scholarly journals Chemostat studies on the regulation of glucose metabolism in Pseudomonas aeruginosa by citrate

1973 ◽  
Vol 132 (2) ◽  
pp. 129-140 ◽  
Author(s):  
F. M.-W. Ng ◽  
E. A. Dawes
Keyword(s):  
Growth Rate ◽  
Pseudomonas Aeruginosa ◽  
Glucose Metabolism ◽  
Glucose Concentration ◽  
Isocitrate Dehydrogenase ◽  
Glucose Medium ◽  
Metabolic Products ◽  
Induction Of Enzymes ◽  
Specific Activities ◽  
Glucose 6 Phosphate Dehydrogenase

The effect of the relative concentrations of citrate and glucose on the regulation of key enzymes of the direct oxidative, phosphorylative, Entner–Doudoroff and pentose-cycle pathways of glucose metabolism in Pseudomonas aeruginosa has been investigated in continuous culture under conditions of NH4+-limitation. For comparison isocitrate dehydrogenase and aconitase were also assayed. Measurements were made for steady-state and transient conditions and the effect of growth rate was also studied. When cells grew on 75mm-citrate the glucose concentration had to attain 6–8mm before significant induction of enzymes of glucose metabolism occurred; the specific activities increased further as the result of both raising the glucose concentration to 30mm and then subsequently lowering the citrate to 60mm and then to 45mm. The specific activities of the glucose enzymes increased immediately during the transient period between the steady states characteristic of growth on 6mm- and 8mm-glucose, the increase continuing for about two doubling times. The converse experiment of adding increasing citrate concentrations to 45mm-glucose medium revealed an immediate induction of the citrate-transport system, oxidation of citrate following the increase in citrate concentration up to 8mm. Between 8mm- and 16mm-citrate a marked repression of gluconate, glucose 6-phosphate and 6-phosphogluconate dehydrogenases and the Entner–Doudoroff enzymes occurred. Increased growth rate in citrate medium resulted in decreased specific activities of glucose 6-phosphate dehydrogenase and isocitrate dehydrogenase. Increased growth rate in citrate–glucose medium gave decreased specific activities of isocitrate dehydrogenase and aconitase whereas the activities of some of the glucose enzymes decreased initially but then increased at the highest growth rate (0.5h-1), at which a marked increase in glucose utilization occurred. These observations accord with the regulation of glucose enzymes by induction with glucose or its metabolites and repression by citrate or its metabolic products.

scholarly journals Adaptation of the small intestine during pregnancy and lactation in the rat

1979 ◽  
Vol 184 (2) ◽  
pp. 245-251 ◽  
Author(s):  
K Burdett ◽  
C Reek
Keyword(s):  
Small Intestine ◽  
Lactate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Enzyme Activities ◽  
Unit Area ◽  
Mucosal Epithelium ◽  
Pregnancy And Lactation ◽  
Enzyme Change ◽  
Specific Activities ◽  
Glucose 6 Phosphate Dehydrogenase

During pregnancy and lactation in the rat the small intestine in general and the mucosal epithelium in particular gain weight. The specific activities of sucrase, lactate dehydrogenase and succinate-tetrazolium reductase remain constant and those of glucose 6-phosphate dehydrogenase and isocitrate dehydrogenase increase. There is no evidence that the reported decrease in absorption per unit area or weight of mucosal epithelium during pregnancy and lactation is due to decreases in enzyme activities within the epithelium. The pattern of enzyme change shows that the response of the gut to the stimuli of pregnancy and lactation must be a complex one, possibly involving increases in the specific activities of some enzymes.

scholarly journals Regulation and Adaptation of Glucose Metabolism of the Parasitic Protist Leishmania donovani at the Enzyme and mRNA Levels

