THE PREFERRED ELECTRON-ACCEPTOR OF DESULFOVIBRIO-DESULFURICANS CSN

The sulfate-reducing bacterium Desulfovibrio desulfuricans strain CSN (DSM 9104) oxidized H-2 with thiosulfate, sulfate, sulfite, nitrite, n itrate and oxygen with rates increasing (in the order listed) from 20 to 525 nmol H-2 min(-1) mg(-1) protein. Nitrate reduction was induced by nitrate or limiting concentrations of sulfate during growth, while all other activities were constitutive. Oxygen prevented reduction of all other electron accepters, while nitrate and nitrite blocked the re duction of the sulfur compounds. In the presence of H-2 and reduced su lfur compounds, H-2 was the preferred electron donor. The cells oxidiz ed thiosulfate or sulfite coupled to the reduction of nitrate to ammon ia. This represents a novel type of metabolism connecting the sulfur a nd nitrogen cycles. It is concluded that oxygen is the preferred elect ron acceptor of D. desulfuricans. Sulfate reduction in oxic environmen ts must be due to different organisms or mechanisms.