scholarly journals Microaerophilic Cooperation of Reductive and Oxidative Pathways Allows Maximal Photosynthetic Membrane Biosynthesis in Rhodospirillum rubrum

2003 ◽  
Vol 69 (11) ◽  
pp. 6577-6586 ◽  
Author(s):  
Hartmut Grammel ◽  
Ernst-Dieter Gilles ◽  
Robin Ghosh
Keyword(s):  
Rhodospirillum Rubrum ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Pyridine Nucleotide ◽  
Tricarboxylic Acid ◽  
Physiological Adaptation ◽  
Marker Enzyme ◽  
Photosynthetic Membrane ◽  
Acid Cycle ◽  
Microaerophilic Conditions

ABSTRACT The purple nonsulfur bacterium Rhodospirillum rubrum has been employed to study physiological adaptation to limiting oxygen tensions (microaerophilic conditions). R. rubrum produces maximal levels of photosynthetic membranes when grown with both succinate and fructose as carbon sources under microaerophilic conditions in comparison to the level (only about 20% of the maximum) seen in the absence of fructose. Employing a unique partial O2 pressure (pO2) control strategy to reliably adjust the oxygen tension to values below 0.5%, we have used bioreactor cultures to investigate the metabolic rationale for this effect. A metabolic profile of the central carbon metabolism of these cultures was obtained by determination of key enzyme activities under microaerophilic as well as aerobic and anaerobic phototrophic conditions. Under aerobic conditions succinate and fructose were consumed simultaneously, whereas oxygen-limiting conditions provoked the preferential breakdown of fructose. Fructose was utilized via the Embden-Meyerhof-Parnas pathway. High levels of pyrophosphate-dependent phosphofructokinase activity were found to be specific for oxygen-limited cultures. No glucose-6-phosphate dehydrogenase activity was detected under any conditions. We demonstrate that NADPH is supplied mainly by the pyridine-nucleotide transhydrogenase under oxygen-limiting conditions. The tricarboxylic acid cycle enzymes are present at significant levels during microaerophilic growth, albeit at lower levels than those seen under fully aerobic growth conditions. Levels of the reductive tricarboxylic acid cycle marker enzyme fumarate reductase were also high under microaerophilic conditions. We propose a model by which the primary “switching” of oxidative and reductive metabolism is performed at the level of the tricarboxylic acid cycle and suggest how this might affect redox signaling and gene expression in R. rubrum.

scholarly journals Control of the production of exo-β-N-acetylglucosaminidase by Bacillus subtilis B. Derepression during gluconeogenesis and initial stages of sporulation

1973 ◽  
Vol 134 (1) ◽  
pp. 271-281 ◽  
Author(s):  
Stephen J. Brewer ◽  
Roger C. W. Berkeley
Keyword(s):  
Bacillus Subtilis ◽  
Exponential Growth ◽  
Phosphoenolpyruvate Carboxylase ◽  
Metal Ion ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Defined Medium ◽  
Tricarboxylic Acid ◽  
Carboxylase Activity ◽  
Acid Cycle

1. The control of exo-β-N-acetylglucosaminidase (EC 3.2.1.30) production by Bacillus subtilis B growing on a chemically defined medium was studied. 2. The enzyme was repressed during exponential growth by those carbon sources that enter the glycolytic pathway above the level of phosphoenolpyruvate. When exponential growth ceased as a result of low concentrations of the nitrogen, carbon or metal ion components of the medium, the enzyme was formed and its amount could be increased by the addition of cell-wall fragments as inducer. 3. The enzyme was de-repressed and could be induced during exponential growth on non-glycolytic compounds metabolized directly into pyruvate, acetyl-CoA or tricarboxylic acid cycle intermediates. 4. The major difference in the metabolism of the organism utilizing these two groups of compound was the existence of high activities of phosphoenolpyruvate carboxylase required for gluconeogenesis. 5. It is concluded that the de-repression of glucosaminidase occurs when the only principal change detected in the intermediary metabolism of the organism was the presence of high activities of phosphoenolpyruvate carboxylase. 6. When the organism was grown on media containing repressing compounds, the enzyme was only de-repressed on entry of the cells into the initial stages of sporulation, where phosphoenolpyruvate carboxylase activity, even in the presence of excess of glucose, increased in parallel with glucosaminidase, neutral proteinase and alkaline phosphatase activities. 7. These results suggest a strong link, at the level of the tricarboxylic acid cycle, between the control of phosphoenolpyruvate carboxylase and the control of the de-repression of glucosaminidase and sporulation.

Utilization of fructose and glutamate by Rhodospirillum rubrum

1968 ◽  
Vol 14 (5) ◽  
pp. 493-498 ◽  
Author(s):  
Margaret S. Gibson ◽  
Chih H. Wang
Keyword(s):  
Carbon Source ◽  
Sole Carbon Source ◽  
Rhodospirillum Rubrum ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Glycolytic Pathway ◽  
Light Conditions ◽  
Acid Cycle

Fructose served as sole carbon source for the growth of Rhodospirillum rubrum anaerobically under light or aerobically in the dark while glucose did not. Glucose was not utilized by the organism at all. Radiorespirometric studies, using 14C specifically labelled fructose as substrate, revealed that fructose is catabolized exclusively via the Embden–Meyerhof–Parnas (EMP) glycolytic pathway. Both L-glutamic and D-glutamic acids can be utilized by this organism, via the tricarboxylic acid cycle (TCA) pathway, under either aerobic-dark or anaerobic-light conditions.

