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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.

The sulfate-reducing bacteria have been isolated from human intestine. These bacteria are identified by their morphological, physiological and biochemical characteristics as the Desulfovibrio sp. and Desulfomicrobium sp. according to Bergey’s Manual of Determinative Bacteriology. Growth of the isolated strains of bacteria has been studied under various conditions including types of media, effect of oxygen, pH, and tempe­rature. Bacterial growth in the modified Kravtsov-Sorokin’s medium, and process of dissimilatory sulfate reduction by the selected strains of bacteria have been investiga­ted. All obtained bacterial cultures used sulfate and lactate intensively as well as produced hydrogen sulfide and acetate in the medium. The Desulfovibrio sp. strain Vib-7 produced the highest concentration (up to 3.23 mM) of hydrogen sulfide, while the bacteria used about 99% of sulfate ions presented in the medium. This strain also produced the highest concentration of acetate ions (up to 15.87 mM) on the fifth day of cultivation. Among the studied Desulfomicrobium sp. strains, the highest concentration of hydrogen sulfide was produced by the Desulfomicrobium sp. strain Rod-9, and the highest concentration of acetate ions was produced by the Desulfomicrobium sp. strain Rod-4.

The aim of this research was to study the dissimilatory sulfate reduction process by various Desulfovibrio sp. strains of the human intestine, such as bacterial growth, sulfate- and lactate usage, production of sulfide and acetate by the strains, and carry out cluster and correlation analyses of this process. Methods. Microbiology methods of the study for bacterial strains cultivation and photometric methods for determination of bacterial biomass and hydrogen sulfide concentration were used, sulfate ions concentration was determined by turbidymetric method, lactate concentration was carried out by lactate dehydrogenase. Acetate ions accumulation by the strains was determined by titration. Using the experimental data, the methods of statistical analysis have been also used. Results. The various Desulfovibrio sp. strains accumulated different biomass for ten days of cultivation in modified Kravtsov-Sorokin’s medium. The highest biomass (up to 3.89 g/l) was accumulated by Desulfovibrio sp. strain Vib-7 on the sixth day of cultivation. Clustering of bacterial growth parameters has showed the greatest similarity between strains Desulfovibrio sp. strain Vib-7 and Desulfovibrio sp. strain Vib-9. After using all of the sulfate and lactate from the medium, the bacteria stopped growing and the stationary growth phase began. Clustering of the parameters of sulfate usage has showed that strains Desulfovibrio sp. Vib-1 and Desulfovibrio sp. Vib-2 were combined in one cluster, and the strains Desulfovibrio sp. Vib-7 and Desulfovibrio sp. Vib-9 were in another cluster. The strong correlation between all parameters of dissimilatory sulfate reduction (growth, reduction of sulfate, accumulation of sulfide, use of lactate and accumulation of acetate) by the Desulfovibrio sp. strains has been determined. Thus, the obtained results may be promising for further study, in particular for creating ulcerative colitis models, prediction and prevention of human inflammatory bowel disease.

New strains of sulfate-reducing bacteria from human intestine are obtained. These bacteria are vibrio-like (strains SRB Vib-1, SRB Vib-2, SRB Vib-3) and short rod-like (strains SRB Rod-4 and SRB Rod-5) forms. The growth of these strains of bacteria, usage of sulfates by bacteria and their production of hydrogen sulfide are investigated. The strains of sulfate-reducing bacteria SRB Vib-1, SRB Vib-2, SRB Vib-3 more intensively accumulate biomass, compared with strains SRB Rod-4 і SRB Rod-5. The strains SRB Vib-1 and SRB Vib-2 grow the most intensively. Accumulation of bacterial biomass (3.8 g/l) is the highest on the third day of cultivation, after that the stationary growth phase began. The strain of bacteria SRB Vib-3 accumulates biomass 2.89 g/l on the third day of bacteria cultivation. Maximal biomass of SRB Rod-4 and SRB Rod-5 bacteria strains ranged from 2.59 to 3.25 g/l on the eighth day of cultivation. The obtained sulfate-reducing bacteria intensively use sulfate ions and produce hydrogen sulfide. The strains SRB Vib-1, SRB Vib-2, SRB Vib-3 produce from 2.99 mM to 3.12 mM of hydrogen sulfide. The rod-shaped strains of sulfate-reducing bacteria use sulfate ions and produce hydrogen sulfide less intensely in the presence of sulfates in the medium.