NOB are responsible for the second step of nitrification oxidizing nitrite to nitrate and have three key impacts on aquatic habitats. First, they are responsible for the formation of nitrate, which provides a critical nitrogen source for microbial and plant assimilation. Second, they provide a substrate for denitrification, which results in the formation of gaseous dinitrogen for evolution out of the aquatic habitat.
Third, they reduce nitrite toxicity to fish and other aquatic organisms and indirectly reduce ammonia toxicity by consuming the end-product of microbial ammonia oxidation. If nitrite oxidation rates are reduced or halted due to environmental perturbation, nitrite concentrations will increase and negative effects, such as toxicity, hypoxia, and loss of biodiversity, may propagate through the ecosystem.
Nitrobacter and Nitrospira are often identified as the primary NOB present in freshwater systems Hovanec et al. Sequences from the recently discovered Candidatus Nitrotoga Alawi et al. The relationship between Ca. Nitrotoga relative abundance, nitrite oxidation rates, and in situ nitrite concentrations remains understudied. Despite the detection of Ca. Nitrotoga gene sequences in a variety of freshwater habitats, little is known about the physiological potential of these organisms or their response to changing environmental conditions.
Across the entire genus, physiology data have only been reported for a small number of Ca. Nitrotoga cultures, which were enriched from permafrost, activated sludge, an aquaculture system, and coastal sand Alawi et al. These physiological studies have indicated that optimal temperatures for Ca. Nitrotoga has been cultured at pH values ranging from 6. There are no prior reports on the physiology of freshwater Ca. Nitrotoga so it is unknown whether or not these NOB have similar activity to Ca.
Nitrotoga enriched from other habitats. Here, we determine the physiology of a newly identified Ca. Nitrotoga species from a natural freshwater system, Ca. CP45 Boddicker and Mosier, We explore the CP45 genome to make predictions about which genes may be involved in the physiological responses that were observed.
Physiology and genomic potential of Ca. CP45 is directly relevant to Colorado ecosystems, but can also be viewed as more broadly applicable to other freshwater systems since CP45 is closely related to other freshwater Ca.
Determining the physiological limits of the newly described Ca. The cultures were enriched with NOB from the Ca. Nitrotoga genus based on PCR and amplicon sequencing; Ca. The Ca. CP45 genome was previously sequenced and annotated Boddicker and Mosier, Genome sequence and phylogenetic analyses showed that the NOB in the culture represented a new species within the Ca. Nitrotoga genus Boddicker and Mosier, Here, further annotation of genes specific to processes described in this study was conducted using the eggNOG database and mapper Huerta-Cepas et al.
NOB activity in culture is commonly measured by following rates of substrate nitrite utilization or product nitrate formation Prosser, Here, cultures were regularly monitored for nitrite utilization using a Griess nitrite color reagent composed of 10 g sulfanilamide SULF , 1. Griess nitrite color reagent was mixed with culture samples at a ratio.
Nitrite concentrations present in sampled media were calculated using resultant end point absorbance readings and associated nitrite standards 0—0. In all, more than 10, individual nitrite measurements were made for the experiments described below. Nitrite was measured from subsamples collected approximately every 6 h. At select time points, 10 ml of each culture was filtered through 0. DNA was extracted as previously described Boddicker and Mosier, Nitrite concentrations were measured as described above.
NOx concentrations were calculated using resultant end point absorbance readings and associated standards 0—0. Nitrate was determined by subtracting nitrite values from the NOx values. The qPCR was run with three technical replicates from each time point. Melt curve analysis was performed after each run with plate reads at a temperature increment of 0.
All physiology treatments utilized FNOM with a final concentration of 0. Prior to use, all scintillation vials were soaked in 1. The inoculum culture was regularly monitored for nitrite oxidation activity. Immediately after depletion of nitrite, Ca. Triplicate cultures were inoculated for each experimental condition and grown under aerobic conditions. Therefore, data should be compared within an experiment, but not necessarily between experiments e.
