Nitrite

About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.

Degradation of n-Hexadecane and Its Metabolites by Pseudomonas aeruginosa under Microaerobic and Anaerobic Denitrifying Conditions

Abstract: A strategy for sequential hydrocarbon bioremediation is proposed. The initial O2-requiring transformation is effected by aerobic resting cells, thus avoiding a high oxygen demand. The oxygenated metabolites can then be degraded even under anaerobic conditions when supplemented with a highly water-soluble alternative electron acceptor, such as nitrate. To develop the new strategy, some phenomena were studied by examining Pseudomonas aeruginosa fermentation. The effects of dissolved oxygen (DO) concentration on n-hexadecane biodegradation were investigated first. Under microaerobic conditions, the denitrification rate decreased as the DO concentration decreased, implying that the O2-requiring reactions were rate limiting. The effects of different nitrate and nitrite concentrations were examined next. When cultivated aerobically in tryptic soy broth supplemented with 0 to 0.35 g of NO2−-N per liter, cells grew in all systems, but the lag phase was longer in the presence of higher nitrite concentrations. However, under anaerobic denitrifying conditions, even 0.1 g of NO2−-N per liter totally inhibited cell growth. Growth was also inhibited by high nitrate concentrations (>1 g of NO3−-N per liter). Cells were found to be more sensitive to nitrate or nitrite inhibition under denitrifying conditions than under aerobic conditions. Sequential hexadecane biodegradation by P. aeruginosa was then investigated. The initial fermentation was aerobic for cell growth and hydrocarbon oxidation to oxygenated metabolites, as confirmed by increasing dissolved total organic carbon (TOC) concentrations. The culture was then supplemented with nitrate and purged with nitrogen (N2). Nitrate was consumed rapidly initially. The live cell concentration, however, also decreased. The aqueous-phase TOC level decreased by about 40% during the initial active period but remained high after this period. Additional experiments confirmed that only about one-half of the derived TOC was readily consumable under anaerobic denitrifying conditions.

A Nitrite Transporter Associated with Nitrite Uptake by Higher Plant Chloroplasts

Abstract: Chloroplasts take up cytosolic nitrite during nitrate assimilation. In this study we identified a nitrite transporter located in the chloroplasts of higher plants. The transporter, CsNitr1-L, a member of the proton-dependent oligopeptide transporter (POT) family, was detected during light-induced chloroplast development in de-etiolating cucumber seedlings. We detected a CsNitr1-L-green fluorescent protein (GFP) fusion protein in the chloroplasts of leaf cells and found that an immunoreactive 51 kDa protein was present in the isolated inner envelope membrane of chloroplasts. CsNitr1-L has an isoform, CsNitr1-S, with an identical 484 amino acid core sequence; however, in CsNitr1-S the 120 amino acid N-terminal extension is missing. Saccharomyces cerevisiae cells expressing CsNitr1-S absorbed nitrite from an acidic medium at a slower rate than mock-transformed control cells, and accumulated nitrite to only one-sixth the concentration of the control cells, suggesting that CsNitr1-S enhances the efflux of nitrite from the cell. Insertion of T-DNA in a single CsNitr1-L homolog (At1g68570) in Arabidopsis resulted in nitrite accumulation in leaves to more than five times the concentration found in the wild type. These results show that it is possible that both CsNitr1-L and CsNitr1-S encode efflux-type nitrite transporters, but with different subcellular localizations. CsNitr1-L may possibly load cytosolic nitrite into chloroplast stroma in the chloroplast envelope during nitrate assimilation. The presence of genes homologous to CsNitr1-L in the genomes of Arabidopsis and rice indicates that facilitated nitrite transport is of general physiological importance in plant nutrition.

Purification and properties of a copper-containing nitrite reductase from a denitrifying bacterium, Alcaligenes faecalis strain S-6.

Abstract: A copper-containing nitrite reductase was purified and crystallized from a potent denitrifying bacterium, Alcaligenes faecalis strain S-6. The enzyme was composed of 4 subunits with a molecular weight of about 30,000, each containing 1 atom of Cu2+. Nitric oxide was identified as a main reduction product from nitrite in the enzyme-catalyzed reaction. The enzyme activity was inhibited strongly by KCN but only slightly by sulfhydryl reagents such as p-chloromercuribenzoate and N-ethylmaleimide.

Influence of Denitrification on the Corrosion of Iron and Stainless Steel Powder

Abstract: The purpose of this research was to address the anoxic oxidation of metallic iron and stainless steel powder by nitrate, nitrite, and anaerobic mixed cultures. In sterile batch reactors, both nitrate and nitrite(10 mg N/L) could chemically oxidize metallic iron, with a concomitant reduction to ammonium. Nitrate or nitrite reduction coupled to metal corrosion was not observed in the case of stainless steel powder. Combination of an anaerobic mixed culture and metallic iron led to (cathodically produced) Hg consumption and a complete nitrate or nitrite reduction (mainly to NH4+). This caused a slightly enhanced metal oxidation. In the case of stainless steel, corrosion caused by denitrifying microorganisms was evidenced by data on nitrate/nitrite ions and solubilized iron. Experiments with increasing nitrite concentrations indicated that nitrite in the range of 50 mg of NO2- -N/L inhibited the corrosion processes. Moreover, at concentrations above 140 mg NO2- -N/L, a significant production of nitric oxide (NO) was detected. Differences between iron and stainless steel powder at low concentrations of nitrate or nitrite are most probably due to differences in kinetics: metallic iron exhibited faster chemical than biological reactions as opposed to stainless steel. It is postulated that the inhibitory effect of higher nitrite concentrations could partly be due to the chemical formation of NO and its toxic effect on the microorganisms acting at the steel surface.

Assessing denitrification in groundwater using natural gradient tracer tests with 15N: In situ measurement of a sequential multistep reaction

Abstract: [1] Denitrification was measured within a nitrate-contaminated aquifer on Cape Cod, Massachusetts, using natural gradient tracer tests with 15N nitrate. The aquifer contained zones of relatively high concentrations of nitrite (up to 77 μM) and nitrous oxide (up to 143 μM) and has been the site of previous studies examining ground water denitrification using the acetylene block technique. Small-scale (15–24 m travel distance) tracer tests were conducted by injecting 15N nitrate and bromide as tracers into a depth interval that contained nitrate, nitrite, nitrous oxide, and excess nitrogen gas. The timing of the bromide breakthrough curves at down-gradient wells matched peaks in 15N abundance above background for nitrate, nitrite, nitrous oxide, and nitrogen gas after more than 40 days of travel. Results were simulated with a one-dimensional transport model using linked reaction kinetics for the individual steps of the denitrification reaction pathway. It was necessary to include within the model spatial variations in background concentrations of all nitrogen oxide species. The model indicated that nitrite production (0.036–0.047 μmol N (L aquifer)−1 d−1) was faster than the subsequent denitrification steps (0.013–0.016 μmol N (L aquifer)−1 d−1 for nitrous oxide and 0.013–0.020 μmol N (L aquifer)−1 d−1 for nitrogen gas) and that the total rate of reaction was slower than indicated by both acetylene block tracer tests and laboratory incubations. The rate of nitrate removal by denitrification was much slower than the rate of transport, indicating that nitrate would migrate several kilometers down-gradient before being completely consumed.