[Hydrogen metabolism in Anabaena variabilis in the dark]

Cells and extracts of the cyanobacterium Anabaena variabilis are capable of hydrogen absorption in the dark in the presence of H-acceptors with various redox potentials. Preliminary adaptation of the cells to anaerobic conditions has no effect on the process. A. variabilis can also evolve hydrogen in the dark. Reduced methylviologen (RMV), formiate, pyruvate, and glucose may be substrates for hydrogen evolution by the cells. The extracts evolve hydrogen in the presence of RMV, benzylviologen, azocarmine, or NAD (P) H + ATP. No adaptation of the cells to anaerobic conditions is required for hydrogen evolution from RMV, and chloramphenicol has no effect on the process. The rate of hydrogen evolution is however higher in the cells adapted to anaerobic conditions. Production of hydrogen from pyruvate by the cells adapted and non-adapted to anaerobic conditions was detected only after their incubation with the substrate during 2--3 hours, and chloramphenicol inhibited the process.