For antibiotic treatments, solutions of erythromycin, penicillin penicillin G , sulfamethoxazole, and trimethoprim were made at concentrations of 5, 50, and nM in a base of FNOM. All vials were incubated in the dark with the exception of the light treatment.
Nitrite oxidation rates were calculated across three time points within the period of logarithmic nitrite consumption for each vial sampled. Individual rates were calculated for each replicate and then averaged.
Three sampling sites were selected along the South Platte River Basin to evaluate nitrite oxidation capabilities of the endogenous microbial communities upon exposure to antibiotics. Each site was chosen due to contrasting landscape use and water chemistry Storteboom et al. Surface sediment samples were obtained from each site and immediately placed on ice for processing at the lab within a few hours. Three sediment samples from each location were physically homogenized and 1.
Antibiotics were chosen based on their presence in river waterways as well as their antibacterial properties and pharmacokinetics. Biological controls contained river sediment and FNOM with no antibiotics. Blank controls contained FNOM and sediment samples 1. Water column mesocosm experiments were set up utilizing the same three predetermined sites.
For each site, ml of surface water from three separate grab-bottle captures were placed into a sterile, acid-washed Nalgene and mixed for homogenization. Homogenized site water was amended with nitrite 0. Biological controls contained river water amended with nitrite, but with no antibiotics.
Blank control water samples 45 ml were sterilized by first filtering the sample with a 0. Nitrite concentrations and nitrite oxidation potential rates were determined as described above. Environmental parameters were measured at the river site where the Ca.
CP45 culture inoculum was collected see above. Briefly, surface water parameters were measured approximately every 4—8 weeks from May to July Water quality data were obtained from the Northern Water Conservancy District Northern Water Conservancy District, at a site 2 miles downstream from the CP45 sampling site latitude Data included water temperature, pH, turbidity, and dissolved inorganic nitrogen concentrations.
At a sampling site 9 miles upstream from CP45 latitude We previously enriched Ca. Genomic sequencing revealed the metabolic potential to couple the oxidation of nitrite with aerobic respiration for energy conservation via a novel nitrite oxidoreductase enzyme Boddicker and Mosier, Nitrotoga-like sequences found in freshwater habitats across the globe Boddicker and Mosier, As a representative freshwater Ca.
CP45 to oxidize nitrite under a range of chemical and physical conditions to better understand how these NOB might respond in varying habitats across the river system. The South Platte River flows across the Colorado Front Range where multiple land-use types result in fluctuating contaminant inputs, including urban WWTP discharge, agricultural land-use areas with concentrated fertilizer and pesticide application, and land areas with a high density of animal feed operations Storteboom et al.
Pristine headwaters in the Rocky Mountains near central Colorado migrate through a gradient of human activities, from urban sites in the Denver metropolitan area, to mixed setting sites dominated by urban and agricultural land use, to the most northern sites dominated by predominantly agricultural land use Dennehy et al. Batch cultures of Ca. CP45 grown in media with 0. Maximum 16S rRNA gene copies at 69 h post-inoculation coincided with a logarithmic decline in nitrite concentrations, followed by a tapering off once nitrite was depleted Figure 1.
Accounting for genomic estimates showing that the C a. CP45 oxidized NO 2 - at concentrations ranging from 0. Figure 1. Nitrite oxidation in the Ca. CP45 enrichment culture coupled with increased concentrations of nitrate and copies of Ca. Nitrotoga 16S rRNA genes. If not visible, error bars are smaller than data points. Though some NOB are inhibited by ammonia e. Specifically, some species of Ca. Nitrotoga have demonstrated stimulated nitrite oxidation with the addition of 0.
Here, Ca. CP45 oxidized 0. These concentrations were higher than in situ river water ammonium concentrations at the CP45 sampling site Supplementary Figure 1 , suggesting that water column ammonium does not interfere with the potential for riverine nitrite oxidation.
