Nitrate availability

The submitter used reagent-grade silver nitrate available from Merck Company, Inc. 

Nitrate Available to plants, converted to N2 gas under anaerobic conditions Mobile... 

In the absence of 02 the E. coli FNR protein induces proteins of the anaerobic respiration pathways. Nitrate also has its own two-component system that senses nitrate availability and activates transcription of enzymes catalyzing nitrate respiration.162 An expanded two-component system induces sporulation in Bacillus subtilis in response to poor growth conditions.163164 The crystal structure of one of two response regulators (SpoOF) has a structure closely related to that of CheY and the nitrate response regulator NarL. 

Allen AE, Booth MG, Verity PG, Frischer ME (2005) Influence of nitrate availability on the distribution and abundance of heterotrophic bacterial nitrate assimilation genes in the Barents Sea during summer. Aquat Microb Ecol 39 247-255... 

Nijburg J. W., Coolen M. J. L., Gerards S., Klein Gunnewiek P. J. A., and Laanbroek H. J. (1997) Effects of nitrate availability and the presence of Glyceria maxima on the composition and activity of the dissimilatory nitrate-reducing bacteria community. Appl. Environ. Microbiol. 63, 931-937. 

Suboxic metabolism, which includes nitrate, manganese and iron reduction, does not generally seem to form a discrete layer due to the relatively low levels of nitrate available under natural conditions and the insoluble nature of manganese oxyhydroxides and iron oxides. These reactions appear to be restricted, where they are apparent at all, to micro-environments, but since, of the reduction reactions in Table 6.1, they are the only ones to generate alkaline conditions, they may be important for the precipitation and preservation of carbonate minerals. 

The phosphate accumulation process is described in current models as follows (Henze et al., 1999). Some heterotrophic bacteria, so-called phosphate-accumulating organisms, grow under aerobic (dissolved oxygen available) as well as anoxic (no dissolved oxygen, but nitrate available) conditions on intracellular organic material... 

Dissimilatory reduction of nitrate to ammonia is performed by obligate and facultative anaerobes with fermentative metabolism, including Clostridium and Bacillus species (Tiedje, 1988). These organisms, in contrast to denitrifiers, usually do not rely on nitrate as electron acceptor. Therefore, DNRA involves 8e transfer as compared to 5e transfer for denitrification, suggesting that more organic substrate can be potentially degraded by DNRA. However, nitrate availability under DNRA conditions is usually very low because much of the nitrate formed during nitrification under aerobic conditions is rapidly consumed by denitrifiers in adjacent anaerobic environments. 

In interior wetland areas, the source of nitrate is primarily nitrification, and denitrification rates in these areas are limited by nitrate availability. Several studies have shown that denitrification rates increase with an increase in nitrate concentration. Half-saturation constants (one of the Michaelis-Menton kinetics parameter) reported for denitrification range from 27 to 344 pM for lake and marine sediments (Seitzinger, 1988) and 130 to 1,200 pM for soils (Firestone, 1982). Low half-saturation constants probably reflect carbon limitation in soil or diffusion of nitrate from aerobic sites to anaerobic sites. 

The interaction between phosphodiesterase type-5 inhibitors and nitrates is established, clinically important, potentially serious and even possibly fatal. Sildenafil and organic nitrates of any form are contraindicated both for erectile dysfunction (within 24 hours of each other ) and for pulmonary hypertension because of the risk of precipitating serious hypotension, or even myocardial infarction. The ACC/AHA Expert consensus document provides a useful list of many of the organic nitrates available, whieh inelude glyeeryl trinitrate (nitroglycerin), isosorbide mononitrate, isosorbide dinitrate and illicit substances such as amyl nitrite. ... 

---