to the fact that cultures show an increasing dependence with age on CO 2 for sustained H 2 production. Two distinct hydrogenase activities were measured and characterized, both in vivo and in vitro in A. cylindrica B629; these were H 2 uptake activity and H 2 evolution from reduced methyl viologen. Gentle cell disruption techniques were used to gain further evidence that the latter activity was soluble. H 2 uptake was strongly inhibited by acetylene in vivo in the light or in the dark with phenazine methosulfate added, but only after a prolonged lag period. In extracts this lag did not occur. A detailed study of the nitrogenase and hydrogen uptake activities and their interrelationship both in the light and in the dark in A. cylindrica B629 showed that only in the dark in the presence of O 2 did H 2 uptake support C 2H 2 reduction significantly. Under several conditions in which nitrogenase activity was inhibited H 2 uptake was unaffected. H 2 metabolism was tested in three nonheterocystous filamentous cyanobacteria under different growth and incubation conditions. These were Plectonema boryanum, Schizothrix calcicola, and Oscillatoria brevis. Myxosarcina chroococcoides and Fischerella muscicola were also investigated. Cyanobacterial species vary markedly in their hydrogen metabolism and in the composition of the three H 2 metabolizing enzymes.