Prior genomic analyses indicated that CP45 encodes an ammonium transporter amtB potentially facilitating ammonium assimilation Boddicker and Mosier, Further research should evaluate how inorganic nitrogen concentrations impact the ecology of Ca. CP45, including resource partitioning with other co-occurring NOB depending on enzyme kinetics and the range of substrate concentrations.
Microorganisms in aquatic environments are exposed to light at varying intensities given fluctuating depths and water transparency; however, no prior studies have evaluated the effect of light exposure on Ca. To test photosensitivity, Ca. Photoeffect on Ca. CP45 could be the result of photooxidation of c- type cytochromes, previously reported in Ca.
Nitrotoga genomes Boddicker and Mosier, ; Kitzinger et al. Cytochrome c has been shown to absorb light in the visible spectrum causing photodynamic destruction of amino acid residues Spikes and Livingston, , resulting in light-induced cell death Bock, ; Bock and Wagner, In some habitats, photochemical instability of nitrite Zafiriou and True, could result in photoinhibition by decreasing substrate availability, though that is unlikely in the experiments conducted here since nitrite concentrations were constant over time in the CP45 incubations and in the controls that contained no biomass.
Figure 2. Nitrite utilization by Ca. Photoinhibitory effects have been found to occur in several other nitrifying microbes Nitrosomonas , Nitrosococcus , Nitrospira , Nitrococcus , and Nitrobacter species Hooper and Terry, ; Yoshioka and Saijo, ; Vanzella et al. Photoinhibition documented in Ca.
CP45 may also impact other Ca. This trait likely impacts the environmental range of these organisms, with nitrite oxidation activity occurring primarily in habitats devoid of light. CP45 was enriched from a river water column that exhibits daily and seasonal fluctuations in light exposure in part dependent on the levels of suspended particulate and organic matter. Turbidity as a measure of water clarity near the CP45 river site ranged from 4 to NTU over time Supplementary Figure 2 , which spans the range of values typically seen in pristine streams and heavily sedimented rivers.
High water column turbidity levels may alleviate some of the photoinhibition for nitrite oxidation by Ca. CP45 within the water column. However, turbidity could have secondary effects on NOB related to increased water temperature as the suspended particles absorb more heat or reduce dissolved oxygen concentrations from decreased photosynthesis Austin et al. Nitrite was oxidized in Ca. CP45 cultures at pH 5. At the most acidic conditions tested pH 5. These results were consistent with prior Ca.
Nitrotoga physiology studies demonstrating near-neutral pH culture conditions and optima: Ca. Nitrotoga arctica cultivated at pH 7. AM1 cultivated at pH of 8. HW29 cultivated at pH 6. HAM-1 cultivated at pH 7. At the CP45 river enrichment site, the water pH ranged from 7. CP45 is likely able to perform nitrite oxidation at all pH levels measured within the river year-round.
It cannot be ruled out that pH changed over the course of the incubation; however, the media has some buffering capacity and NOB cultures typically become slightly more acidic over time due to proton production during nitrite oxidation Prosser, Other community members in the enrichment culture may have impacted these results see below ; however, no other NOB were identified in the 16S rRNA gene or genome sequence dataset and no other electron donors or accepters were added to the media.
Figure 3. Temperature and pH optima for the nitrite-oxidizing activity of Ca. A Mean nitrite oxidation rates during incubation at varying temperatures. B Mean nitrite oxidation rates during incubation at varying pH conditions. Decreased nitrite oxidation in Ca. CP45 cultures at decreased pH values is likely the result of a combination of factors associated with abiotic chemistry and bacterial physiology. According to the nitrous acid equilibrium, the concentration of nitrous acid increases as pH decreases, resulting in a corresponding decrease in the nitrite pool available for NOB energy generation Philips et al.
Nitrite oxidation has been shown to be inhibited at low pH due to the toxicity of nitrous acid Prosser, and references therein. Additionally, acidic pH conditions can be toxic to NOB cells by causing a disruption in the proton concentration that is intricately involved in cellular bioenergetics through the proton motive force Krulwich et al. Decreased pH has also been found to alter the catalytic activities of enzymes involved in nitrogen transformations by compromising their structural integrity Schreiber et al.
