The patterns of utilization of sulfate and nitrate ions by bacteria Desulfomicrobium sp. CrR3 and Desulfovibrio desulfuricans Ya-11

Abstract

The aim of this work was to study the patterns of utilization of sulfate and nitrate ions by bacteria Desulfomicrobium sp. CrR3 and Desulfovibrio desulfuricans Ya-11 under different cultivation conditions. Chromium-resistant sulfate-reducing bacteria Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11 were used. Bacteria were grown in Posgate C medium at 30°C in 25 ml test tubes under anaerobic conditions. To test the ability of bacteria Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11 to use various substances and ions as electron acceptors, they were incubated in potassium phosphate buffer (10 mM, pH 7) with sulfate, nitrate and nitrite ions in concentrations of 1, 5 and 10 mM. At various concentrations of sulfate ions (1, 5 and 10 mM), biomass of bacteria Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11 increased with the increase of concentration of electron acceptor, the maximum biomass was equal to 3.65 and 3.05 g/l at 10 mM of sulfate ions, respectively. With the increase of concentration of nitrate ions to 5 mM the biomass increased by 70% compared to the biomass of bacteria grown in the medium with nitrate ions at the concentration 1 mM. The maximal biomass was determined in the presence of nitrate ions at a concentration of 10 mM – 3.78 and 3.15 g/l for bacteria Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11, respectively. It is found, as a result of incubation of bacteria Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11, that by introducing sulfate ions at a concentration of 5 mM bacteria Desulfomicrobium sp. CrR3 used 98%, while D. desulfuricans Ya-11 used only 86%, and under these conditions hydrogen sulfide has been detected in the incubation mixture at the concentration of 0.8–1.0 mM. In the presence of 10 mM of sulfate ions efficiency of electron acceptors utilization was equal to 85–95% for both strains. Bacteria Desulfomicrobium sp. CrR3 intensively used nitrate ions, the efficiency of electron acceptor utilization at 10 mM was equal to 92.8%, while for D. desulfuricans Ya-11 the usage percent amounted to 73% only, and nitrite ions were not observed after three days of incubation. It is established that bacteria Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11 are capable to use sulfate and nitrate ions as electron acceptors in the process of the disimilatory sulfate and nitratre reduction. As a result of the study of patterns of nitrate utilization by Desulfomicrobium sp. CrR3 and D. desulfuricans Ya-11 it is found that bacteria use nitrate as a nitrogen source for biosynthetic processes, and as electron acceptors. Under these conditions nitrates are reduced to nitrites, and then they are turned to ammonium.

Keywords

• sulfate-reducing bacteria
• sulfate reduction
• nitrate reduction