Página 1 dos resultados de 1252 itens digitais encontrados em 0.014 segundos

Synergistic and Product Induction of the Enzymes of Tryptophan Metabolism in Pseudomonas acidovorans1

Rosenfeld, Henry; Feigelson, Philip
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1969 EN
Relevância na Pesquisa
692.0215%
The process of induction of tryptophan oxygenase in Pseudomonas acidovorans is typical of many microbial enzyme induction systems, in that it (i) requires cell multiplication and de novo protein synthesis, (ii) is subject to catabolite repression, (iii) results in the formation of a stable enzyme, whose level, upon removal of inducer, is diluted out by cell proliferation, and (iv) exhibits product induction. l-Kynurenine was more effective than l-tryptophan as an inducer of both tryptophan oxygenase and the second enzyme of the pathway, kynurenine formamidase. The occurrence of product induction of these two enzymes by their common metabolite eliminated the possibility of sequential induction of these enzymes. dl-5-Fluorotryptophan, nonmetabolizable and devoid of any inducing activity, resulted in a concentration-dependent inhibition of the l-tryptophan-mediated induction of tryptophan oxygenase; kynurenine formamidase induction, however, was not influenced by the presence of dl-5-fluorotryptophan. dl-7-Azatryptophan, also nonmetabolizable and completely inactive as an inducer, acted synergistically with l-tryptophan and superinduced tryptophan oxygenase levels. When induction was conducted in a medium containing only l-tryptophan and 7-azatryptophan as inducing agents...

Assimilation and Metabolism of Exogenous Organic Compounds by the Strict Autotrophs Thiobacillus thioparus and Thiobacillus neapolitanus

Johnson, Emmett J.; Abraham, S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1969 EN
Relevância na Pesquisa
786.92695%
The assimilation and utilization of the individual carbon atoms of pyruvate and acetate by cells of Thiobacillus thioparus and T. neapolitanus, in the presence and absence of an energy source, were studied by use of radioactive substrates. Both organisms produced 14CO2 from 14C-labeled pyruvate, but more came from carbon 1 than from carbons 2 or 3. The conversion of the carbons of acetate to CO2 by both organisms was much less than that from any of the pyruvate carbons. When labeled pyruvate and acetate were incubated with these organisms, small amounts of radioactivity were found in the tricholoacetic acid-soluble material, nucleic acids, and lipids, and larger amounts were found in the protein fraction. The composition of the incubation medium affected the amount of utilization and incorporation of labeled substrates by both organisms. The presence of an exogenous energy source (Na2S2O3) suppressed incorporation of the labeled substrates into various cellular components by T. thioparus, but enhanced incorporation by T. neapolitanus. When 14C-pyruvate was used as a substrate, as many as 12 radioactive compounds were found in the water-soluble fraction in the experiments with T. neapolitanus, whereas no more than three radioactive compounds were detected in this fraction in the experiments with T. thioparus. Of the total 14C activity found in the water-soluble fractions...

Phosphotransferase System of Staphylococcus aureus: Its Requirement for the Accumulation and Metabolism of Galactosides

Hengstenberg, Wolfgang; Penberthy, W. K.; Hill, Katherine L.; Morse, M. L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1969 EN
Relevância na Pesquisa
782.4641%
The phosphotransferase system of Staphylococcus aureus was characterized. Mutants defective in enzyme I and heat-stable (HPr) protein as well as in the two components specific to lactose accumulation, factor III and enzyme II, were isolated. Colorimetric assays for each of the components are presented based on the formation of o-nitrophenyl-β-d-galactoside-6-phosphate by the system and its hydrolysis by the staphylococcal 6-phospho-β-galactosidase. The components were partially purified and their molecular weights were estimated: enzyme I, 100,000 ± 15%; HPr, 10,000 ± 15%; factor III, 30,000 ± 15%; 6-phospho-β-galactosidase, 45,000. Enzyme II is a membrane-bound protein.

Erythritol Metabolism in Wild-Type and Mutant Strains of Schizophyllum commune

Braun, M. L.; Niederpruem, D. J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1969 EN
Relevância na Pesquisa
791.20055%
Erythritol uptake and metabolism were compared in wild-type mycelium and a dome morphological mutant of the wood-rotting mushroom Schizophyllum commune. Wild-type mycelium utilized glucose, certain hexitols, and pentitols including ribitol, as well as d-erythrose, erythritol, and glycerol as sole carbon sources for growth. The dome mutant utilized all of these compounds except d-erythrose and erythritol. Erythritol- or glycerol-grown wild-type mycelium incorporated erythritol into various cellular constituents, whereas glucose-grown cells lagged considerably before initiation of erythritol uptake. This acquisition was inhibited by cycloheximide. Dome mycelium showed behavior similar to wild-type in uptake of erythritol after growth on glucose or glycerol, except that erythritol was not further catabolized. Enzymes of carbohydrate metabolism were compared in cell extracts of glucose-cultured wild-type mycelium and dome. Enzymes of hexose monophosphate catabolism, nicotinamide adenine dinucleotide (NAD)-dependent sugar alcohol dehydrogenases, and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-coupled erythrose reductase were demonstrated in both. The occurrence of erythrose reductase was unaffected by the nature of the growth carbon source...

