Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Microbial nitrogen utilization”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2026

Genome-resolved multi-omics provide new insights into microbial nitrogen utilization by the rumen microbiota.

BACKGROUND: Optimizing nitrogen (N) utilization in ruminant production systems holds both economic and environmental significance. However, traditional paradigms of N metabolism, derived primarily from well-studied model rumen bacteria, do not fully reflect the diverse and complex N metabolism in the rumen ecosystem. RESULTS: To address this gap, we utilized comparative genomics and genome-resolved multi-omics analyses using a curated set of microbial genomes to investigate N assimilation and regulation in rumen microbes. We discovered that well-established mechanisms of ammonia assimilation and regulation, such as the glutamine synthetase (GS)/glutamate synthase (GOGAT) pathways and their regulatory proteins, are absent in many of the predominant rumen microbes, which likely utilize alternative pathways for ammonia assimilation. These findings challenge the applicability of E. coli-based N regulation models to rumen bacteria in response to ammonia availability. We further linked polysaccharide utilization and ammonia assimilation across hundreds of rumen microbial species. Furthermore, we identified specific microbial species involved in ureolysis and denitrification, as well as phages carrying auxiliary metabolic genes involved in N assimilation. Using an animal trial involving 11 pairs of lamb twins in a crossover design, we demonstrated that dietary crude protein (CP) at 10% and 13% had minimal impact on rumen microbiome composition and expression of N assimilation genes. Instead, changes in concentrate levels altered N assimilation, notably increasing expression of amino acid biosynthesis pathways. CONCLUSION: These findings indicate a nuanced, species-specific microbial response to dietary interventions, highlighting the limitations of traditional N metabolism models applied to rumen microbes and the need for more granular studies of rumen microbial ecosystems.

Multiomics↗
PubMed1986

Microbial numbers, rumen fermentation, and nitrogen utilization of steers fed wet or dried brewers' grains.

Holstein steers were fed corn silage supplemented with either wet or dried brewers' grains to determine effects of heat drying commercial brewers' grains. Four rumen-fistulated steers were fed a 12.5% crude protein diet in a single reversal design experiment. Brewers' grains supplied 45% of the protein of the diet. Bacterial numbers, concentration of ciliated protozoa, and ammonia concentration in the rumen were higher, and rumen pH was lower, for steers fed wet brewers' grains. Concentrations of rumen volatile fatty acids were similar for both diets. Ruminal digestibility of dry matter decreased when wet versus dried brewers' grains were fed (56.9 versus 39.3%). The rate of dry matter passage from the rumen was faster with wet brewers' grains. In Experiment 2, 12 steers were in a 2 X 2 factorial design. Diets contained wet or dried brewers' grains supplemented at 22 or 40% of the diet dry matter (12.5 and 14.5% crude protein). Nitrogen retention was increased in steers fed the higher crude protein diet. Apparent digestible nitrogen, acid detergent fiber nitrogen, and nitrogen retention were higher with wet versus dried brewers' grains. Plasma essential and nonessential amino acids were also higher in steers fed wet brewers' grains. Alteration in microbial numbers, fermentation measurements, and nitrogen utilization were associated with more soluble nitrogen with wet (13.4%) versus dried (3.3%) brewers' grains.

Amino Acids↗
PubMed1985

The effect of provision of the first-limiting amino acid, gastrointestinal microbial activity and the level of nitrogen intake on protein utilization and energy digestibility in rats.

