Bacterial Nitrate Reduction Research Articles

An investigation of the levels ofN‐nitrosodimethylamine, apparent totalN‐nitroso compounds and nitrate in beer

Over 170 retail samples of beer have been analysed for N-nitrosodimethylamine (NDMA), apparent total N-nitroso compounds (ATNC) and nitrate. Levels of NDMA ranged from below 0.1 up to 1.2 micrograms/kg with a mean of 0.2 micrograms/kg. ATNC was detected in 42% of the samples in concentrations of up to 569 micrograms (N-NO)/kg. The levels of nitrate ranged from less than 0.2 up to 143 mg/kg with a mean of 16.8 mg/kg. There was no correlation between the amounts of NDMA and ATNC found in the retail beers. Samples taken during the course of fermentation showed that NDMA was unaffected by the bacterial reduction of nitrate which causes ATNC formation. HPLC studies using a photolysis/chemiluminescence detector revealed that the ATNC in beer are highly polar species of as yet unknown identity.

Estimation of Bacterial Nitrate Reduction Rates at In Situ Concentrations in Freshwater Sediments

A method was developed to follow bacterial nitrate reduction in freshwater sediments by using common high-performance liquid chromatographic equipment. The low detection limit (14 pmol) of the method enabled us to study concentration profiles and reaction kinetics under natural conditions. Significant nitrate concentrations (1 to 27 muM) were observed in the sediment of Lake Vechten during the nonstratified period; the concentration profiles showed a successive depletion of oxygen, nitrate, and sulfate with depth. The profiles were restricted to the upper 3 cm of the sediment which is rich in organics and loosely structured. Nitrate reduction in the sediment-water interface followed first-order reaction kinetics at in situ concentrations. Remarkably high potential nitrate-reducing activity was observed in the part of the sediment in which nitrate did not diffuse. This activity was also observed throughout the whole year. Estimates of K(m) varied between 17 and 100 muM and V(max) varied between 7.2 and 36 mumol cm day for samples taken at different depths. The diffusion coefficient of nitrate ([10 +/- 0.4] x 10 cm s) across the sediment-water interface was estimated by a constant-source technique and applied to a mathematical model to estimate the net nitrate reduction during the nonstratified period. In this period, observed nitrate reduction rates by the model, 0.2 to 0.4 mmol m day, were lower than those found for oxygen (27 mmol m day) and sulfate (0.4 mmol m day). During the summer stratification, nitrate was absent in the sediment and reduction could not be estimated by the model.

Influence of cysteine and nitrate on the endogenous formation of N-nitrosamino acids

The excretion of N-nitrosamino acids and nitrate in 24-h urine was studied over a continuous 45-day period for a single volunteer on supplemented diet regime. Days 1–10 (normal diet), 11–20 (normal diet + 600 mg nitrate/day), 21–25 (normal diet), 26–30 (normal diet + 200 mg L-cysteine/day), 31–35 (normal diet), 36–40 (normal diet + 600 mg nitrate + 200 mg l-cysteine/day) and days 41–45 (normal diet). The presence of N-nitrosohydroxyproline (NHPRO) in human urine is reported for the first time as well as the influence of l-cysteine on the formation of N-nitrosothiazolidine-4-carboxylic acid (NTCA) and N-nitroso-2-methylthiazolidine-4-carboxylic acid (NMTCA) under a normal nitrate burden (75 mg/day) and a high nitrate burden (675 mg/day). After estimation of the amount of dietary nitrite consumed and the extent of nitrite formation by bacterial reduction of nitrate in the oral cavity, the total daily exposure to nitrite was calculated. From a total daily exposure of 7.2 mg nitrite/day from a typical European diet, 0.08% is required for the endogenous formation of N-nitrosamino acids found in urine. Under an increased nitrate burden (675 mg/day), the total exposure to nitrite was increased to 38 mg/day of which 0.14% was required for the endogenous formation on N-nitrosamino acids.

