Showing papers on "Nitrite published in 1969"

Studies of nitrate reductase in marine phytoplankton1

Abstract: Certain marine phytoplankton contain the enzyme nitrate reductase when growing on nitrate, but only low levels of enzyme were found during growth with ammonium or when the nitrogen source was depleted. Netted samples of oceanic phytoplankton contained the enzyme when taken from waters with nitrate concentrations 2–10 µm. Ammonium was assimilated in preference to nitrate in phytoplankton cultures supplied with both forms of nitrogen at 5–15 µm. Enzyme synthesis and nitrate use began when ammonium was depleted to 0.5–1.0 µm. Nitrate reductase assay of phytoplankton samples is a useful tool in that a positive result indicates utilization of nitrate and a negative one implies growth on ammonium, nitrogen depletion, or, improbably, growth with other N-sources such as nitrite, urea, or amino acids. The enzyme assay seems especially useful for studying the timecourse of phytoplankton blooms because it provides a sensitive measure of the initiation and cessation of nitrate assimilation.

Nitrogen Metabolism of Lemna minor. II. Enzymes of Nitrate Assimilation and Some Aspects of Their Regulation

Abstract: In L. minor grown in sterile culture, the primary enzymes of nitrate assimilation, nitrate reductase (NR), nitrite reductase (NiR) and glutamate dehydrogenase (GDH) change in response to nitrogen source. NR and NiR levels are low when grown on amino acids (hydrolyzed casein) or ammonia; both enzymes are rapidly induced on addition of nitrate, while addition of nitrite induces NiR only. Ammonia represses the nitrate induced synthesis of both NR and NiR. NADH dependent GDH activity is low when grown on amino acids and high when grown on nitrate or ammonia, but the activities of NADPH dependent GDH and Alanine dehydro-genase (AIDH) are much less affected by nitrogen source. NADH-GDH and AIDH are induced by ammonia, and it is suggested that these enzymes are involved in primary nitrogen assimilation.

Factors affecting chemical transformations of nitrite in soils

Abstract: Tracer studies using 15N-enriched nitrite showed that soil pH and organic matter content are the key factors in nitrite decomposition and fixation of nitrite N in soils. The extent of nitrite decomposition and fixation of nitrite N was inversely related to soil pH. With soils having pH values between 5 and 7, the amount of nitrite N fixed and the amount volatilized at a given pH increased with increase in soil organic matter content; with soils having pH values less than 5, the amount of nitrite N fixed increased, and the amount of nitrite N volatilized decreased, with increase in soil organic matter content. Air-drying of soils treated with nitrite promoted nitrite decomposition, but did not markedly affect fixation of nitrite nitrogen. The amount of nitrite decomposed and the amount of nitrite N fixed on incubation of soils treated with nitrite increased with increase in nitrite level and in time and temperature of incubation. Increase in soil moisture content above a certain level decreased the amount of nitrite N volatilized during incubation of nitrite-treated soils, but did not markedly affect the amount of nitrite N fixed. Sterilization of soil before treatment with nitrite had little effect on nitrite decomposition or fixation of nitrite nitrogen. Nitrite decomposition and fixation of nitrite N occurred readily under conditions commonly encountered in the field.

Changes in nitrate and nitrate reductase levels on restoration of molybdenum to molybdenum-deficient plants

Abstract: The effect of molybdenum on nitrate reductase was assessed by incubating wheat leaf fragments with potassium nitrate, with or without molybdenum, under lights supplying 2000 f.c. Enzyme activity was then estimated by measuring the nitrite produced by the fragments and released into the solution during 1 hr in total darkness. Light stimulated the induction of nitrate-reducing activity while darkness was essential to obtain accumulation of nitrite. Molybdenum deficiency in wheat depressed nitrate reductase activity and dry matter yield. Molybdenum caused a rapid increase in nitrate reductase in tissue from deficient plants but had no such effect on tissue from non-deficient plants. The difference in response patterns between deficient and non-deficient plants, induced by molybdenum treatment could form the basis for a plant test for molybdenum deficiency.

The biochemistry of nitrifying microorganisms.