1. The present work with growing rats was undertaken to study the effect of protein quality, gastrointestinal microbial activity and the level of nitrogen intake on protein utilization and energy digestibility. The experiment involved a total of thirty-six dietary treatments in a 9 x 4 factorial design, with five rats per treatment. The thirty-six diets resulted from nine protein sources. Each diet was composed of a basal N-free mixture plus minerals and vitamins, with N sources added at the expense of the N-free mixture to provide 15.0 gN/kg dry matter (DM) in the first three protein-addition treatments and 30.0 gN/kg DM in the fourth protein-addition treatment. The nine protein sources were soya-bean meal, casein, wheat gluten, skim-milk powder, meat-and-bone meal, wheat bran, barley, wheat and cooked brown beans (Phaseolus vulgaris). The four formulations for each protein source incorporated the protein unsupplemented at 15.0 gN/kg DM, unsupplemented at 30.0 gN/kg DM, or supplemented at 15.0 gN/kg DM with the estimated first-limiting amino acid or the antibiotic Nebacitin. 2. With all protein sources, the inclusion of the first-limiting amino acid had no effect on either protein or energy digestibility. 3. The microbial activity in the digestive tract affected protein utilization and energy digestibility to a different degree depending primarily on the level and type of dietary fibre. True protein digestibility (TD) of skim-milk powder and brown beans, both rich in easily-fermentable energy, increased from 0.959 to 1.000 and from 0.680 to 0.777 respectively by the addition of Nebacitin. TD of the other protein sources was only marginally affected by the antibiotic treatment. Only with brown beans was the biological value (BV) markedly affected by Nebacitin with an increase from 0.482 to 0.557 by the treatment. Energy digestibility was significantly lower in rats given antibiotic with soya-bean meal, wheat bran, barley, wheat and brown beans. 4. The effect of level of N intake on protein utilization was dependent on both protein quality and the fibre concentration of the diet. Protein sources with high BV were more affected than proteins of lower BV. It was concluded that TD is not always independent of dietary protein concentration.

Amino Acids↗
PubMed1986

[Nitrogen metabolism in the large intestine of ruminants. 3. Microbial utilization of intracecally administered 14C- and 15N-marked urea in the large intestine of sheep in simultaneous intracecal administration of partially hydrolyzed straw meal].

Two experiments were performed on sheep, receiving on maintenance level a pelleted straw ration high in crude fibre (straw, 70.5%; dried sugar beet pulp, 12%; cereals, 10%; urea, 2%; ammonium hydrogen carbonate, 3%; minerals 2,5%). The animals were fitted with ileo-caecal re-entrant cannulas. The effects of the introduction of HC1-partly hydrolysed straw meal into the digesta of the large intestine on the digestion processes in that segment were studied. Under these conditions the metabolism of 14C and 15N labelled urea, which was given into the caecum, was estimated. In experiment 1 (E 1; 2 animals) unlabelled, precollected digesta were hourly reintroduced together with 14C and 15N labelled urea via the caecal cannula. In experiment 2 (E 2; 3 animals) the digesta were supplemented with partly hydrolysed straw meal (10% of the mean daily DM-intake with the ration). The supplement of partly hydrolysed straw meal caused an increase of the 15N excretion with faeces from 13.4% (E 1) to 19.8% (E 2) of the dose. The 15N was mainly incorporated in the bacterial fraction (98% E 1; 96% E 2). As a reason for the increased 15N incorporation into the bacterial fraction of 106.4 mg15N' in E 2 vs. 67.3 mg15N' in the experiment without straw meal supplement the higher supply of energy as fermentable carbohydrates was assumed.

Animals↗
PubMed1989

Microbial ureases: significance, regulation, and molecular characterization.

Microbial ureases hydrolyze urea to ammonia and carbon dioxide. Urease activity of an infectious microorganism can contribute to the development of urinary stones, pyelonephritis, gastric ulceration, and other diseases. In contrast to these harmful effects, urease activity of ruminal and gastrointestinal microorganisms can benefit both the microbe and host by recycling (thereby conserving) urea nitrogen. Microbial ureases also play an important role in utilization of environmental nitrogenous compounds and urea-based fertilizers. Urease is a high-molecular-weight, multimeric, nickel-containing enzyme. Its cytoplasmic location requires that urea enter the cell for utilization, and in some species energy-dependent urea uptake systems have been detected. Eucaryotic microorganisms possess a homopolymeric urease, analogous to the well-studied plant enzyme composed of six identical subunits. Gram-positive bacteria may also possess homopolymeric ureases, but the evidence for this is not conclusive. In contrast, ureases from gram-negative bacteria studied thus far clearly possess three distinct subunits with Mrs of 65,000 to 73,000 (alpha), 10,000 to 12,000 (beta), and 8,000 to 10,000 (gamma). Tightly bound nickel is present in all ureases and appears to participate in catalysis. Urease genes have been cloned from several species, and nickel-containing recombinant ureases have been characterized. Three structural genes are transcribed on a single messenger ribonucleic acid and translated in the order gamma, beta, and then alpha. In addition to these genes, several other peptides are encoded in the urease operon of some species. The roles for these other genes are not firmly established, but may involve regulation, urea transport, nickel transport, or nickel processing.