1999 ◽  
Vol 181 (16) ◽  
pp. 4863-4872 ◽  
Author(s):  
Benno H. ter Kuile
Keyword(s):  
Growth Rate ◽  
Energy Metabolism ◽  
Glucose Metabolism ◽  
Leishmania Donovani ◽  
Glucose Consumption ◽  
Cellular Protein ◽  
Insect Vector ◽  
Mrna Levels ◽  
Specific Activities ◽  
Excess Glucose

ABSTRACT Adaptation of the glucose metabolism of Leishmania donovani promastigotes (insect stage) was investigated by simultaneously measuring metabolic rates, enzyme activities, message levels, and cellular parameters under various conditions. Chemostats were used to adapt cells to different growth rates with growth rate-limiting or excess glucose concentrations. L. donovanicatabolized glucose to CO2, succinate, acetate, and pyruvate in ratios that depended on growth rate and glucose availability. Rates of glucose consumption were a linear function of growth rate and were twice as high in excess glucose-grown cells as in glucose-limited organisms. The major end product was CO2, but organic end products were also formed in ratios that varied strongly with growth conditions. The specific activities of the 14 metabolic enzymes measured varied by factors of 3 to 17. Two groups of enzymes adapted specific activities in parallel, but there was no correlation between the groups. The activities of only one group correlated with specific rates of glucose metabolism. Total RNA content per cellular protein varied by a factor of 6 and showed a linear relationship with the rate of glucose consumption. There was no correlation between steady-state message levels and activities of the corresponding enzymes, suggesting regulation at the posttranscriptional level. A comparison of the adaptation of energy metabolism in L. donovani and other species suggests that the energy metabolism ofL. donovani is inefficient but is well suited to the environmental challenges that it encounters during residence in the sandfly, its insect vector.

ACUTE ENZYME HISTOCHEMICAL CHANGES IN THE ZONA GLOMERULOSA OF THE RAT ADRENAL CORTEX

1968 ◽  
Vol 59 (3) ◽  
pp. 508-518
Author(s):  
J. D. Elema ◽  
M. J. Hardonk ◽  
Joh, Koudstaal ◽  
A. Arends
Keyword(s):  
Peritoneal Dialysis ◽  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Adrenal Cortex ◽  
Isocitrate Dehydrogenase ◽  
Hydroxysteroid Dehydrogenase ◽  
Zona Glomerulosa ◽  
Acute Changes ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Histochemical Changes

ABSTRACT Acute changes in glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase activity in the zona glomerulosa of the rat adrenal cortex were induced by peritoneal dialysis with 5 % glucose. Although less clear, the activity of 3β-ol-hydroxysteroid dehydrogenase also seemed to increase as well. No changes were seen in the activity of succinate dehydrogenase. Dialysis with 0.9 % NaCl had no effect on any of the enzymes investigated. The possible significance of these observations is discussed.

CONTINUOUS CULTURE OF BRUCELLA ABORTUS S.19

1961 ◽  
Vol 7 (4) ◽  
pp. 491-505 ◽  
Author(s):  
Andreas H. W. Hauschild ◽  
Hilliard Pivnick
Keyword(s):  
Growth Rate ◽  
Continuous Culture ◽  
Dilution Rate ◽  
Brucella Abortus ◽  
Specific Growth ◽  
Limiting Factor ◽  
Continuous Growth ◽  
Viable Cells ◽  
Metabolic Products ◽  
Growth Of Bacteria

An apparatus is described for the continuous growth of bacteria. Brucella abortus S.19 has been grown in continuous culture for periods up to 3 weeks with populations up to 2 × 1011viable cells per ml and without the establishment of nonsmooth variants.Concentrations between 3 × 109and 2 × 1011cells per ml could be maintained as a function of the dilution rate without the requirement of a known limiting factor in the medium. In a series of steady-state conditions, the specific growth rate increased steadily up to 0.28 hour−1with decreasing population levels.Incidence of mutants was governed by the dilution rate and could also be reduced by various chelating substances.In continuous growth combined with continuous dialysis, population levels were approximately twice those obtained in continuous growth without dialysis. The effect of dialysis appears to be the continuous removal of growth-limiting metabolic products.

