Evaluation of Nitrate Synthesis by Intestinal Microorganisms in Vivo

Witter, JP; Gatley, S.J.; Balish, Edward

doi:10.1126/science.7244641

Cited by 26 publications

(8 citation statements)

References 18 publications

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“…We have since rejected this hypothesis, primarily because we have shown that both germ-free rats and conventional rats generate nitrate (22). This finding has been corroborated by others (35). The toxicological significance of extensive nitrate metabolism and ofnitrate biosynthesis is unknown at this time, although the probable involvement ofnitrite in these processes makes them of some toxicological interest.…”

Section: Resultsmentioning

confidence: 60%

Nitrate biosynthesis in man.

Green¹,

Luzuriaga²,

Wagner³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

559

262

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Nitrate metabolism was investigated in longterm metabolic balance studies on healthy young men. Under conditions of constant low ingestion of nitrate (<180 pumol/day per subject), the amount of nitrate excreted in urine was an average of 4-fold greater than the amount ingested. Balance studies with '5N03-showed that the source of the excess nitrate in urine was the endogenous biosynthesis of nitrate, rather than the emptying of a body pool. Nitrate biosynthesis occurred when nitrate ingestion was high as well as low, and the amounts synthesized appeared to be independent of intake and comparable to the amounts ingested from normal diets. Analysis of the '5N03-data also revealed that half of ingested nitrate was recovered as urinary nitrate. Because nitrate in urine is the net result of (i) intake, (ii) endogenous synthesis, and (iii) metabolic losses, the magnitude of the losses is such that, despite ongoing synthesis, the amount of nitrate in the urine ofpeople consuming most diets will be less than the amount ingested.Nitrosamines are potent animal carcinogens (1). Small amounts ofthese compounds are formed in some foods and in the animal and human body from the reaction ofamines and nitrite. A common precursor to nitrite is nitrate; higher than average levels of nitrate in some environments have been linked to elevated incidences of human cancer (2, 3). The environment is not the only source of nitrate: metabolic balance studies performed early in this century (4) and preliminary studies from our laboratory (5) corn starch dessert, and protein-free cookies (7). Mean energy intake was 46 kcal (1 cal = 4.184 J) per kg of body weight, with an average of-total calories from protein of 7.0%, from carbohydrates of 53%, and from fat of 40%.Another group of eight young men (mean age, 22; mean weight, 72 kg) participated in a second study lasting 56 days. During wk 1 of the study, the subjects consumed their freechoice diet. For the next 4 wk, they consumed the basal formula to which milk protein had been added. In addition, twice daily they consumed an omelette made of dried egg, water, and salt. Carbonated and sucrose beverages, a cornstarch dessert, and protein-free cookies provided the remainder of calories in the diet.For the final 3 wk of the study, 25 g of standardized wheat bran preparation (American Association ofCereal Chemists certified food grade wheat bran) was added to the basal formula. The diet otherwise was identical to that of the previous 4 wk. Daily protein intake was higher in this second study-1.5 g of protein per kg of body weight. Mean daily calories consisted of 14% from protein, 45% from carbohydrate, and 41% from fat.A third study involved another six young men (mean age, 24; mean weight, 79 kg) and lasted for 1 wk. The subjects consumed the high protein soy, milk, and egg diet utilized in the second study, with no addition of bran. On the penultimate morning of this study, after an overnight 10-hr fast, each subject was given a 300-mg (3500 jmol) dose of Na'5NO3 (.99% N = 15N) in ...

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Section: Resultsmentioning

confidence: 60%

Nitrate biosynthesis in man.

Green¹,

Luzuriaga²,

Wagner³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

559

262

View full text Add to dashboard Cite

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“…However, in the human intestine, low oxygen tension permits E. coli to grow by fermentation or respiration using an alternative electron acceptor. As nitrate is readily available in the human intestine (14 μmol/kg [36]) and can be readily utilized by intestinal bacterial flora including E. coli [37,38] we examined succinate selection using this alternate electron receptor. Interestingly, host nitrate synthesis can be stimulated in response to infections caused by gastroenteric pathogens [38].…”

Section: Resultsmentioning

confidence: 99%

Polymorphism and selection of rpoS in pathogenic Escherichia coli

et al. 2009

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BackgroundThough RpoS is important for survival of pathogenic Escherichia coli in natural environments, polymorphism in the rpoS gene is common. However, the causes of this polymorphism and consequential physiological effects on gene expression in pathogenic strains are not fully understood.ResultsIn this study, we found that growth on non-preferred carbon sources can efficiently select for loss of RpoS in seven of ten representative verocytotoxin-producing E. coli (VTEC) strains. Mutants (Suc++) forming large colonies on succinate were isolated at a frequency of 10-8 mutants per cell plated. Strain O157:H7 EDL933 yielded mainly mutants (about 90%) that were impaired in catalase expression, suggesting the loss of RpoS function. As expected, inactivating mutations in rpoS sequence were identified in these mutants. Expression of two pathogenicity-related phenotypes, cell adherence and RDAR (red dry and rough) morphotype, were also attenuated, indicating positive control by RpoS. For the other Suc++ mutants (10%) that were catalase positive, no mutation in rpoS was detected.ConclusionThe selection for loss of RpoS on poor carbon sources is also operant in most pathogenic strains, and thus is likely responsible for the occurrence of rpoS polymorphisms among E. coli isolates.

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“…This observation is based on excess excretion of nitrate in urine by human subjects or animals ingesting a low-nitrate diet. The origin of this nitrate was subsequently shown to occur in mammalian tissues as assessed by nitrate balance studies in germ-free and conventional rats (13)(14)(15). It is well known that the oxidation of ammonia to nitrate is a continuous process of the nitrogen cycle (16,17).…”

mentioning

confidence: 99%

Mammalian nitrate biosynthesis: incorporation of 15NH3 into nitrate is enhanced by endotoxin treatment.

Wagner¹,

Young²,

Tannenbaum³

1983

Proc. Natl. Acad. Sci. U.S.A.

177

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determined by conversion of NO-to nitrobenzene, which was then analyzed by gas chromatography/mass spectrometry (22) on a HP5992 (Hewlett Packard, Palo Alto, CA). The gas chromatographic separation was carried out on a Durabond DB-5 fused silica capillary column (Quadrex, New Haven, CT) with a helium carrier flow rate of 1 ml/min, initial column temperature of 1100C, and temperature programming of 40C/min.

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Evaluation of Nitrate Synthesis by Intestinal Microorganisms in Vivo

Cited by 26 publications

References 18 publications

Nitrate biosynthesis in man.

Nitrate biosynthesis in man.

Polymorphism and selection of rpoS in pathogenic Escherichia coli

Mammalian nitrate biosynthesis: incorporation of 15NH3 into nitrate is enhanced by endotoxin treatment.

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