Animals↗
PubMed1975

Nitrogen requirement and utilization in dairy cattle.

Formulation of dairy cow rations should consider the following points regarding nitrogen utilization by lactating cows. (a) Maintenance of ruminal ammonia nitrogen in excess of 5 mg/100 ml rumen fluid has no effect on microbial protein production. (b)Supplemental nonprotein nitrogen is not utilized in typical dairy and feedlot beef rations containing more than 12 to 13% crude protein(dry matter basis). (c)Nonprotein nitrogen is approximately equal to true protein as a source of nitrogen in typical dairy and feedlot rations containing not more than 12 to 13% crude protein. (d)A scheme based upon metabolizable protein (absorbable protein) for calculating requirements and comparing protein sources is superior to crude or digestible protein designations. Ultimate expression of the requirement may be in terms of crude protein for the sake of simplicity. (e)One kilogram of crude protein, regardless of nitrogen source, equals about .75kg metabolizable protein in typical dairy and feedlot beef rations containing not more than 12 to 13% crude protein. One kilogram of plant protein (true protein) fed in excess of an amount equivalent to 12 to 13% dietary protein equals about .3 kg metabolizable protein. (f)Protein supplementation of lactating cows might be related more to stage of lactation than to milk production. (g)Lactating cows having above average lactational ability may benefit from dietary protein as high as 16 to 17% (dry matter basis) during the first third of lactation. (h)Cows in the latter two-thirds of lactation appear to require 12.5% dietary protein or less. (i)Plant protein (true protein) should be the supplemental sources of nitrogen during the first third of lactation, with NPN providing most, if not all, the supplemental nitrogen during the last two-thirds of lactation.

Ammonia↗
PubMedDate not supplied

Incorporation of N from intravenously administered 15N labelled urea into the bacterial protein in the sheep.

The experiment carried out on two wethers demonstrated that nitrogen of intravenously injected urea, labelled with 15N was incorporated into total and bacterial nitrogen fraction of the digesta flowing through the rumen and duodenum. The amount of 15N in the bacterial fraction flowing throught the rumen and duodenum was relatively low in comparison with the amount of 15N in the total nitrogen (14,8% and 8,1% in the rumen and 6,6% and 7,9% in the duodenum. The ratio of the amount of bacterial-N to total-N in the rumen content (12,7 and 7,5%) was only slightly lower than the ratio of bacterial 15N to total 15N. In the duodenum this ratio was a little higher (8,7 and 10,0%). Blood urea nitrogen was utilized only partly in biosynthesis of bacterial protein. The results showed that only a small amount of blood urea nitrogen retained in the organism was utilized for microbial protein synthesis and the majority in some different way.

Animals↗
PubMed1976

Utilization of dried microbial cells grown on methanol in a semi-purified diet for growing pigs.

1. Twenty-four pigs (mean body-weight 44 kg) were used to determine the digestibilities of energy, nitrogen and amino acids in dried microbial cells (DMC) grown on methanol and in white fish meal (WFM). N utilization and the excretion of various nitrogenous compounds were also studied. 2. Semi-purified diets containing DMC, WFM or no protein source were offered at the rate of 1 kg fresh food/d. Daily N intakes were 26-5, 24-7 and 0-65 g respectively. 3. Mean metabolic faecal N determined with the protein-free diet was 1-11 g/d (1-26 g/kg dry matter (DM) eaten) for the two experiments. The corresponding endogenous urinary N value was 2-91 g/d. 4. Daily urinary N output of pigs given the diet with WFM was significantly greater than that of pigs given the diet with DMC, with the result that N retention, net protein utilization and biological value were higher for pigs given DMC. 5. Apparent and true digestibility of amino acids were higher for the diet with DMC than for the diet with WFM. 6. N excretion in the form of ammonia, urea, uric acid and allantoin accounted for 81, 91 and 99% of the total N excreted by the groups given the protein-free diet, DMC and WFM respectively. Pigs given DMC excreted greater quantities of allantoin-N and less urea-N than pigs given WFM.

