Transformation of sulfur and nitrogen compounds by sulfidogenic and phototrophic bacteria under the influence of sodium fluoride and potassium bromide

Abstract

Anthropogenically altered media are characterized by complex pollution, which contains a wide range of organic and inorganic pollutants, including halogen compounds. The influence of halides on transformed ecosystems, in particular, on their sulfidogenic and photosynthetic microbiota and its properties, remains insufficiently studied. The influence of sodium fluoride and potassium bromide at concentrations that are equal and 0.5–4.0 times differed from the maximum permissible concentrations (MPC) (MPC of fluorides and bromides are 0.0789 and 0.0025 mM, respectively) on the reduction of sulfate ions or sulfur (3.47 mM) by sulfidogenic bacteria of Desulfovibrio and Desulfuromonas genera, as well as on the use of thiosulfate or nitrite ions (4.167 mM) as electron donors of anoxygenic photosynthesis by phototrophic purple and green sulfur bacteria of Thiocapsa, Lamprocystis and Chlorobium genera, isolated from the Yavorivske Lake, was investigated. The biomass of bacteria was determined by the turbidimetric method, the content of H2S, SO42-, NО2ˉ and NО3ˉ in the cultural liquid – by the spectrophotometric method, the concentration of S2O32- – by the titrometric method. The intracellular glucose and glycogen content was determined enzymatically in cell-free extracts, using the analytical kit “Diagluc-2”. It was found that sodium fluoride and potassium bromide at concentrations 3.0–4.0 times higher than the MPC repress the biomass accumulation by bacteria Desulfovibrio sp. in the medium with sulfates 2.7−5.8 and 2.1−4.2 times, respectively, and inhibit the hydrogen sulfide production by them 1.8−3.4 and 2.0−3.2 times, respectively. NaF and KBr at concentrations that are equal and 2.0–4.0 times higher than the MPC repress the biomass accumulation by bacteria Desulfuromonas sp. in the medium with sulfur 2.2–6.9 and 2.1–5.6 times, respectively, and at concentrations 3.0–4.0 times higher than the MPC inhibit the hydrogen sulfide production by bacteria 1.9−3.7 and 2.0−2.7 times, respectively. Sodium fluoride and potassium bromide at concentration that 4.0 times exceeded the MPC inhibit the biomass accumulation by bacteria of Thiocapsa, Lamprocystis and Chlorobium genera in the medium with thiosulfates 2.0–2.3 and 1.7–2.0 times, respectively, reduce thiosulfate ions oxidation by them by 31.9–38.5 and 27.1–33.7%, respectively, compared to the control, but stimulate glycogen synthesis by cells of green sulfur bacteria by 106.7 and 64.0%, respectively. NaF and KBr at concentration 4.0 times higher than the MPC inhibit the biomass accumulation by phototrophic bacteria in the medium with nitrites 2.1−2.4 and 1.8−1.9 times, respectively, slow down nitrite ions oxidation by bacteria by 23.5–26.1 and 17.1–20.1%, respectively, compared to the control, but stimulate glycogen synthesis by cells of green sulfur bacteria by 134.7 and 115.0%, respectively. Glycogen content in Chlorobium limicola IMV K-8 cells grown in the media with Na2S2O3 or NaNO2 and NaF at concentration that 4.0 times exceeded the MPC was 81.33 and 84.13 mg/g of dry weight of cells, respectively. Fluoride ions showed a greater toxic effect on bacteria than bromide ions. The resistance of all tested bacteria strains to inorganic pollutants at high concentrations indicates their high biotechnological potential.