In non-neutral pH conditions, additional energy must be expended to combat pH stress, such as the expression of membrane pumps to actively uptake protons or the efflux of protons to maintain internal pH. Collectively, low nitrite pools and physiological stress at low pH can potentially lead to insufficient energy for growth Prosser, Nitrite oxidation at pH 5.
Takahashi et al. IOacid Hankinson and Schmidt, enriched from acid soils. We probed the Ca. CP45 genome for genes predicted to be involved in acid homeostasis. Another potential mechanism of acid tolerance is to regulate proton and cation transport in order to reduce the overall influx of protons into the cytoplasm under low pH conditions Booth, ; Baker-Austin and Dopson, The CP45 genome encoded a large number of inorganic ion transport proteins, including several cation:proton antiporters, cation-transporting ATPases P-type , and cation-related signal transduction proteins.
Similar to the acidophilic ammonia-oxidizing archaeon, Ca. Nitrosotalea devanaterra Lehtovirta-Morley et al. CP45 genome encoded two carbonic anhydrases that may have a dual function for carbon cycling and cytoplasmic buffering to prevent acidification Sachs et al. Intriguingly, this cultivation strategy resulted in the successful enrichment of two novel Nl.
This finding indicates that these NOB are more widely distributed than previously assumed, albeit at very low numbers. Therefore, the environmental distribution of these NOB seems not to be restricted to thermophilic conditions.
Fast and reproducible initial enrichment of Nitrolancea spp. In this study, a preference for a reduced oxygen supply Figure 3B of N. Accordingly, Nitrolancea -like sequences have been detected in a reactor treating synthetic low-strength wastewater at low dissolved oxygen contents Yu et al. The proliferation of the different Nitrolancea strains at nitrite concentrations between 3 and 40 and even 70 mM, respectively, matches the extremely high half-saturation constant K m for nitrite determined for Nl.
The K m of this strain was found to be 1 mM nitrite, which corresponds to the lowest substrate affinity of any NOB determined so far and is in line with the high substrate concentrations present in the bioreactor Nl. The Nitrolancea cultures investigated here revealed a higher affinity for nitrite, although there was a great variance between values for strain Z and only one measurement was done for Nl.
Nevertheless, our preliminary results suggest that the K m value of Nitrolancea is in the range of the different Nitrobacter species Nowka et al. Nevertheless, high substrate concentrations are necessary for optimal growth of Nitrolancea and nitrite was oxidized slowly when present in low concentrations Figures 4B,D.
Comparing the genomes and NxrA gene sequences from the different enrichments, it has become obvious that distinct representatives of Nitrolancea grew depending on the respective medium for instance 3 mM vs. The nxrA gene within the metagenome 40 of the culture E2 is non-operonal, whereas in close vicinity to the nxrA gene of the metagenome 35 a cytochrome c was found.
Therefore, the initial samples must have contained a microdiversity of Nitrolancea strains, which selectively proliferate once their special demands were met. Nitrolancea -like 16S rRNA gene sequences have only occasionally been detected in full-scale nitrifying activated sludge systems so far Speirs et al. The Nitrolancea -typical marker fatty acid methyl octadecanoic acid 12methyl Sorokin et al.
The abundance of methyl octadecanoic acid increased slightly to 0. However, similar glycolipids are also characteristic for other thermophilic Chloroflexi , like for instance Thermomicrobium , which has also been detected in WWTPs based on 16S rRNA gene sequences Spieck et al.
Therefore, it is still speculative if Nitrolancea also occurs in activated sludge, which was used as inoculum for the centrate reactor.
Elevated ammonium or nitrite concentrations could not be measured at the sampling sites, thus posing the question if alternative substrates might have enabled proliferation of Nitrolancea.
Some NOB are metabolically versatile and can use simple organic carbon compounds like formate, hydrogen, and even ammonia as additional energy sources Koch et al.