Abstract: SUMMARY 1Biological nitrification is mediated primarily by two genera of bacteria, Nitrosomonas and its marine form Nitrosocystis, oxidizing ammonia to nitrite, and Nitrobacter, converting nitrite into nitrate. These are chemoautotrophic organisms since they usually derive their energy for growth by oxidizing these inorganic nitrogen compounds and their carbon from carbon dioxide, carbonates or bicarbonates. 2The morphology and structure of these Gram-negative bacteria studied by electron microscopy show numerous intracellular membranes reminiscent of those in photosynthetic bacteria and blue-green algae. These structures may therefore be associated with the production of ATP. 3The bacteria are difficult to grow in pure cultures in sufficient amounts for biochemical work since their generation time is around 10 hr. and the yields are only about one hundredth of those obtained with heterotrophic bacteria. Thus in continuous cultures great care must be taken to avoid ‘wash-out’ of the cells. Since Nitrosomonas and Nitrosocystis produce copious amounts of nitrous acid, which would eventually retard growth, pH stat units are used to titrate the cultures continuously with a solution of sodium carbonate, to hold the pH around 7–8. 4The respiratory chain which is associated with cell membranes, contains flavin, quinones and many cytochromes linking to oxygen as a terminal acceptor. In Nitro-somonas-Nitrosocytis hydroxylamine is oxidized by the electron transfer chain and in Nitrobacter nitrous acid is utilized. The ammonia-oxidizing system, which in Nitrosomonas probably resides near the cell surface, does not appear to survive cell breakage. During the oxidation of hydroxylamine and nitrous acid by the respiratory chains, a phosphorylation occurs but the P/O ratios around 0–30 are low. There is little energy reserve material in the cells, possibly β-hydroxybutyrate and some metaphosphates and as soon as the oxidative processes are impaired the cells cease dividing. 5Chemoautotrophic bacteria have a novel way of producing reduced nicotinamide adenine dinucleotide (NADH). This involves a reversal of electron flow from reduced cytochrome c to nicotinamide adenine dinucleotide (NAD) that is energy-dependent, thus requiring adenosine triphosphate. 6Reductase enzymes, nitrate, nitrite and hydroxylamine reductases in Nitrobacter and nitrite and hydroxylamine reductases in Nitrosomonas, have been described. They appear to be readily extracted in soluble form and are probably assimilatory enzymes since 16N labelled nitrate, nitrite and hydroxylamine respectively in Nitrobacter and the last two in Nitrosomonas are readily incorporated into cell nitrogen. It has been suggested that a particulate nitrate reductase in Nitrobacter is coupled to the synthesis of adenosine triphosphate but adequate experimental evidence for this concept has not been produced. 7Some recent observations with Nitrobacter suggest that it grows on acetate, deriving all its energy and carbon skeletons from this source but the mean generation time for the bacterium is unchanged. Under these conditions the carbon dioxide fixing enzymes of the pentose pathway are suppressed. This then is a case of facultative chemoautotrophy but there is no increase in the biosynthesis of the TCA enzymes. Whether this is a widespread phenomenon in other chemoautotrophic bacteria remains to be established. If this does prove to be the case it would aid their survival in a variety of habitats and extend their distribution in soils and seas. 8The carbon dioxide fixing enzymes of the pentose pathway are found in the soluble parts of the cells. The major route is via the carboxydismutase system with only a small incorporation via the phosphoenolpyruvate carboxylase enzyme. Enzymes of the tricarboxylic acid cycle have low activities compared with those in heterotrophs and this overall slow metabolism, rather than the lack of a specific enzyme such as NADH oxidase, may well account for the slow growth of these bacteria. Although there is very active glutamic dehydrogenase in Nitrosomonas that utilizes ammonia, the enzyme has a very small activity in Nitrobacter. This poses a problem of the route of incorporation of nitrite nitrogen into cell nitrogen in the latter bacterium. 9A few heterotrophic fungi have been described which oxidize ammonia to nitrate but their activity is small compared with that of the nitrifying bacteria. 10It is concluded that the nitrifying bacteria which have many novel biochemical features not met with in other organisms merit further study.

Suppression by nitrate of enzymatic reduction of nitric oxide.

