Abstract
In this article, we characterized the regularities of oxidation of nitrite ions by phototropic purple non-sulfur bacteria Rhodopseudomonas yavorovii IMV B-7620, which were isolated from the water of Yavorivske Lake (Lviv Region, Ukraine). The bacteria were cultivated anaerobically at the light intensity of 200 lux and aerobically without illumination for 13 days in the modified ATCC No. 1449 medium. The concentration of nitrite ions was determined turbidimetrically by the turbidity of the solution by method of diazotization of sulfanilic acid by the nitrite ions and the interaction of the formed salt with n-(l-naphtyl)ethylenediamine dihydrochloride. The concentration of nitrate ions was determined turbidimetrically by the turbidity of the solution by method of diazotization. Zinc powder was used as a reducing agent. Efficiency of oxidation of 0.7–5.6 mM nitrite ions as electron donors by these bacteria was 100–7%, on the 10-th day of cultivation. It was established that nitrate ions were accumulated in the medium as a result of oxidation of nitrite ions by bacteria. The largest biomass (1.6 g/L) bacteria accumulated on the thirteenth day of growth in a medium with 2.8 mM NO2–. We found that R. yavorovii can use nitrate ions and urea as the only source of nitrogen for phototrophic growth. At a concentration of 1.9 mM ammonium chloride, sodium nitrite and urea in the cultivation medium, the biomass of bacteria was 1.2, 0.8, 1.0 g/L, respectively. The ability of the studied microorganisms to oxidize nitrite ions and to use nitrate ions indicates the significant impact of purple non-sulfur bacteria on the redistribution of streams of nitrogen compounds in ecosystems and the essential role of these microorganisms in the nitrogen biogeochemical cycle.
Highlights
Nitrogen is a nutrient element of living cells and is part of many organic substances
In this research we investigated the ability of R. yavorovii to use various nitrogen compounds as a source of this element in assimilation processes at a concentration of 1.9 mM at an intensity of illumination of 200 lux in anaerobic conditions on 10th day of cultivation in the modified medium of ATCC No 1449
The largest biomass (1.2 g/L) of bacteria R. yavorovii accumulated in medium with ammonium chloride
Summary
Nitrogen is a nutrient element of living cells and is part of many organic substances In one or another form, it is located in all parts of the biosphere (Kozlova et al, 2008; Stein & Klotz, 2016). Anoxygenic phototropic bacteria populate the boundary of the aerobic and anaerobic zones, where light penetrates from above and compounds of sulfur, ferrum and hydrogen penetrate from the bottom. The growth of these microorganisms is often limited by the lack of reduced substrates (Lengeler et al, 2005)
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