The nitrogen cycle of an East Coast, U.K. saltmarsh: II. Nitrogen fixation, nitrification, denitrification, tidal exchange

Measurements of nitrogen fixation (acetylene reduction) showed greatest rates in the saltmarsh pans with a benthic layer of cyanobacteria present. The smallest amount of nitrogen fixation occurred on the marsh surface where a Puccinellia maritima/Halimione portulacoides plant association shaded the underlying sediment. Phototrophic nitrogen fixation was always greater than dark, chemotrophic, bacterial fixation. Only a small proportion of the total amount of ammonium, which was formed during detrital breakdown, was nitrified to nitrate. Although there is a high capacity for bacterial nitrate reduction in these sediments, the process is limited by low nitrate availability and most nitrate upon reduction is converted to ammonium rather than being denitrified to gaseous products. Denitrification does not, therefore, result in any great loss of nitrogen from the saltmarsh. There was little net import or export of nitrogen on an annual basis, although nitrate and organic-N in small particulate material was removed from tidal water by the marsh, and there was net annual export of ammonium, dissolved organic-N and organic-N in large particulate material. Losses of nitrogen by the small net tidal export and by denitrification were approximately balanced by nitrogen fixation. It was concluded that the nitrogen cycle of the Colne Point saltmarsh was balanced on an annual basis, with most nitrogen being recycled within the marsh. The saltmarsh did not apparently act as a net source of nitrogen for the adjacent estuary, although it may act as an important processor of nitrogen, removing some forms of nitrogen such as nitrate from tidal water while exporting other forms of nitrogen such as dissolved organic-N.

Modifiers of endogenous nitrosamine synthesis and metabolism.

N-Nitroso compounds (NOCs), a class of versatile carcinogens (1,13), are formed in nature, most likely since mankind first existed on earth, whenever nitrosating agents such as nitrite or nitrosating gases encounter nitrosatable amines. To date, more than 300 NOCs have been tested in animals, and about 90% of them produced tumors in 40 animal species, including primates. Humans are exposed to NOCs from exogenous and endogenous sources through nitrosation of ingested/inhaled amino precursors. Nitrite is produced by bacterial reduction of nitrate, normally in the mouth, and the nitrosation reaction generally proceeds through an acid-catalyzed reaction in the stomach. Any nitrosation reaction occurring in vivo is, however, affected by many factors, such as the pH, precursor concentration, and the presence of catalysts and inhibitors. These various factors, some of which are difficult to measure in vivo, have complicated the estimation of nitrosation reactions occurring in humans.KeywordsEsophageal CancerExtrahepatic TissueBetel QuidBeetroot JuiceEndogenous FormationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Denitrification and Bacterial Numbers in Riparian Soils of a Wyoming Mountain Watershed

Denitrification and Bacterial Numbers in Riparian Soils of a Wyoming Mountain Watershed

Bacterial reduction of trimethylamine oxide.

Trimethylamine oxide, which is found in relatively high concentrations in the tissues of marine animals, serves as an electron acceptor in the anaerobic metabolism of a number of bacteria associated primarily with three environments: the marine environment (e.g. Alteromonas and Vibrio), the brackish pond (nonsulfur photosynthetic bacteria), and animal intestines (Enterobacteriaceae). Its reduction to trimethylamine by such bacteria can constitute a major spoilage reaction during the storage of marine fish. In the Enterobacteriaceae, anaerobic respiration with TMAO has been shown to support oxidative phosphorylation. Electron transport to TMAO in these bacteria involves flavin nucleotides, menaquinones, both b- and c-type cytochromes, and a molybdoenzyme reductase. Formate, hydrogen, lactate, and glycerol all serve as electron donors for TMAO respiration. Electrophoretically distinct constitutive and TMAO-induced reductases are synthesized by both E. coli and S. typhimurium. Electron transport to TMAO is repressed both by air and by nitrate. A number of genes involved in TMAO respiration have been mapped, but the structural gene for the inducible TMAO reductase has not yet been firmly established. Oxidative phosphorylation is also supported by TMAO reduction in Alteromonas. In this organism, which is nonfermentative, TMAO respiration resembles aerobic respiration in that intermediates of the TCA cycle are excellent electron donors. Alteromonas exhibits a requirement for NaCl for growth on TMAO and certain electron donors. As in the Enterobacteriaceae, air and nitrate both interfere with TMAO reduction. The role of TMAO reduction in the anaerobic metabolism of nonsulfur purple bacteria has not yet been resolved; it is not clear if TMAO serves simply as an accessory oxidant for fermentation or if TMAO reduction is associated with energy-yielding membrane-bound electron transport. Some of the confusion regarding this bacterial group stems from the fact that much of the work to date has involved parallel studies of TMAO and dimethyl sulfoxide reduction, and it is not yet known whether the two compounds are reduced by the same enzyme. Although our understanding of bacterial TMAO reduction lags far behind our knowledge of bacterial nitrate reduction, it is unlikely that this will always be the case.(ABSTRACT TRUNCATED AT 400 WORDS)