ON THE MECHANISM OF GLUCOSE-6-PHOSPHATE OXIDATION IN CELL-FREE EXTRACTS OF XANTHOMONAS PHASEOLI (XP8)

1958 ◽  
Vol 36 (1) ◽  
pp. 669-689 ◽  
Author(s):  
R. M. Hochster ◽  
H. Katznelson
Keyword(s):  
Triosephosphate Isomerase ◽  
Tricarboxylic Acid Cycle ◽  
Pyridine Nucleotide ◽  
Tricarboxylic Acid ◽  
Minor Role ◽  
Pathogenic Organism ◽  
Acid Cycle ◽  
High Concentrations ◽  
Hydrolysis Of ◽  
Splitting System

Extracts of the plant pathogenic organism Xanthomonas phaseoli contain both TPN- and DPN-linked glucose-6-phosphate dehydrogenases as well as a DPN-specific glyceraldehyde phosphate dehydrogenase. DPNH oxidase is very active and sensitive to high concentrations of cyanide. No evidence could be found for the presence of pyridine nucleotide transhydrogenase.Ribose-5-phosphate is metabolized via the pentose cycle; sedoheptulose phosphate is an intermediate and other criteria of the functioning of the pentose cycle are met when ribose-5-phosphate is the substrate. The same system also functions with 6-phosphogluconate as substrate but at a level which suggests that this pathway is not of great significance.The Entner–Doudoroff 6-phosphogluconate-splitting pathway is the major avenue of hexosephosphate utilization in cell-free extracts. Pyruvate formation and utilization are discussed in relation to function and cofactor requirements.While phosphoglucose isomerase, aldolase, triosephosphate isomerase, and the enzymes converting phosphoglyceraldehyde to pyruvate are present and enzymatically active, phosphofructokinase appears to be the "bottleneck" to glycolysis. On the other hand fructose-1,6-diphosphate is oxidized by both DPN- and TPN-linked pathways, the latter through the efficient functioning of a specific phosphatase which forms fructose-6-phosphate readily. Glycolysis is considered to play only a very minor role in these extracts.A new "hexose cycle" for the metabolism of hexosephosphate is proposed. It consists of oxidation through "Zwischenferment", followed by the Entner–Doudoroff splitting system and resynthesis of hexosemonophosphate through reversal of the aldolase reaction followed by specific carbon-1 phosphate hydrolysis of fructose-1,6-diphosphate. The cycle is shown to be metabolically feasible and thermodynamically likely. It is considered to be the pathway by which cells which tend not to utilize the pentose cycle or classical glycolysis, but have an active 6-phosphogluconate-splitting system, metabolize hexosephosphate. Pyruvate produced as a result of the operation of this system is then oxidized via the tricarboxylic acid cycle in glucose-grown cells.

scholarly journals Carbon Sources Tune Antibiotic Susceptibility in Pseudomonas aeruginosa via Tricarboxylic Acid Cycle Control

2017 ◽  
Vol 24 (2) ◽  
pp. 195-206 ◽  
Author(s):  
Sylvain Meylan ◽  
Caroline B.M. Porter ◽  
Jason H. Yang ◽  
Peter Belenky ◽  
Arnaud Gutierrez ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Susceptibility ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Tricarboxylic Acid ◽  
Acid Cycle

The utilization of carbon sources by certain yeast strains

1951 ◽  
Vol 209 (1096) ◽  
pp. 142-142
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Glucose Metabolism ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Tricarboxylic Acid ◽  
Growth Characteristics ◽  
Acid Cycle ◽  
Yeast Strains ◽  
Carbon Substrates ◽  
Optimum Utilization

The growth characteristics of strains of Saccharomyces cerevisiae with different carbon substrates have been studied. The strains examined were able to grow with all the substrates tested, except for one aneurin-exacting strain which failed to metabolize oxalacetic, aconitic, citric and a -ketoglutaric acids. A daptation takes place upon successive subculturing in these substrates. The behaviour observed is compared with that of a typical bacterium, Bact. lactis aerogenes , in the same substrates. Training to some of the substrates may afford adaptation to certain other substrates. The relations found are not all in accordance with expectations based upon the tricarboxylic acid cycle. Some of the strains required training for optimum utilization of glucose. The effect of this training upon their behaviour in a first subculture into acids of the tricarboxylic acid fcycle has been examined. The use of the tricarboxylic acid cycle as a route for glucose metabolism in yeast is con­sidered in the light of the experimental evidence, and the conclusion is reached that this cycle is only one of two or more routes forming an interlocking network by means of which carbon sources can be metabolized in the organism.

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