Furthermore, different NOB possess the genetic potential to use various sulfur compounds Starkenburg et al. The ability for cyanate degradation might provide an alternative source to generate ammonia for N-assimilation.
One of these strains represents a new species within the genus Nitrolancea. The strain is a mesophilic, aerobic, chemolithoautotrophic bacterium, which stoichiometrically converts nitrite to nitrate and uses carbon dioxide as carbon source.
Forms short rods with tapered ends; Gram-positive. Requires ammonium supplementation and tolerates high nitrite and ammonium concentrations. Strain availability will be performed upon request. AG performed the sampling. SH worked on the Nitrolancea enrichments.
SK did physiological experiments. DI performed genome sequencing. All authors read and agreed on the final manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. HSE is appreciated for the support in getting samples from Hamburg-Dradenau. Elke Woelken is acknowledged for excellent technical help in electron microscopy and Theo van Alen for sequencing.
Alawi, M. Cultivation of a novel cold-adapted nitrite oxidizing betaproteobacterium from the Siberian Arctic. ISME J. Amann, R. Fluorescent-oligonucleotide probing of whole cells for determinative, phylogenetic, and environmental studies in microbiology.
Phylogenetic identification and in situ detection of individual microbial cells without cultivation. Andrews, J. Google Scholar. Boddicker, A. Genomic profiling of four cultivated Candidatus Nitrotoga spp. Caporaso, J. QIIME allows analysis of high-throughput community sequencing data. Global patterns of 16S rRNA diversity at a depth of millions of sequences per sample. Chiacchiarini, P. First assessment of acidophilic microorganisms from geothermal Copahue-Caviahue system.
Hydrometallurgy , — Chiodini, G. Carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at Copahue-Caviahue volcanic complex Argentina. Courtens, E. Daims, H. Complete nitrification by Nitrospira bacteria. Nature , — Dowd, S. Survey of bacterial diversity in chronic wounds using pyrosequencing, DGGE, and full ribosome shotgun sequencing. BMC Microbiol. Edwards, T. FEMS Microbiol.
Ehrich, S. A new obligately chemolithoautotrophic, nitrite-oxidizing bacterium, Nitrospira moscoviensis sp. Elliott, D.
Niche partitioning of bacterial communities in biological crusts and soils under grasses, shrubs and trees in the Kalahari. Eren, A. PeerJ , e Fang, W. Biochemical pathways used by microorganisms to produce nitrous oxide emissions from soils fumigated with dimethyl disulfide or allyl isothiocyanate. Soil Biol. Friedman, L. Adaptability as the key to success for the ubiquitous marine nitrite oxidizer Nitrococcus. Giaveno, M. Physiologic versatility and growth flexibility as the main characteristics of a novel thermoacidophilic Acidianus strain isolated from Copahue geothermal area in Argentina.
Herlemann, D. Transitions in bacterial communities along the km salinity gradient of the Baltic Sea. Ishii, K. Enrichment and physiological characterization of a cold-adapted nitrite-oxidizing Nitrotoga sp. Kirstein, K. Close genetic relationship between Nitrobacter hamburgensis nitrite oxidoreductase and Escherichia coli nitrate reductases. Kitzinger, K. Koch, H. Microbial metabolism: Growth of nitrite-oxidizing bacteria by aerobic hydrogen oxidation. Science , — Expanded metabolic versatility of ubiquitous nitrite-oxidizing bacteria from the genus Nitrospira.
Kolmert, A. A fast and simple turbidimetric method for the determination of sulfate in sulfate-reducing bacterial cultures.
Koops, H. Brenner, N. Krieg, J. Staley, and G. Garrity, Boston, MA: Springer , — Effect of organic matter on growth and cell yield of ammonia-oxidizing bacteria.
Kruse, M. The nitrite-oxidizing community in activated sludge from a municipal wastewater treatment plant determined by fatty acid methyl ester-stable isotope probing. Kumar, S. Lebedeva, E. Moderately thermophilic nitrifying bacteria from a hot spring of the Baikal rift zone.