Review: putative mutagens and carcinogens in foods. I. Nitrate/nitrite ingestion and gastric cancer mortality.

Published figures for per capita daily levels of nitrate ingestion in the 1970s are compared with gastric cancer mortality estimates for the same period. A strong positive correlation is observed in 12 countries, not only when the data are analyzed as a linear-linear function, as illustrated in this paper, but also when the relationship is analyzed as a function of (nitrate)2. This correlation supports the concept that important components of gastric cancer induction are the in vivo bacterial reduction of nitrate to nitrite and the intragastric formation of mutagenic/carcinogenic nitroso, and possibly nitro compounds. Data are summarized from a recent National Academy of Sciences [1981] study that enumerates by individual dietary sources the mean ingestion of nitrate and nitrite by the United States population at the present time. The ingestion figures are used to calculate the probable current gastric nitrite load in US adults with normal gastric acidity. Similar calculations are provided for past years (1925, 1936-1937, and 1971-1972). Since 1925, there has been an approximately threefold decrease in gastric cancer mortality in the US, and this decline is paralleled by an approximately fourfold decrease in average gastric nitrite load. The excessive ingestion of nitrate/nitrite in the US in past years is attributed to the very high content of nitrate and nitrite in cured meats. Several ways compatible with current US farming and marketing practices that are capable of reducing the gastric nitrite load even further are pointed out.

Exchange of nitrate, and the products of bacterial nitrate reduction, between seawater and sediment from a U.K. saltmarsh

The ability of bacteria in saltmarsh sediment to reduce nitrate was investigated using sediment cores in continuous flow laboratory systems. Solutions containing varying concentrations of nitrate were allowed to attain steady states with respect to exchange of nitrate, ammonium and nitrite between the water and sediment. The sediment had both a high affinity for nitrate and a large capacity to remove nitrate from the overlying water ( K NO 3 0.319±0.114 mmol NO 3 − 1 −1 : V max 12.89±2.11 mmol NO 3 − m −2 h −1 ). Ammonium and nitrite in the effuent from each core represented only a small proportion of the total nitrate removed, the largest part disappearing from the system, presumably by denitrification within the sediment.

Hydrographic features of the deep water of the Bering Sea—the sea of Silica

The deep water of the Bering Sea contains concentrations of dissolved silicate up to 240 μg at. Sil −1. Nitrate concentrations are less than in the North Pacific at the depths with the same oxygen contents. The rates of chemical and biochemical reactions occurring in the deep water (below 2km) were estimated from hydrographic data by applying a modified one-dimensional model. Oxidation of organic matter in the oxygenated water column of the Bering Sea was twice that of the North Pacific. Silicate regeneration, or dissolution of biogenic opal and denitrification, or bacterial nitrate reduction to gaseous nitrogen, on and in the bottom sediments of the deep Bering Sea basin were calculated to be 212 and 20 mg at.m −2 yr −1, respectively. These values are consistent with the ones estimated from vertical profiles of dissolved silicate and nitrate in the interstitial water of the sediments. The chemical anomaly observed in deep water of the Bering Sea can be produced by these reactions in the bottom sediments. The decomposition of organic matter in anoxic sediments accounts for about 8% of the total organic matter decomposing in the water column below 2km and in the sediments.

