Abstract
An investigation was made of various factors, both experimental and physiological, which influenced the formation of hydrogen gas by the heterocystous cyanobacterium Anabaena cylindrica B629 when incubated in both argon and air. A. cylindrica B629 produces hydrogen in air in the presence of carbon monoxide, acetylene, or both, with a short lag period. The rate of production in air at optimal concentrations of these compounds was found to be comparable with that in an argon atmosphere. Whereas under argon, ammonium ions (0.5 to 6 mM) were found to inhibit hydrogen formation in a manner which was dependent on light intensity and not relieved by oxygen (1 to 20% of gas phase), in air-carbon monoxide-acetylene, these ions (up to at least 0.5 mM) slightly stimulated hydrogen production for at least 24 h. Conclusions are drawn about short-term aerobic and anaerobic hydrogen formation by A. cylindrica B629 and the effects of ammonium ions, oxygen, carbon monoxide, and acetylene on these processes.