Nitrate reduction

Nitrate Inhibition of Nodulation in Legumes

Published in Peter M. Gresshoff, Molecular Biology of Symbiotic Nitrogen Fixation, 2018

Bernard J. Carroll, Anne Mathews

The lack of an unequivocal explanation for nitrate inhibition of nitrogenase activity by carbohydrate deprivation or the products of nitrate reduction in legume species indicated that some other control mechanism may be operative. In view of the variable O2 diffusion barrier probably operative in legume nodule,146,148,151 a plausible explanation for inhibition was that O2 supply to the bacteroids was limited in the presence of nitrate. Evidence in support of this hypothesis has been obtained for soybean107,152 and white clover.147,153 Nitrate inhibition of nitrogenase (acetylene reduction) activity was alleviated when soybean root systems were assayed at 60% O2.152 While this was not observed in nitrate-inhibited white clover plants,147 the diffusion resistance to O2 increased considerably as estimated by respiratory CO2 production.153 This discrepancy may reflect a difference between soybean and white clover in the rate of adjustment to the oxygen diffusion barrier, and the latter may be able to respond more quickly.

Published in Ronald M. Atlas, James W. Snyder, Handbook Of Media for Clinical Microbiology, 2006

Ronald M. Atlas, James W. Snyder

Use: For the differentiation of Mycobacterium species based on nitrate reduction. After growth of cells in appropriate medium, nitrate reduction is determined by making a suspension of cells in TB nitrate reduction broth and adding hydrochloric acid, sulfa-nilamide, and N-naphylenendiamine. Nitrate reduction turns the medium pink. Mycobacterium tuberculosis reduces nitrate and turns the medium deep pink within 1 min. Mycobacterium bovis does not reduce nitrate and does not change the medium.

Biology of microbes

Published in Philip A. Geis, Cosmetic Microbiology, 2006

Daniel K. Brannan

Other more common mechanisms for assimilating nitrogen are ammonia incorporation and assimilatory nitrate reduction. Ammonia is easily incorporated into amino acids by forming the alanine amino acid directly by amination of pyruvate using the alanine dehydrogenase enzyme. Alternatively, a cell can form glutamate (an amino acid) by aminating α-ketoglutarate (a TCA cycle intermediate) using the glutamate dehydrogenase enzyme. Once these two amino acids have been formed, the ammonia they carry (now called an α-amino group) can be transferred to other carbon skeletons of other catabolic intermediates by transamination to form several other amino acids.

Spatial fractionation of phosphorus accumulating biofilm: stratification of polyphosphate accumulation and dissimilatory nitrogen metabolism

Published in Biofouling, 2022

Didrik Villard, Torgeir Saltnes, Gjermund Sørensen, Inga Leena Angell, Sondre Eikås, Wenche Johansen, Knut Rudi

The spatial fractionation of phosphorus accumulating biofilm revealed an unexpected stratification of genes and bacteria involved in polyphosphate accumulation and dissimilatory nitrogen metabolism. Polyphosphate accumulation and nitrification was found to be associated with the inner biofilm layer, suggesting a colocalization of these processes in the deep layer of the biofilm. Genes for nitrate reduction were more abundantly associated with the inner biofilm layer, while genes for nitric- and nitrous oxide reductions were more abundant in the outer biofilm layer. The spatial distribution of these genes suggest that different electron acceptors were utilized in the different layers of the biofilm by the denitrification bacteria. The current study shows the importance and potential of biofilm fractionation in combination with metagenomic analyses for enhancing knowledge on biofilm structure and functionality.

Citizen-science based study of the oral microbiome in Cystic fibrosis and matched controls reveals major differences in diversity and abundance of bacterial and fungal species

Published in Journal of Oral Microbiology, 2021

Jesse R. Willis, Ester Saus, Susana Iraola-Guzmán, Elena Cabello-Yeves, Ewa Ksiezopolska, Luca Cozzuto, Luis A. Bejarano, Nuria Andreu-Somavilla, Miriam Alloza-Trabado, Andrea Blanco, Anna Puig-Sola, Elisabetta Broglio, Carlo Carolis, Julia Ponomarenko, Jochen Hecht, Toni Gabaldón

Alloprevotella presents an interesting case that may merit further study on its own regarding CF. Species in this genus reduce nitrate in the saliva which contributes to the anti-inflammatory response to periodontitis [122–124], so its lower abundance in CF here could be linked in part to lower incidence of periodontitis. However, the nitrate reduction in CF patients seems to be a more complicated process. When it is metabolized to nitric oxide (NO), it has an anti-inflammatory effect in the airways of CF individuals. Some studies have shown that precursors to NO, like nitrate and nitrite, are higher in the saliva and exhaled breath condensate (EBC) of CF patients than in those of controls, but nonetheless, the amount of exhaled NO was lower in CF [125,126]. One proposed explanation is that NO may be produced normally in CF, but its diffusion is inhibited in the thick mucus produced in CF airways [127], though these first two studies suggest that there is an impairment in the formation of NO in CF patients. Another study found that increasing the intake of dietary nitrate led to an increase in exhaled NO as compared to placebo treatments [128]. From this information, we cannot extrapolate to determine the exact mechanism in the impairment of the NO cycle in CF, but the low abundance of the nitrate-reducing genus Alloprevotella forms a link to this process that may warrant a deeper investigation.

The role of iron-oxidizing bacteria in biocorrosion: a review

Published in Biofouling, 2018

David Emerson

An additional source of confusion regarding microbial Fe-oxidation centers around nitrate-dependent Fe-oxidation. Nitrate-reduction, typically coupled to the oxidation of organic matter, is a very common microbial metabolism. The kinetics and thermodynamics of this reaction coupled to the oxidation of Fe(II) are favorable for a microbially mediated process that could support growth, and there is little doubt that numerous nitrate-reducing bacteria can catalyze Fe(II)-oxidation (Weber et al. 2006). The problem lies in showing that these microbes are growing via this process, i.e. using energy gained from nitrate-dependent Fe-oxidation to fix CO2, rather than using organic matter as their carbon and energy source. The confounding factor is that the first step in nitrate reduction (Table 1) is the production of nitrite (NO2) that can rapidly oxidize Fe(II) chemically (Carlson et al. 2013). As yet, there are no reports of pure cultures of bacteria that can be readily sustained growing solely on Fe(II) and nitrate as either obligate, or facultative nitrate-dependent Fe-oxidizers. There is a well-documented consortium of microbes, the ‘Straub culture’, that has been maintained for years and grows via nitrate-dependent Fe-oxidation, although its potential to be involved in MIC is unknown (He et al. 2016). The distinction between anaerobic iron-oxidation being linked to a product of heterotrophic nitrate reduction, vs being a lithotrophic process, is important in terms of determining if a nitrate-dependent biocorrosion community can sustain itself via lithoautotrophy, rather than requiring a significant input of organic matter.