Gastric Cancer in Colombia IV. Nitrite and Other Ions in Gastric Contents of Residents From a High-Risk Region<xref ref-type="fn" rid="FN1">2</xref>

Samples of gastric contents from 2 groups of patients from a region of high risk for gastric cancer were analyzed for pH, nitrite, nitrate, thiocyanate, and chloride. In each group, the patients could be divided into 2 subgroups: those with a gastric pH of less than 5 and those with a gastric pH of greater than 5. Above pH 5, nitrite was correlated with nitrate. The pH greater than 5 subgroups had significantly higher (P less than 0.01) nitrite content (20- to 100-fold). Some high- and low-nitrite samples were also analyzed for macro and trace metal ions, but differences were not significant. This is the first report in which patients with diagnosed gastric pathology related to a precancerous state were shown to have high levels of a putative carcinogen precursor. The results were compatible with our original hypothesis of intragastric nitrite formation by bacterial reduction of nitrate and concomitant synthesis of carcinogenic N-nitroso compounds.

A steady-state model for sulphur isotope fractionation in bacterial reduction processes

A model is developed to explain the isotope fractionation effects produced in laboratory experiments involving the reduction of sulphate to hydrogen sulphide by the bacterium Desulfovibrio desulfuricans. The approach differs from previous ones in its use of zero-order kinetics to describe the uptake of sulphate by the bacterium. Expressions are developed which relate the overall isotope effects produced by the bacterium to the ratios of backward to forward flows between its internal sulphur reservoirs. Other applications of this type of model are discussed, including the differences of isotopic composition between sulphate and hydrogen sulphide in the Black Sea and an unusual isotope effect observed in the course of bacterial nitrate reduction.

Ökologische Untersuchungen über nitratreduzierende Bakterien im Wasser des Plußsees (Schleswig‐Holstein)

Nitrate reducing bacteria are always available in the water of the Pluß‐See. Their number varies from 10 to 2000 cells/ml. The denitrifying bacteria with only 0 to 50 cells/ml are less represented, but under favourable conditions, e. g. high nitrate supply, lack of oxygen, an enrichment of these microorganisms is possible. The influence of oxygen, nitrate, nitrite, and ammonium concentration on the activity of the nitrate reducing bacteria was examined. In the summer months, cell number and activity are correlated. During the winter, a correlation does not exist, although high cell numbers and activities are also found. It is likely that oxygen and the relatively low nitrate value repress the nitrate reduction. Between activity and the presence of nitrite no relation has been found. From the course of the nitrate and nitrite curves (0–650 μg N‐NO/l, and 0–100 μg N‐NO/l, reap.) and from the cell‐numbers and activities we can make the conclusion that, at least for the summer months, a bacterial nitrate reduction in the oxygen free zone has occurred. The presence of ammonium ions in the water of the Pluß‐See (50–3000 μg N‐NO/l,) could probably influence the activity.

Reversal of Nitrate Inhibition of Nodulation by Indolyl-3-acetic Acid

NITRATE appears to have an influence on the action of indolyl-3-acetic acid (IAA) in the initiation and development of the symbiosis between legumes and bacteria of the genus Rhizobium. For example, it is often suggested that IAA is responsible for the curling of root hairs that is taken to be a prelude to the bacterial invasion of the legume root1, and Thornton2 noted that the percentage of lucerne root hairs that were deformed in the presence of Rhizobium meliloti culture filtrates was reduced if the plants were simultaneously supplied with NaNO3. IAA is likewise proposed to be involved in the nodulation process itself3, the nodule biogenesis likewise being repressed by nitrate. Recently, Tanner and Anderson4 suggested that the inhibition may be attributable to a destruction of auxin by the nitrite produced from the bacterial reduction of nitrate. In this communication, it is demonstrated that not only may nitrate influence the lAA-induced changes but also that IAA may, conversely, mitigate the inhibition of nodulation by nitrate.

Occurrence of hydroxylamine in lake waters as an intermediate in bacterial reduction of nitrate.

THE occurrence of hydroxylamine as an intermediate of the enzymatic reduction NO3− → NH3 or oxidation NH3 → NO3− has recently interested many biochemists1. Thus certain authors have been able to confirm the formation of this compound in the process of the oxidation or reduction of nitrogen compounds2,3.

British Food Journal Volume 42 Issue 9 1940

British Food Journal Volume 42 Issue 9 1940