Abstract: SummaryWe found that the entire array of enzymes in Pseudomonas perjectomarinus that account for reduction of nitrate to nitrogen, including that which reduces nitrous oxide to nitrogen, was synthesized in 40, but not 35, min of incubation in a complete medium containing nitrate. Nitrite accumulated during the first 5-6 hr of culture despite the fact that we could demonstrate enzymes in crude cell-free extracts that reduced nitrite, nitric oxide, and nitrous oxide. To explain this, we found that nitrate suppressed the activity of nitric oxide reducing enzyme in crude extracts, as well as that in a fraction containing none of the other relevant reducing systems.

A comparison of the lethal effects of nitrite and hydroxylamine in the mouse

Abstract: Hydroxylamine hydrochloride injected i.p. is more acutely toxic to mice than sodium nitrite injected i.p.; but when given in equal sublethal doses, the two chemicals generate equivalent peak levels of methemoglobin. Peak levels of methemoglobin are reached in 10 min or less after hydroxylamine, and animals die within the same time period. Death is delayed after nitrite and correlates in time with the more delayed peak methemoglobin formation. A nitrite-generated methemoglobinemia persists longer than a hydroxylamine-generated methemoglobinemia both in mice and in mouse erythrocyte suspensions, but the effect of methylene blue in attenuating the methemoglobinemic response is more dramatic in the case of nitrite. Hydroxylamine further differs from nitrite in that the former has a greater tendency to produce "sulfhemoglobin-like" pigments. Pretreatment of mice with methylene blue significantly protects them against death by either nitrite or hydroxylamine and significantly attenuates the methemoglobinemic response to either chemical. These effects, however, are greater in the case of nitrite than in the case of hydroxylamine. l -Arginine does not alter significantly the methemoglobinemic response to hydroxylamine, and yet it protects mice against death by hydroxylamine but not by nitrite. These results are inconsistent with the interconversion of nitrite and hydroxylamine in mice or mouse red cells.

Determination of nitrite and nitrate in some horticultural and meat products and in samples of soil.

Abstract: This study of quantitative determination of nitrite and nitrate contents is based on spectrophotometric measurement of the red colour formed when sulphanilic acid is diazotised by the nitrite to be determined and coupled to 1-naphthylamine-7-sulphonic acid (Cleve's acid 1-7). Nitrate is first reduced to nitrite in a cadmium reducing column. Good results have been obtained with some horticultural and meat products and samples of soil.

Method of treating organic waste water

Abstract: A method of treating organic waste water which comprises the steps of bringing activated sludge consisting mainly of denitrifying bacteria into contact with organic waste water in the presence of nitrate ions or nitrite ions, keeping said waste water in an anaerobic state and destroying the decomposable organic matters contained in the waste water by virtue of the nitrate respiration of said denitrifying sludge.

Nitrate Reduction in Seawater of the Deep Nitrite Maximum off PERU1

Abstract: Nitrate-reducing bacteria were isolated from samples collected inside and outside the secondary nitrite maximum in oxygen-poor deep waters off the coast of Peru. Under anaerobic conditions at 20C in the laboratory, these bacteria reduced nitrate to nitrite in seawater enriched with 0.5 to 1.0 mg glucose/liter. Nitrate reduction also occurred in seawater supplemented only with 20 ,ug-atom Nose-N/liter and trace metals. Nitrite production generally was greatest during the first 24 hr while cell numbers were increasing. On continued incubation cells died, nitrate increased, and nitrite decreased. Dissolved organic carbon increased concurrently with the death of bacteria, indicating release of cell contents into the medium by lysis. Microbiological evidence is presented to show that the high nitrite concentrations in oxygen-poor deep waters of the secondary nitrite maximum arise from nitrate reduction,

The effect of light on nitrate and nitrite assimilation by chlorella and ankistrodesmus.