Isolation and characterization of a moderately thermophilic nitrite-oxidizing bacterium from a geothermal spring. Lee, I. OrthoANI: an improved algorithm and software for calculating average nucleotide identity.
Li, H. Minimap2: Pairwise alignment for nucleotide sequences. Bioinformatics 34, — Fast and accurate short read alignment with Burrows-Wheeler transform. Bioinformatics 25, — The genome of Nitrospina gracilis illuminates the metabolism and evolution of the major marine nitrite oxidizer. A Nitrospira metagenome illuminates the physiology and evolution of globally important nitrite-oxidizing bacteria.
Metagenomic analysis of nitrogen and methane cycling in the Arabian Sea oxygen minimum zone. PeerJ 4:e Manz, W. Phylogenetic oligodeoxynucleotide probes for the major subclasses of proteobacteria : problems and solutions.
Marks, C. Nitrospira -dominated biofilm within a thermal artesian spring: a case for nitrification-driven primary production in a geothermal setting. Geobiology 10, — Merodio, J. Argentina Mineral. Ngugi, D. Diversification and niche adaptations of Nitrospina -like bacteria in the polyextreme interfaces of Red Sea brines. Nikolenko, S. BayesHammer: Bayesian clustering for error correction in single-cell sequencing.
BMC Genomics S7. Notredame, C. T-coffee: A novel method for fast and accurate multiple sequence alignment. Nowka, B. Comparison of oxidation kinetics of nitrite-oxidizing bacteria: Nitrite availability as a key factor in niche differentiation.
Nurk, S. MetaSPAdes: A new versatile metagenomic assembler. Genome Res. Off, S. Enrichment and physiological characterization of a novel Nitrospira -like bacterium obtained from a marine sponge.
Orlando, J. Palomo, A. Comparative genomics sheds light on niche differentiation and the evolutionary history of comammox Nitrospira. Parks, D. A standardized bacterial taxonomy based on genome phylogeny substantially revises the tree of life. CheckM: Assessing the quality of microbial genomes recovered from isolates, single cells, and metagenomes. Respiratory detoxification of nitric oxide by the cytochrome c nitrite reductase of Escherichia coli. Hegesh, E. Blood nitrates and infantile methemoglobinemia.
Acta , — Reactive metabolites from N -nitrosamines. Tricker, A. Carcinogenic N -nitrosamines in the diet: occurrence, formation, mechanisms and carcinogenic potential. Calmels, S. Characterization of bacterial cytochrome cd 1-nitrite reductase as one enzyme responsible for catalysis of nitrosation of secondary amines.
Carcinogenesis 17 , — Licht, W. Use of ascorbic acid to inhibit nitrosation: kinetic and mass transfer considerations for an in vitro system. Carcinogenesis 9 , — Novel mechanism of nitrosative stress from dietary nitrate with relevance to gastro-oesophageal junction cancers. Carcinogenesis 24 , — Abdel Mohsen, M. Human bladder cancer, schistosomiasis, N -nitroso compounds and their precursors. Cancer 88 , — Mostafa, M. Relationship between schistosomiasis and bladder cancer.
Badawi, A. Nitrate, nitrite and N-nitroso compounds in human bladder cancer associated with schistosomiasis. Cancer 86 , — Grisham, M. Nitric oxide. Physiological chemistry of nitric oxide and its metabolites: implications in inflammation.
Fukuto, J. Chemistry of nitric oxide: biologically relevant aspects. Beckman, J. Apparent hydroxyl radical production by peroxynitrite: implications for endothelial cell injury from nitric oxide.
USA 87 , — Fang, F. Mechanisms of nitric oxide-related antimicrobial activity. Schapiro, J. Inhibition of bacterial DNA replication by zinc mobilization during nitrosative stress.
USA , — Long, R. Mycobacteriocidal action of exogenous nitric oxide. Brunelli, L. The comparative toxicity of nitric oxide and peroxynitrite to Escherichia coli. Pacelli, R. Nitric oxide potentiates hydrogen peroxide-induced killing of Escherichia coli. Russell, C. The effect of nitric oxide on the growth of Escherichia coli. Experientia 21 , Shiloh, M. Evaluation of bacterial survival and phagocyte function with a fluorescence-based microplate assay.