Amino Acids↗
PubMed1979

Appearance of 15N-labeled intestinal microbial amino acids in the venous blood of the pig colon.

Two experiments were done to determine whether pigs possess the ability to absorb amino acids synthesized from urea nitrogen by indigenous microbes in the large intestine. Incorporation of [15N]urea into amino acid fractions of bacterial cells from the rectum and of the deproteinized incubated medium were examined in an experiment in vitro. The isotope was incorporated into 17 amino acids and the ammonia fraction of these samples. The absorption of the microbial amino acids from the colon was investigated by determination of the 15N concentration of the free amino acids in the venous blood of the colon after infusion of the 15N-labeled microorganisms into the cecum. The increase of 15N concentration was also observed in the plasma-free amino acids (threonine, isoleucine, phenylalanine, lysine, histidine, arginine, aspartic acid, serine, alanine, cystine) of the blood from the colic branch of the ileocolic vein. The results of these experiments indicated that pigs have the ability to utilize the microbial amino acids synthesized from urea nitrogen in the large intestine.

Amino Acids↗
PubMed1978

Production of animal protein from nonprotein nitrogen chemicals.

Ruminants obtain amino acids (AA) from microbial protein synthesized in the rumen and from feed proteins that escape ruminal degradation. Synthesis of microbial protein provides a mechanism for obtaining AA from NPN. Effectiveness of NPN utilization depends upon production and utilization of ammonia by rumen microbes. Because ammonia is produced from protein and NPN, feeding proteins resistant to microbial degradation forces utilization of ammonia derived from NPN. The quantity of microbial cells formed in the anaerobic rumen fermentation system is primarily dependnt upon energy supply but can be modulated by types and supplies of other nutrients (i.e. amino-N, minerals growth factors) and by growth rate of rumen bacteria. Potential quantities of NPN that can be utilized with different feed ingredients can be estimated from amounts of feed protein degraded in the rumen, and requiring transformation into protein via growth of rumen microbes, and from amounts of energy provided by feed ingredients. High energy feed ingredients with low amounts of degradable protein are most favorable for NPN utilization, but NPN has also been used successfully with high-fibrous, low energy feed materials. Growth, lactation and reproduction have been obtained on diets containing more than 97% of the nitrogen from NPN, but microbial protein alone cannot provide quantities of AA needed for high levels of productivity. Regulating ruminal degradation of dietary protein and utilizing NPN for rumen protein production is a highly desirable strategy for producing human foods with ruminants.

Amino Acids↗
PubMed1979

Microbial transaminase activities and their relationship with bovine rumen metabolites.

Two each adult male crossbred cattle and murrah buffalo were fed a diet of alfalfa hay, chopped wheat straw, and concentrate mixture. Total rumen transaminase activity of cattle was higher than that of buffalo. Rumen protozoal fractions showed higher total transaminase activity than bacterial fractions in both ruminant species. Besides generally studied glutamate oxalacetate transaminase and glutamate pyruvate transaminase, a large number of other microbial transaminases also have been detected in the rumen of both the ruminant species. Bacterial fractions of rumen liquor were devoid of transaminases utilizing tryptophan, threonine, and lysine as their substrates. Ruminal ammonia and nonprotein nitrogen were correlated positively with microbial transaminases in both species. Transamination reactions may be important for assimilation of ruminal ammonia to cellular proteins.

Alanine Transaminase↗
PubMed1975

Utilization of nitrogen from soybean meal, casein, zein, and urea by mature sheep.

