Metabolic peculiarities of the extremely alkaliphilic sulfate-reducing bacteria Desulfonatronum lacustre and Desulfonatronovibrio hydrogenovorans

The extremely alkaliphilic hydrogenotrophic bacteria Desulfonatronum lacust re and Desulfonatronovibrio hydrogenovorans utilize the acetyl-CoA pathway of carbon dioxide fixation and are characterized by high activities of both CO-dehydrogenase, the key enzyme of this pathway, and hydrogenase. Desulfo natronum lacustre contains two forms of hydrogenase-periplasmic and intrace llular-that differ in specific activity and sensitivity to specific inhibit ors of hydrogenases. The electron-transport chain includes cytochrome c loc alized in the periplasm. The study of the effect of ionophores and N,N-dicy clohexylcarbodiimide (DCCD) on Desulfonatronum lacustre and Desulfonatronov ibrio hydrogenovorans showed that sulfidogenesis is much more dependent on Na+-gradient when H-2, rather than formate or ethanol, is used as the elect ron donor. Complete inhibition of growth and sulfidogenesis in the presence of DCCD indicates that the energy metabolism of the bacteria studied depen ds on electron-transport phosphorylation by the chemiosmotic mechanism.