Nitrite

About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.

A survey of heterotrophic micro-organisms from soil for ability to form nitrite and nitrate.

Abstract: SUMMARY: A total of 978 cultures of heterotrophic organisms were isolated from twelve actively nitrifying soils; each isolate was tested for ability to form nitrite or nitrate in glucose peptone broth. None of the isolates yielded substantial amounts of nitrite; concentrations found did not exceed 2 μg. nitrite-N/ml. Almost 7% of the isolates formed nitrite-N in excess of 0·2 μg./ml., while slightly over 2% yielded more than 0·5 μg./ml. Fungus isolates were the most numerous and most active nitrite producers; fifteen of the fungi formed nitrate in addition to nitrite. Concentrations of 5–45 μg. nitrate-N/ml. were recorded for the active fungi. Further isolations of fungi from ten soils of diverse properties resulted in 353 cultures but only three of these formed nitrate. One of these cultures yielded 90 μg. nitrate-N/ml. after 14 days growth in the test medium. Most of the fungi which produced nitrate (16 of the 18 active cultures) were identified as Aspergillus flavus. A Penicillium sp., and a Cephalosporium sp. also formed low concentrations of nitrate. Each isolate of A. flavus obtained from soil proved capable of nitrate formation. Strains of A. flavus were encountered which did not yield nitrate, but these had been obtained from culture collections, and had been carried on artificial media for many years. Some stock cultures of A. flavus, several cultures of A. flavus and one of A. glaucus, freshly isolated from wheat seed, also were active nitrate producers. Ammonium sulphate and urea media supported growth of soil fungus isolates but not nitrate formation. Other organic nitrogen substrates in order of increasing effectiveness in nitrate production were: yeast extract, peptone, Protone and casein.

L-arginine-dependent production of a reactive nitrogen intermediate by macrophages of a uricotelic species.

Abstract: L-arginine-dependent production of reactive nitrogen intermediates (RNIs: nitric oxide, nitrite, and nitrate) by mammalian macrophages has been proposed to occur via an L-arginine oxidative deimination pathway and is known to be responsible for certain antineoplastic and antimicrobial effector functions. The present study represents the first examination of this pathway in a non-mammalian vertebrate. Because chickens, unlike mammals, lack a urea cycle and are incapable of de novo synthesis of L-arginine, the possible existence of an avian macrophage pathway for production of RNIs is questionable. We have defined conditions under which chicken macrophages are able to produce nitrite. Sephadex-elicited chicken peritoneal macrophages required a bacterial lipopolysaccharide (LPS from Escherichia coli) signal to produce nitrite during 24 hour cultures in the presence of L-arginine. As little as 5 ng/ml LPS resulted in significant nitrite production in culture. The relationship of nitrite production to both LPS and L-arginine levels was dose-dependent. D-arginine was unable to substitute for L-arginine but also produced no inhibitory effect. In contrast, L-NG-monomethyl arginine showed a significant inhibitory effect on nitrite production. A virus-transformed chicken macrophage cell line, HD11, also produced nitrite in a dose-dependent manner relative to both LPS and L-arginine concentration. Concentrations as low as 5 ng/ml LPS and 0.1 mM L-arginine resulted in significant nitrite production, while maximum levels of nitrite production were obtained using greater than or equal to 0.5 micrograms/ml LPS and greater than or equal to 0.4 mM L-arginine. These results indicate that chicken macrophages can produce RNIs. This production is dependent upon activation and is influenced by local L-arginine concentration. Moreover, because the chicken does not possess the ability to synthesize arginine and has an absolute nutritional requirement for this amino acid, the chicken represents a highly controllable system to examine the in vivo effects of L-arginine on macrophage-related immune functions.