The utilization of nitrogen contained in soybean meal, casein, zein, and urea was studied in 12 mature wethers. Net microbial synthesis rates during the 6-hour period after feeding corresponded to ruminal ammonia concentrations, suggesting that the ruminal ammonia level in these experiments was a limiting factor in microbiol protein synthesis. Maximum conversion of dietary nitrogen to microbial nitrogen in the rumen during a 24-hour period was estimated to be 62.5, 85.3, 40.9, and 90.1%, respectively, for soybean meal, casein, zein, and urea. Estimated production rates of acetic, propionic, butyric, isovaleric, and valeric acids during the first 6 hours after feeding suggested that zein supported the lowest microbial activity in the rumen, and that urea supplementation resulted in isovaleric and valeric acids production rates equivalent to or greater than rates when the other nitrogen supplements were present in the diet. Daily endogenous urinary and metabolic fecal nitrogen determined by regression analysis utilizing soybean meal as the only nitrogen supplement were 72 mg/kg body weight0.75 and 340 mg/100 g of dry matter intake. Biological values of 84.8, 78.3, 84.3, and 76.4 were obtained for soybean meal, casein, zein, and urea, respectively.

Animal Feed↗
PubMed1985

Nitrogen metabolism by the microbial flora of the rabbit caecum.

The dense microbial flora of the rabbit caecum consisted chiefly of bacteria (10(11)/g) with small numbers of yeast cells (10(6)/g). Using strictly anaerobic technique, 23% of the direct microscopic cell count was cultivated and 55% of the cultivatable bacteria utilized ammonia as the sole source of nitrogen. Ureolytic bacteria were isolated from the caecal lumen and mucosa and were identified as Bacteroides vulgatus, Clostridium clostridiiforme, Bacillus spp. and Staphylococcus spp. Ammonia assimilation by the bacterial flora of the caecum was by incorporation into alpha-oxoglutarate catalysed by NADPH-linked glutamate dehydrogenase.

Ammonia↗
PubMed1977

Microbial metabolism of aromatic nitriles. Enzymology of C-N cleavage by Nocardia sp. (Rhodochrous group) N.C.I.B. 11216.

1. An organism utilizing benzonitrile as sole carbon and nitrogen source was isolated by the enrichment-culture technique and identified as a Nocardia sp. of the rhodochrous group. 2. Respiration studies indicate that nitrile degradation proceeds through benzoic acid and catechol. 3. Cell-free extracts of benzonitrile-grown cells contain an enzyme that catalyses the conversion of benzonitrile directly into benzoic acid without intermediate formation of benzamide. 4. This nitrilase enzyme was purified by DEAE-cellulose chromatography and gel filtration on Sephadex G-100 in the presence and absence of substrate. The purity of the enzyme was confirmed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing on polyacrylamide gel. 5. The enzyme shows a time-dependent substrate-activation process in which the substrate catalyses the association of inactive subunits of mol.wt. 45000 to form the polymeric 12-unit active enzyme of mol.wt. 560000. The time required for complete association is highly dependent on the concentration of the enzyme, temperature and pH. 6. The associated enzyme has a pH optimum of 8.0 and K(m) with benzonitrile as substrate of 4mm. The activation energy of the reaction as deduced from the Arrhenius plot is 51.8kJ/mol. 7. Enzyme activity is inhibited by thiol-specific reagents and several metal ions. 8. Studies with different substrates indicate that the nitrilase is specific for nitrile groups directly attached to the benzene ring. Various substituents in the ring are compatible with activity, though ortho-substitution, except by fluorine, renders the nitrile invulnerable to attack. 9. The environmental implications of these findings and the possible significance of the enzyme in the regulation of metabolism are discussed.

Aminohydrolases↗
PubMed1985

Microbial mineralization of ring-substituted anilines through an ortho-cleavage pathway.

