• Journal of Microbiology and Biotechnology
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• v.16 no.7
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• pp.999-1009
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• 2006

Physiological, biochemical and genetic studies of Corynebacterium glutamicum, a workhorse of white biotechnology used for amino acid production, led to a waste knowledge mainly about amino acid biosynthetic pathways and the central carbon metabolism of this bacterium. Spurred by the availability of the genome sequence and of genome-based experimental methods such as DNA microarray analysis, research on genetic regulation came into focus. Recent progress on mechanisms of genetic regulation of the carbon, nitrogen, sulfur and phosphorus metabolism in C. glutamicum will be discussed.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1200-1210
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• 2004

Metabolic flux analysis was established by adapting previous stoichiometric model developed during growth with cellulose to cell grown with cellobiose for further direct comparison of the bacterial metabolism. In carbon limitation with cellobiose, a shift from acetate-ethanol fermentation to ethanol-lactate fermentation is observed and the pyruvate overflow is much higher than with cellulose. In nitrogen limitation with cellobiose, the cellodextrin and exopolysaccharide overflows are much higher than on cellulose. In carbon and nitrogen saturation with cellobiose, the cellodextrin, exopolysaccharide, and free amino acids overflows reach the highest levels observed but all remain limited on cellulose. By completely shunting the cellulosome, the use of cellobiose allows to reach much higher carbon consumption rates which, in return, highlights the metabolic limitation of C. cellulolyticum. Therefore, the physical nature of the carbon source has a profound impact on the metabolism of C. cellulolyticum and most probably of other cellulolytic bacteria. For cellulolytic bacteria, the use of soluble carbon substrate must carefully be taken into consideration for the interpretation of results. Direct comparison of metabolic flux analysis from cellobiose and cellulose revealed the importance of cellulosome, phosphoglucomutase and pyruvate-ferredoxin oxidoreductase in the distribution of carbon flow in the central metabolism. In the light of these findings, future directions for improvement of cellulose catabolism by this bacterium are discussed.

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.326-336
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• 2016

Saccharomyces cerevisiae is one of the most employed cell factories for the production of bioproducts. Although monomeric hexose sugars constitute the preferential carbon source, this yeast can grow on a wide variety of nitrogen sources that are catabolized through central nitrogen metabolism (CNM). To evaluate the effects of internal perturbations on nitrogen utilization, we characterized strains deleted or overexpressed in GLT1, encoding for one of the key enzymes of the CNM node, the glutamate synthase. These strains, together with the parental strain as control, have been cultivated in minimal medium formulated with ammonium sulfate, glutamate, or glutamine as nitrogen source. Growth kinetics, together with the determination of protein content, viability, and reactive oxygen species (ROS) accumulation at the single cell level, revealed that GLT1 modulations do not significantly influence the cellular physiology, whereas the nitrogen source does. As important exceptions, GLT1 deletion negatively affected the scavenging activity of glutamate against ROS accumulation, when cells were treated with H₂O₂, whereas Glt1p overproduction led to lower viability in glutamine medium. Overall, this confirms the robustness of the CNM node against internal perturbations, but, at the same time, highlights its plasticity in respect to the environment. Considering that side-stream protein-rich waste materials are emerging as substrates to be used in an integrated biorefinery, these results underline the importance of preliminarily evaluating the best nitrogen source not only for media formulation, but also for the overall economics of the process.

• Journal of Microbiology and Biotechnology
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• v.19 no.1
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• pp.23-36
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• 2009

In the present work, the metabolic network of primary metabolism of the slow-growing myxobacterium Sorangium cellulosum was reconstructed from the annotated genome sequence of the type strain So ce56. During growth on glucose as the carbon source and asparagine as the nitrogen source, So ce56 showed a very low growth rate of $0.23\;d^{-1}$, equivalent to a doubling time of 3 days. Based on a complete stoichiometric and isotopomer model of the central metabolism, $^{13}C$ metabolic flux analysis was carried out for growth with glucose as carbon and asparagine as nitrogen sources. Normalized to the uptake flux for glucose (100%), cells recruited glycolysis (51%) and the pentose phosphate pathway (48%) as major catabolic pathways. The Entner-Doudoroff pathway and glyoxylate shunt were not active. A high flux through the TCA cycle (118%) enabled a strong formation of ATP, but cells revealed a rather low yield for biomass. Inspection of fluxes linked to energy metabolism revealed that S. cellulosum utilized only 10% of the ATP formed for growth, whereas 90% is required for maintenance. This explains the apparent discrepancy between the relatively low biomass yield and the high flux through the energy-delivering TCA cycle. The total flux of NADPH supply (216%) was higher than the demand for anabolism (156%), indicating additional reactions for balancing of NADPH. The cells further exhibited a highly active metabolic cycle, interconverting $C_3$ and $C_4$ metabolites of glycolysis and the TCA cycle. The present work provides the first insight into fluxes of the primary metabolism of myxobacteria, especially for future investigation on the supply of cofactors, building blocks, and energy in myxobacteria, producing natural compounds of biotechnological interest.

• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.114-122
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• 2023

A family of signal transduction pathways known as wingless type (Wnt) signaling pathways is essential to developmental processes like cell division and proliferation. Mutation in Wnt signaling results in a variety of diseases, including cancers of the breast, colon, and skin, metabolic disease, and neurodegenerative disease; thus, the Wnt signaling pathways have been attractive targets for disease treatment. However, the complicatedness and large involveness of the pathway often hampers pinpointing the specific targets of the metabolic process. In our current study, we investigated the differential metabolic regulation by the overexpression of the Wnt signaling pathway in a timely-resolved manner by applying high-throughput and un-targeted metabolite profiling. We have detected and annotated 321 metabolite peaks from a total of 36 human embryonic kidney (HEK) 293 cells using GC-TOF MS and LC-Orbitrap MS. The un-targeted metabolomic analysis identified the radical reprogramming of a range of central carbon/nitrogen metabolism pathways, including glycolysis, TCA cycle, and glutaminolysis, and fatty acid pathways. The investigation, combined with targeted mRNA profiles, elucidated an explicit understanding of activated fatty acid metabolism (β-oxidation and biosynthesis). The findings proposed detailed mechanistic biochemical dynamics in response to Wnt-driven metabolic changes, which may help design precise therapeutic targets for Wnt-related diseases.

• Korean Journal of Pharmacognosy
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• v.36 no.1 s.140
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• pp.56-59
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• 2005

Urease plays an important role in the urea metabolism and the effect of urease activity on human and environment is enormous. For instance, urease acts as a virulence factor of the urinary and gastrointestinal tracts infections in human and animal, being involved in kidney stone formation, catheter encrusatation, pyelonephritis, ammonia encephalopathy, hepatic coma, and urinary tract infections. Widespread urease activity in soil induces a plant damage due to ammonia toxicity and pH increase. Therefore, urease activity regulation through urease inhibitors would lead to an enhanced efficiency of urea nitrogen uptake in plants and to the improved therapeutic strategies for ureolytic bacterial infections. To search for new inhibitory compounds on urease activity from herbs, MeOH extracts of herbs were screened. Among of them, the MeOH extracts of Areca catechu exhibited an excellent inhibitory effect on urease activity. Two compounds were isolated from the ethyl acetate fraction by the activity guided fractionation. Their chemical structures were identified as (+)-catechin(compound I) and allantoin(compound II) by spectroscopic evidence, respectively. Compound I showed a stronger inhibitory effect on urease activity than compound II.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.6
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• pp.827-835
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• 2009

Insulin has crucial roles in energy metabolism in all mammals but has been less studied in ruminants. An experiment was conducted to investigate the effects of hypoinsulinemia induction on appetite, performance, carcass composition and blood metabolite levels in sheep. Treatments were intravenous injection of four doses of streptozotocin; 0, 25, 50 and 75 mg/kg BW named C, L, M and H, respectively. Twenty male lambs were divided into four treatment groups. Animals in group H could not continue the experiment because of abnormalities. The duration of the experiment was eight consecutive weeks, and injection was performed at the end of week 3. Feed and water intakes were measured weekly and weight changes of animals were recorded and used for calculation of other growth parameters. Blood samples were collected weekly via venipuncture at fasting and 2.5 h post-prandial and analyzed for hormones and blood metabolites. Results showed a marked hypoinsulinemia in group M with significant decrease in fasted and postprandial insulin concentrations and also fasted leptin concentrations vs. the control group C (p<0.05). Group M showed significant increases in blood glucose, triglycerides, cholesterol, total protein, blood urea nitrogen and ketone body levels vs. group C (p<0.05). After injection, animals in group M showed diabetic hyperphagia and enhanced water intake as compared to group C (p<0.05) but, despite increased feed intake, they did not gain more weight than controls (p<0.05), and consequently, their feed conversion ratio was greater. Protein and fat contents of meat and liver were not significantly different among groups (p>0.05). In conclusion, the results suggested a regulatory role of insulin in energy metabolism of ruminants by exerting two opposing effects; central catabolic and peripheral anabolic.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.5
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• pp.655-659
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• 2003