scholarly journals Simultaneous Catabolite Repression between Glucose and Toluene Metabolism in Pseudomonas putida Is Channeled through Different Signaling Pathways

2007 ◽  
Vol 189 (18) ◽  
pp. 6602-6610 ◽  
Author(s):  
Teresa del Castillo ◽  
Juan L. Ramos
Keyword(s):  
Glucose Metabolism ◽  
Pseudomonas Putida ◽  
Catabolite Repression ◽  
Carbon Sources ◽  
Flux Analysis ◽  
Glucose Determination ◽  
Net Flux ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Metabolism Gene

ABSTRACT Pseudomonas putida KT2440(pWW0) can use toluene via the TOL plasmid-encoded catabolic pathways and can use glucose via a series of three peripheral chromosome-encoded routes that convert glucose into 6-phosphogluconate (6PG), namely, the glucokinase pathway, in which glucose is transformed to 6PG through the action of glucokinase and glucose-6-phosphate dehydrogenase. Alternatively, glucose can be oxidized to gluconate, which can be phosphorylated by gluconokinase to 6PG or oxidized to 2-ketogluconate, which, in turn, is converted into 6PG. Our results show that KT2440 metabolizes glucose and toluene simultaneously, as revealed by net flux analysis of [13C]glucose. Determination of glucokinase and gluconokinase activities in glucose metabolism, gene expression assays using a fusion of the promoter of the Pu TOL upper pathway to ′lacZ, and global transcriptomic assays revealed simultaneous catabolite repression in the use of these two carbon sources. The effect of toluene on glucose metabolism was directed to the glucokinase branch and did not affect gluconate metabolism. Catabolite repression of the glucokinase pathway and the TOL pathway was triggered by two different catabolite repression systems. Expression from Pu was repressed mainly via PtsN in response to high levels of 2-dehydro-3-deoxygluconate-6-phosphate, whereas repression of the glucokinase pathway was channeled through Crc.

Catalase released from beneficial and plant-pathogenic pseudomonads by water and chloroform treatments

1994 ◽  
Vol 40 (8) ◽  
pp. 630-636
Author(s):  
J. I. Pounder ◽  
A. J. Anderson
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Dismutase ◽  
Water Treatment ◽  
Pseudomonas Syringae ◽  
Small Proportion ◽  
Plant Colonization ◽  
Periplasmic Proteins ◽  
Specific Activities ◽  
Leaf Pathogen ◽  
Glucose 6 Phosphate Dehydrogenase

Survival of pseudomonads during plant colonization may involve bacterial catalases to degrade the hydrogen peroxide produced by the plant. The specific activities of catalases in lysates from two saprophytic isolates of Pseudomonas putida and Pseudomonas fluorescens and three races of Pseudomonas syringae pv. glycinea were similar. To explore the location of the bacterial catalases, cells of the pathogenic and saprophytic pseudomonads were treated with chloroform, which is reported to release periplasmic proteins. Although catalase was released by chloroform treatment, the cytoplasmic enzymes isocitrate dehydrogenase, superoxide dismutase, and glucose-6-phosphate dehydrogenase were also detected. These proteins may have come from lysis of a small proportion of the cells rather than the periplasm. Water treatment of cells also released amounts of protein similar to those derived from chloroform treatment. Similar responses were found from both pathogenic and saprophytic strains. The release of catalase and proteins from the leaf pathogen P. syringae pv. glycinea race 0 and the root-associated saprophyte P. putida decreased as the cultures aged. With P. putida and P. syringae pv. glycinea race 0, the single isozyme of catalase released by water and chloroform treatment also was detected in lysates. Additional catalase isozymes were present in lysates as the cultures aged.Key words: periplasmic proteins, survival.

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