Abstract: Light stimulates the assimilation of nitrate and nitrite by two green algae, Chlorella pyrenoidosa and Ankistrodesmus braunii. Assimilation can be observed when the algae are illuminated in the absence of carbon dioxide under both aerobic and anaerobic conditions. The rates of assimilation by Chlorella do not depend on the presence of carbon dioxide, but Ankistrodesmus assimilates nitrate and nitrite more rapidly when cultures are illuminated in the presence of carbon dioxide than in its absence. The ratios of O2: NO3′ and O2: NO2′ vary from one experiment to the other and, with the exception of Chlorella cultures reducing nitrite they are higher than the ‘expected’ values of 2.0 and 1.5 respectively. Oxygen evolution accompanying nitrate and nitrite by algae illuminated in the absence of carbon dioxide is completely inhibited by DCMU at concentrations of 4 × 10-6 M. However, nitrite assimilation by both Ankistrodesmus and Chlorella and nitrate assimilation by Ankistrodesmus are less sensitive to the inhibitor.

Nitrite oxidase and nitrate reductase in Nitrobacter agilis

Abstract: Nitrite oxidase and nitrate reductase in Nitrobacter agilis were shown to be separate enzymes. The best separation of the two systems was achieved by ammonium sulphate fractionation. The effects of various compounds, including antimycin A, 2-n-heptyl-4-hydroxyquinoline N-oxide and chlorate, also clearly distinguish between the two enzyme reactions. The relationship between the two opposing reactions in Nitrobacter is discussed.

Factors influencing the colorimetric determination of nitrite with Cleve's acid

Abstract: The determination of nitrite with Cleve's acid has been investigated; the influence of composition of reagents and several experimental conditions have been evaluated. It is shown that provided the standards used to prepare the calibration graph and samples are treated in a similar way, then the choice of conditions may largely be left to the operator. A recommended procedure is given.

C‐Nitroso compounds: Part. XI. Trans‐azodioxycyclohexane (dimeric nitrosocyclohexane) by photochemical nitrosation of cyclohexane with alkyl nitrites

Abstract: The photonitrosation of cyclohexane by tertiary butyl nitrite has been studied as a model system for the photochemical reaction between alkyl nitrites and hydrocarbons. The products are trans-azodioxycyclohexane (trans-dimeric nitrosocyclohexane) and a minor amount of cyclohexanone oxime, together in 81 % yield. Most of the trans-dimer is formed via the cis-dimer, which can be isolated at low temperature. It is shown that optimal conditions for this reaction involve the use of a tertiary alkyl nitrite in low concentration, wavelengths around 400 nm and temperatures slightly below room temperature. The free radical mechanism of this reaction is supported by electron spin resonance spectroscopy.

Rapid changes in nitrite after gamma irradiation of fresh soils.

Abstract: Increases in nitrite in ten gamma-irradiated soils have been investigated under aerobic conditions up to 7 days after treatment over the range 0·25–2·5 Mrad. The formation of nitrite showed significant correlations with the percentage of soil inorganic carbon and incubation time, and over 100 ppm nitrite-N accumulated within 3 days in Broadmoor series, which contained the most inorganic carbon. Only the very acid series failed to produce nitrite, but formation and persistence was poor in all soils below pH 7. Leaching with ammonium or nitrate ions after irradiation suggested that microbial reduction of nitrate was the mechanism responsible for nitrite accumulation, rather than inhibition of nitrite oxidation.

Effect of chloride concentration on the decomposition of aqueous sodium nitrate by sunlight

Abstract: Rates and yields of nitrite formation in solutions, upon irradiation of aqueous sodium nitrate with ultraviolet light, are found to be consistently and considerably enhanced by their chloride content. The process is investigated under conditions met both, in the laboratory and under sunlight illumination, and the effects of altitude and temperature on the reaction studied in the field, are evaluated.

Determination of nitrate by reduction to nitrite

Abstract: pH約3で塩化アンモニウムの共存下で亜鉛粉末による硝酸の還元を行なえば,約80%の収率で亜硝酸に還元されることを知った.生成した亜硝酸をGR試薬で比色定量する.還元条件を検討した結果,pH(3.0～3.5),温度(0～20℃),還元時間(7～20分)などに幅があり,条件の設定が容易である.この点従来報告されている定量法よりすぐれていると思われる.硝酸,亜硝酸共存のときは,硝酸の検量線より硝酸と亜硝酸の合計濃度を求め,あらかじめ定量しておいた亜硝酸濃度を合計濃度から差し引いて硝酸濃度を求める.