Forty eight lambs (24 each of Malpura and Mutton synthetic breeds) were weaned at 90 days of age and divided into two groups. One group of 12 lambs from each of the two breeds was maintained on low energy (52% TDN) and the other group of 12 on high energy (58% TDN) feedlot ration until 6 of the lambs attained 20 kg and the other 6 attained 25 kg live weight in each of the two groups. Daily feed intake and weekly body weights were recorded. Conventional metabolism trials were conducted on the two breeds and the two rations. The growth rate was found to be higher for lambs on high energy ration (p<0.01). The growth rate was also higher for higher target weight groups (p<0.01). The breed did not significantly affect the live weight gains. Mutton synthetic lambs required less number of days to reach 20 kg live weights but took more time to reach 25 kg target weight as compared to Malpura lambs (p<0.01). The lambs of both the breeds reached 25 kg live weight earlier on high energy than those on low energy ration (p<0.01). The dry matter intake, irrespective of breed, was significantly higher (4.57% or 93.4 g per kgW$^{0.75}$) on low energy than that on high energy ration (4.20% or 87.2 g per kg W$^{0.75}$). The digestibility coefficients of all the nutrients excepting crude fibre were significantly higher on high energy diet irrespective of the breed. Lambs on low energy ration, however, digested the crude fibre more than those on the high energy ration (p<0.05). Although there were no significant differences in the intakes of nitrogen, calcium and phosphorus, the balance of nitrogen was higher on high energy ration. The DCP and TDN values were 9.70 and 52.76% for low energy and 9.89 and 57.68 % for high energy ration, respectively. The dressing percentages on live weight basis were 50.2 on low and 51.6 on high energy ration, 50.5 at 20kg and 51.3 at 25 kg slaughter weight and 51.0 in Malpura and 50.8 in Mutton synthetic lambs, respectively. The percent of bones in the carcass was higher on low energy ration in Mutton synthetic lambs at 20 kg slaughter weight than others. It was concluded that the performance of the lambs in respect of mutton production was significantly better on high energy ration fed upto 25 kg slaughter weight with no or little breed differences.

• Korean Journal of Veterinary Service
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• v.41 no.4
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• pp.239-244
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• 2018

Mycobacterium tuberculosis (M. tuberculosis) complex is the causative agent of tuberculosis (TB) in humans and bovine TB in mammalian hosts and grows very slowly. Selenium is a central molecule in nitrogen metabolism and an essential ingredient for all living cells and glutamic acid. The effects of selenium on the growth of M. tuberculosis, a representative slow-growing Mycobacterium species, were investigated and measured using the BacT Alert 3D System (MB/BacT System). Sodium selenate, at a final concentration of $10{\mu}g/mL$, reduced the average time-to detection (TTD) to 197.2 hours (95% confidence interval (CI), 179.6~214.8) from 225.1 hours (95% CI, 218~232.0) in the control culture media (P<0.05). The TTD did not increase with $\text\tiny{L}$-glutamate concentrations up to $10{\mu}g/mL$, but a significant reduction in the TTD was observed in the presence of $20{\mu}g/mL$ ${\text\tiny{L}}$-glutamate in culture media (P<0.05). In conclusion, selenate and ${\text\tiny{L}}$-glutamate enhance the growth of M. tuberculosis.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.3
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• pp.297-307
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• 1995

Anatomical and physiological studies of sink tissues are required for better understanding the biological plant growth system and energy metabolism Anatomy of root growth zones of two genotypes of tall fescue (Festuca arundinacea Schreb.) receiving 50 or 200 ppm N were determined, Cross-sectional anatomy and cells responses of root growth zones were observed and examined. Rapid radial root expansion occurred within the first 1.0 mm from root apex, and then increased gradually for both genotypes and N levels. Another increase in diameter occurred at high N after cell elongation slowed near 3.0 mm. Area of the central cylinder cell increased rapidly near the root apex. However, it then decreased again about 1.0 to 1.5 mm from the apex, perhaps because of pressure from the rapid increase of root diameter due largely to an increasing proportion of cortex and epidermis or hypodermis in the distal portion of the root growth zone. Root area from the apical initial to 6.0 mm distal consisted of 10 to 18% epidermis or exodermis, 67 to 79% cortex, and 10 to 22% vascular cylinder cells containing cambium cells (6 to 20%) and xylem cells (0.8 to 2.5%). These data indicate that N application affects root growth radially by increasing mainly cortex cell area, with less effect on epidermis and central cylinder cells.