Reduction of sulfate, nitrate and nitrite ions by Desulfovibrio sp. under the influence of ferrum (III) citrate

Abstract

The influence of ferrum (III) citrate added to the cultivation medium, on the reduction of sulfate, nitrate, and nitrite ions by sulfate-reducing bacteria Desulfovibrio desulfuricans IMV K-6, Desulfovibrio sp. Yav-6, and Desulfovibrio sp. Yav-8 isolated from Yavorivske Lake was studied. It was established that ferrum (III) citrate inhibits the biomass accumulation, SO42- reduction, and H2S production by the bacteria after addition of 1.74–3.47 mM Na2SO4×10 H2O and 1.74–10.41 mM FeC6H5O7 to the medium, in comparison with the growth and level of the reduction of sulfate ions by bacteria in the medium supplemented with only Na2SO4×10 H2O. At conditions of the bacteria cultivation in the presence of an equimolar amount (3.47 mM) of Na2SO4×10 H2O and FeC6H5O7, they reduced 2.5−2.7 times more Fe(ІІІ) than SO42- with Fe2+ production at a concentration 2.4−2.7 times greater than H2S. FeC6H5O7 inhibited growth, NO3- or NO2- reduction and NH4+ production by the bacteria in the presence of 1.74−3.47 mM NaNO3 or NaNO2 and 1.74−10.41 mM FeC6H5O7 in the medium, compared to the growth and level of nitrate or nitrite ions reduction in the medium with only NaNO3 or NaNO2. In the medium with the same initial content of 3.47 mM NaNO3 and 3.47 mM FeC6H5O7, the bacteria reduced 1.4 times more NO3- than Fe(ІІІ), with NH4+ production at concentration 1.1 times higher than that of Fe2+. In the medium with 3.47 mM NaNO2 and 3.47 mM FeC6H5O7, the cells reduced 1.4−1.6 times more Fe(ІІІ) than NO2-, with Fe2+ production at concentra­tion 1.5−1.6 times higher than NH4+. Ferrum (III) citrate had more inhibitory effect on the dissimilatory reduction of sulfate by the bacteria than of nitrate and nitrite ions, since the SO42- reduction by the bacteria at its presence in the medium decreased 2.0−4.7 times. The reduction of NO3- and NO2- decreased only 1.3−1.9 and 1.7−3.1 times, respectively, as compared with their reduction in the media with only Na2SO4×10 H2O, NaNO3 or NaNO2. Despite the fact that the reduction by cells of 1.74−10.41 mM Fe(III) in the media with Na2SO4×10 H2O, NaNO3 or NaNO2 decreased 1.1−2.1, 1.6−2.7 and 1.1−2.5 times, respectively, compared with its reduction in the medium with only FeC6H5O7. The investigated strains of bacteria were resistant to high concentrations of ferrum (III) citrate and, therefore, can be applied in the technologies of complex environment purification from pollution with ferrum, sulfur, and nitrogen compounds.

Keywords

• desulfovibrio
• ferrum
• sulfates
• nitrates