Hydrogenase, nitrogenase, and hydrogen metabolism in the photosynthetic bacteria.

Publisher Summary This chapter illustrates the H 2 metabolism in photosynthetic bacteria. The developments in the context of the biochemistry and physiology of the photosynthetic bacteria, and their biotechnological applications are presented. Photosynthetic bacteria possess a diverse and evolutionarily ancient metabolism, which is reflected in the different ways in which they can metabolize H 2 . Three enzymes have been implicated in H 2 metabolism in these organisms: (1) nitrogenase, which catalyses unidirectional, ATP-dependent H 2 evolution, and can function either in the light, or in the dark under anaerobic or micro-aerobic conditions; (2) uptake hydrogenase, which is membrane-bound and, although capable of both H 2 evolution and uptake, functions physiologically in the direction of H 2 oxidation; and (3) “classical” or reversible hydrogenase, which may be either soluble or membrane bound and functions mainly during dark anaerobic fermentation. The photosynthetic bacteria represent a tool of great potential in various fields of biotechnology. Their rapid growth rate and their metabolic versatility enable them to survive and proliferate in a wide variety of environments.