Heterotrophic nitrifiction by Arthrobacter sp

Arthrobacter sp. isolated from sewage oxidized ammonium to hydroxylamine, a bound hydroxylamine compound, a hydroxamic acid, a substance presumed to be a primary nitro compound, nitrite, and nitrate. The concentration of free hydroxylamine-nitrogen reached 15 mug/ml. The identification of hydroxylamine was verified by mass spectrometric analysis of its benzophenone oxime derivative. The bound hydroxylamine was tentatively identified as 1-nitrosoethanol on the basis of its mass spectrum, chemical reactions, and infrared and ultraviolet spectra. Hydroxylamine formation by growing cells was relatively independent of pH, but the accumulation of nitrite was strongly favored in alkaline solutions. The formation of hydroxylamine but not nitrite was regulated by the carbon to nitrogen ratio of the medium. The hydroxamic acid was the dominant product of nitrification in iron-deficient media, but hydroxylamine, nitrite, and 1-nitrosoethanol formation was favored in iron-rich solutions. Heterotrophic nitrification by Arthrobacter sp. was not inhibited by several compounds at concentrations which totally inhibited autotrophic nitrification.

Influence of temperature on the iron metabolism of a fluorescent pseudomonad

The iron requirement for maximal cell yields of a fluorescent pseudomonad increases as the temperature of incubation is increased. On a succinate salts medium, maximal cell yields are attained at iron concentrations of 0.10 mug/ml of added iron at 20 C and at 3.0 mug/ml of added iron at 28 C. This bacterium does not grow in the basal medium at 31 C even in the presence of 0.01 to 10 mug/ml of added iron. The inability to grow at the higher temperature is due to the loss, by this organism, of its ability to biosynthesize hydroxamate iron transport compounds at temperatures of 28 C and above, since supplementation with such compounds produced by this organism at lower temperatures promoted growth at 31 C. The biosynthesis of these compounds at lower temperatures contributes to the efficient utilization of iron by the bacterium.

Mechanism of nitrification by Arthrobacter sp

Resting cells of Arthrobacter sp. excrete as much as 60 mug of hydroxylamine-nitrogen per ml when supplied with ammonium. An organic carbon source in abundant supply is necessary for the oxidation. Resting cells oxidize hydroxylamine to nitrite and 1-nitrosoethanol, the former accumulating only when an exogenous carbon source is available. Cell-free extracts contain an enzyme catalyzing the formation of hydroxylamine from acetohydroxamic acid, a hydroxylamine-nitrite oxido-reductase, and an enzyme producing nitrite and nitrate from various primary nitro compounds. Nitrite is not produced from hydroxylamine by the extracts, but 1-nitrosoethanol is formed from hydroxylamine in the presence of acetate. 1-Nitrosoethanol is also produced from acetohydroxamic acid by these preparations. Nitrite was formed from hydroxylamine, however, by extracellular enzymes excreted by the bacterium.

Pathway of oxidation of pyruvic oxime by a heterotrophic nitrifier of the genus Alcaligenes: evidence against hydrolysis to pyruvate and hydroxylamine

A heterotrophic nitrifier of the genus Alcaligenes, which grows vigorously on pyruvic oxime, was tested by several methods for possible differences or similarities in metabolic performance between pyruvic oxime and its hydrolysis products, pyruvate and hydroxylamine. Major differences were observed between pyruvic oxime and one or both of the other reductants with regard to growth yield, rates of reductant uptake, rates of oxygen uptake, sensitivity of their oxidations to inhibition by thiocyanate, and performance in reductant pulse experiments. Other oximes, some of which are structural analogs of pyruvic oxime and all of which are potential sources of hydroxylamine, were not metabolized by cells or cell-free extract. Collectively the results indicate a pathway of oxidation of pyruvic oxime to nitrite and CO2 that does not involve its initial hydrolysis, but probably involves the oxidation of N and/or C before C-N bond breakage.

The metabolism of chlorpromazine and promethazine to give new "pink spots". Proposals for the mechanisms involved

Mechanisms are proposed for the removal, during metabolism, of the aminoalkyl side chain from chlorpromazine and promethazine and for the subsequent formation of nitroxides, N-hydroperoxides, N-oxyhydroperoxides and hydroxylamines from the phenothiazine nuclei.

Identification of N, O-dimethylhydroxylamine as a microbial degradation product of the herbicide, linuron

N, O-dimethylhydroxylamine was identified as a degradation product of linuron formed in the presence of extracts of Bacillus sphaericus ATCC 12123 by characterization of its dinitrophenyl derivative.

Nitrification of aspartate by Aspergillus flavus

Heterotrophic conversion of l-aspartic acid to nitrification products by Aspergillus flavus was studied in a replacement incubation system. Numerous amino acids supported nitrification; aspartate and glutamate were about equivalent as the best sources of nitrate. Addition of sodium bicarbonate to the incubation system substantially enhanced nitrate formation for all nitrifiable amino acids except aspartic acid, but the basis for the bicarbonate effect is obscure. The yield of nitrate from l-aspartate was not approached by forms of aspartic acid resulting from substitution on the beta carbon, the amino nitrogen, or the gamma carboxyl group or by aspartate presented as the d-configuration. There was no relationship between nitrate formation and the occurrence of such possible intermediates as nitrite, bound hydroxylamine, ammonia, aspergillic acid, and beta-nitropropionic acid. Uniformly labeled (14)C-l-aspartate that was nitrified in replacement incubation led to no accumulation of label in possible nitrification products in the culture filtrate. Label was found in components of the mycelium after acid hydrolysis, with heaviest accumulation in what appeared to be glucosamine and an unidentified compound, possibly acetylglucosamine. Detectable label was redistributed into serine, glycine, and threonine.

Reductive metabolism of aromatic nitro compounds including carcinogens by rabbit liver preparations

Reductive metabolism of aromatic nitro compounds was examined with rabbit liver preparations. Under anaerobic conditions, carcinogenic 2-nitrofluorene, 4-nitrobiphenyl, and 1-nitro-naphthalene were reduced to the corresponding hydroxylamines and amines, whereas the carcinogenic 1-nitropyrene was reduced only to the corresponding amine by liver cytosol in the presence of 2-hydroxypyrimidine, an electron donor of aldehyde oxidase. These metabolites were identified unequivocally by comparing their mass spectra and thin-layer chromatographic behaviors with those of the authentic samples. Both liver microsomes and cytosol catalyzed the reduction of these aromatic nitro compounds in varying degrees. The microsomes required reduced pyridine nucleotides for occurrence of the nitroreductase activities. In this case, reduced nicotinamide adenine dinucleotide phosphate was more effective than reduced nicotinamide adenine dinucleotide as an electron donor. The cytosol by itself exhibited some nitroreductase activities, which were markedly enhanced by addition of an electron donor of aldehyde oxidase, i.e., N1-methylnicotinamide or 2-hydroxypyrimidine. The full activities of the cytosol with the electron donor were much higher than those of the microsomes with the reduced pyridine nucleotide. Purified liver aldehyde oxidase, like the cytosol, exhibited significant nitroreductase activities in the presence of its electron donor. These results indicated that cytosolic aldehyde oxidase functions as a major enzyme responsible for the reduction of aromatic nitro compounds including carcinogens in rabbit liver.