Yu, K. Toxicity of nitrogen oxides and related oxidants on mycobacteria: M. Lung Dis. Helicobacter pylori is killed by nitrite under acidic conditions. Gut 42 , — Xu, J. The bactericidal effect and chemical reactions of acidified nitrite under conditions simulating the stomach. Braun, C. Marker exchange of the structural genes for nitric oxide reductase blocks the denitrification pathway of Pseudomonas stutzeri at nitric oxide. Bryk, R. Peroxynitrite reductase activity of bacterial peroxiredoxins.
Wolfe, M. Hydroxylamine reductase activity of the hybrid cluster protein from Escherichia coli. Antimicrobial effect of acidified nitrite on gut pathogens: importance of dietary nitrate in host defence.
Wallace, J. Nitric oxide in mucosal defense: a little goes a long way. Lanas, A. Nitrovasodilators, low-dose aspirin, other nonsteroidal anti-inflammatory drugs, and the risk of upper gastrointestinal bleeding.
Fiorucci, S. Gastrointestinal safety of NO-aspirin NCX in healthy human volunteers: a proof of concept endoscopic study. Inhalation of nasally derived nitric oxide modulates pulmonary function in humans.
Acta Physiol. Miyoshi, M. Dietary nitrate inhibits stress-induced gastric mucosal injury in the rat. Larauche, M. Protective effect of dietary nitrate on experimental gastritis in rats. Effect of dietary nitric oxide on gastric mucosal mast cells in absence or presence of an experimental gastritis in rats.
Zetterquist, W. Salivary contribution to exhaled nitric oxide. Silva Mendez, L. Antimicrobial effect of acidified nitrite on cariogenic bacteria. Oral Microbiol.
Weller, R. Nitric oxide is generated on the skin surface by reduction of sweat nitrate. Antimicrobial effect of acidified nitrite on dermatophyte fungi, Candida and bacterial skin pathogens. Carlsson, S. Effects of pH, nitrite, and ascorbic acid on nonenzymatic nitric oxide generation and bacterial growth in urine.
Nitric Oxide 5 , — In vitro evaluation of a new treatment for urinary tract infections caused by nitrate-reducing bacteria. Zweier, J. Enzyme-independent formation of nitric oxide in biological tissues. Modin, A. Nitrite-derived nitric oxide: a possible mediator of 'acidic-metabolic' vasodilation.
Kinetics and mechanism of the oxidation of human deoxyhemoglobin by nitrites. Reutov, V. NO-synthase and nitrite-reductase components of nitric oxide cycle. Biochemistry Mosc.
Cosby, K. Nitrite reduction to nitric oxide by deoxyhemoglobin vasodilates the human circulation. Millar, T. Xanthine oxidoreductase catalyses the reduction of nitrates and nitrite to nitric oxide under hypoxic conditions.
FEBS Lett. Godber, B. Reduction of nitrite to nitric oxide catalyzed by xanthine oxidoreductase. Li, H. Characterization of the magnitude and kinetics of xanthine oxidase-catalyzed nitrite reduction. Evaluation of its role in nitric oxide generation in anoxic tissues.
Alikulov, Z. Nitrate and nitrite reductase activity of milk xanthine oxidase. Biokhimiia 45 , — Kozlov, A. Various intracellular compartments cooperate in the release of nitric oxide from glycerol trinitrate in liver.
Richardson, G. The ingestion of inorganic nitrate increases gastric S -nitrosothiol levels and inhibits platelet function in humans. Nitric Oxide 7 , 24—29 A randomized trial of acidified nitrite cream in the treatment of tinea pedis. Klebanoff, S. Nitrite production by stimulated human polymorphonuclear leukocytes supplemented with azide and catalase.
Motteram, P. Energy conservation during the formate-dependent reduction of nitrite by Escherichia coli.