Moraxella sp. strain G is able to utilize as sole source of carbon and nitrogen aniline, 4-fluoroaniline, 2-chloroaniline, 3-chloroaniline, 4-chloroaniline (PCA), and 4-bromoaniline but not 4-iodoaniline, 4-methylaniline, 4-methoxyaniline, or 3,4-dichloroaniline. The generation time on PCA was 6 h. The pathway for the degradation of PCA was investigated by analysis of catabolic intermediates and enzyme activities. Mutants of strain G were isolated to enhance the accumulation of specific pathway intermediates. PCA was converted by an aniline oxygenase to 4-chlorocatechol, which in turn was degraded via a modified ortho-cleavage pathway. Synthesis of the aniline oxygenase was inducible by various anilines. This enzyme exhibited a broad substrate specificity. Its specific activity towards substituted anilines seemed to be correlated more with the size than with the electron-withdrawing effect of the substituent and was very low towards anilines having substituents larger than iodine or a methyl group. The initial enzyme of the modified ortho-cleavage pathway, catechol 1,2-dioxygenase, had similar characteristics to those of corresponding enzymes of pathways for the degradation of chlorobenzoic acid and chlorophenol, that is, a broad substrate specificity and high activity towards chlorinated and methylated catechols.

Aniline Compounds↗
PubMed1975

Relationship between ruminal ammonia and nonprotein nitrogen utilization by ruminants. II. Application of published evidence to the development of theoretical model for predicting nonprotein nitrogen utilization.

Results from published experiments dealing with several aspects of nitrogen utilization by ruminants were used to test the concept of zero utilization of nonprotein nitrogen under conditions where more ammonia (greater than 5 mg ammonia nitrogen/100 ml) is in the rumen than can be converted to microbial protein. Results from experiments where the flow of non-ammonia nitrogen to the abomasum of sheep was measured indicate that when urea was the source of supplemental nitrogen, a constant quantity of amino acids reached the abomasum for all rations ranging from 10 to 23% crude protein. From growth studies, addition of nonprotein nitrogen to low protein, high energy rations caused an improved rate of gain. Additions of nonprotein nitrogen to rations resulting in predicted ruminal ammonia concentrations greater than 5 mg ammonia nitrogen/100 ml rumen fluid were without benefit. From lactation studies, nonprotein nitrogen supplementation did not improve milk production if the ration contained more than 12.5% crude protein prior to supplementation or if the predicted ruminal ammonia concentration was greater than 4 mg ammonia nitrogen/100 ml rumen fluid. The importance of the amino acid requirement of the animal as well as the composition of the ration in designing and evaluating nitrogen supplementation studies is discussed.

Ammonia↗
PubMed1976

Dynamics of fermentation of a purified diet and microbial growth in the rumen.

Ruminal fermentation and disappearance of glucose, starch, and cellulose, and incorporation of glucose and starch into microbial cells were estimated in a fistulated Jersey cow fed twice daily a purified diet containing urea as the sole nitrogen source. Estimated rumen volume was 59.8 liters. Turnover time and rate of passage of rumen contents were 33.4 h and 1.8 liters per h. Turnover times of glucose, starch, and cellulose were .17, 4.7, and 14.2 h. Fermentation times of glucose, starch, and cellulose were .17, 5.5, and 25.1 h. Percentages of glucose, starch, and cellulose utilized in the rumen were 99.4, 85.4, and 60.6. Thus, 18.5% of the carbohydrate fed bypassed rumen fermentation, and 81.5% was utilized in the rumen. All glucose disappeared from the rumen within an hour. An average of 32.1, 43.0, and 14%, respectively, of glucose utilized was incorporated into microbial cells, volatile fatty acids, and carbon dioxide. Percentage of starch incorporated into cells varied, with time being highest 2 h after feeding at 40% and lowest at 20%, 10 h after feeding. Respective percentages of starch incorporated into microbial cells, volatile fatty acids, and carbon dioxide were 32.4, 45.9; and 13.3. Total microbial protein and cell yields per kilogram carbohydrate utilized in the rumen were 77.1 and 117.5 g. Microbial cell yield per mole (estimated) of adenosine triphosphate was 16.2 g.

Adenosine Triphosphate↗