Lipids of Salmonella typhimurium and Escherichia coli: Structure and Metabolism

Ames, Giovanna F.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1968 EN
Relevância na Pesquisa
782.77875%
The nature and quantity of the phospholipids of Salmonella typhimurium and Escherichia coli K-12 have been examined. The main classes of phospholipids, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin have been completely characterized. Four minor compounds have been detected: phosphatidylserine, phosphatidic acid, and two partially characterized lipids. The phospholipid composition of the two organisms is quite similar, the only difference is the absence of one of the minor components and a decreased level of all components in E. coli. A study of the turnover of the phosphate in the phospholipids demonstrated no turnover in phosphatidylethanolamine, a slow turnover in phosphatidylglycerol, and a slow turnover in cardiolipin with, possibly, a transfer of phosphate from phosphatidylglycerol to cardiolipin. The amino acid phenylalanine is shown to become incorporated intact into lipidic compounds which have been partially characterized. Methods for the isolation and separation of lipids have been examined for their utility with these bacteria.

Physiology and Nutrition of Lampropedia hyalina

Puttlitz, Donald H.; Seeley, H. W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1968 EN
Relevância na Pesquisa
901.7894%
A detailed study of the physiology and nutrition of Lampropedia hyalina revealed that it is an aerobic, cytochrome-containing chemoheterotroph which is limited in its energy sources to a few intermediates (and close derivatives) of the Krebs cycle. Reducing compounds at low levels are potent growth inhibitors. The microbe has no photosynthetic ability (despite its previous taxonomic position with the sulfur purple bacteria). The results of a general investigation of its physiology are reported. Added biotin and thiamine are needed for growth in defined media; pantothenate is strongly stimulatory. Alanine, arginine, and tyrosine, as well as NH4Cl, serve as sole nitrogen sources. A unique motion exhibited by cells of a rapidly growing culture is described. Aspects of its metabolism of poly-β-hydroxybutyrate and limiting aspects of its physiology as related to its ecology are discussed.

Effect of Thiol-Binding Reagents on the Metabolism of Thiosulfate and Tetrathionate by Thiobacillus neapolitanus

Trudinger, P. A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1965 EN
Relevância na Pesquisa
692.29414%
Trudinger, P. A. (Division of Plant Industry, Canberra, Australia). Effect of thiol-binding reagents on the metabolism of thiosulfate and tetrathionate by Thiobacillus neapolitanus. J. Bacteriol. 89:617–625. 1965.—Iodoacetamide, N-ethyl maleimide (NEM), p-chloromercuribenzoate (CMB), Mercurochrome, and HgCl2 inhibited the oxidation of thiosulfate to sulfate by Thiobacillus neapolitanus; tetrathionate accumulated under these conditions. High concentrations of the thiol-binding reagents lowered the rate of oxidation of thiosulfate to tetrathionate; inhibition by CMB was reversed by high concentrations of thiosulfate. Relatively low concentrations of the thiol-binding reagents completely inhibited the oxidation and anaerobic metabolism of tetrathionate. Similar reagents had no effect on a soluble thiosulfate-oxidizing enzyme. Inhibition by thiol-binding reagents was overcome by washing the bacteria with Na2S or thioethanol after their exposure to the inhibitors. Under some conditions, the addition of thiosulfate or tetrathionate to bacterial suspensions before the addition of the thiol-binding reagents prevented the inhibition of thiosulfate and tetrathionate metabolism by these reagents. Thiosulfate catalyzed a rapid chemical breakdown of NEM and reacted with iodoacetamide. A complex between thiosulfate and mercuribenzoate was demonstrated. Three types of thiol group appear to be associated with the metabolism of thiosulfate and tetrathionate; one of these types may be located at the bacterial cell membrane. The results are consistent with the hypothesis that thiols (or disulfide groups) are binding sites for the substrates.

Pyruvate Metabolism, Carbon Dioxide Assimilation, and Nitrogen Fixation by an Achromobacter Species

Hamilton, I. R.; Burris, R. H.; Wilson, P. W.; Wang, C. H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1965 EN
Relevância na Pesquisa
691.1611%
Hamilton, I. R. (University of Wisconsin, Madison), R. H. Burris, P. W. Wilson, and C. H. Wang. Pyruvate metabolism and carbon dioxide assimilation by an Achromobacter species. J. Bacteriol. 89:647–653. 1965.—Carbon dioxide fixation by washed whole cells of Achromobacter N4-B has been observed during anaerobic pyruvate metabolism with both nitrogen- and NH4+-grown cells. Labeled sodium bicarbonate-C14 was assimilated into cells by a mechanism requiring pyruvate under conditions of nitrogen fixation, nitrogenase induction, and assimilation of NH4+. Of the assimilated radioactivity, 89% appeared in six amino acids and two ninhydrin-positive unknown compounds, with the distribution of the label essentially independent of the nitrogen nutritional state of the organism. Aspartic and glutamic acids were the most highly labeled, with lesser amounts in glycine, alanine, ornithine, arginine, and the unknowns. All of the radioactivity extracted from these cells by ethanol-boiling water appeared in a protein fraction precipitated by 20% trichloroacetic acid. Radiorespirometric experiments with individually labeled pyruvate substrates demonstrated the preferential decarboxylation of the C-1 of pyruvate by this organism in a flowing helium gas phase. This decarboxylation was almost completely inhibited by using flowing nitrogen in place of helium; the addition of 0.5% CO2 to the flowing nitrogen prevented inhibition and allowed 70% of the expected CO2 evolution. These results...

Polyol Metabolism in the Basidiomycete Schizophyllum commune

Niederpruem, Donald J.; Hafiz, Amtul; Henry, Lyle
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1965 EN
Relevância na Pesquisa
692.29414%
Niederpruem, Donald J. (Indiana University Medical Center, Indianapolis), Amtul Hafiz, and Lyle Henry. Polyol metabolism in the basidiomycete Schizophyllum commune. J. Bacteriol. 89:954–959. 1965.—The polyol metabolism of intact cells and extracts of the wood-rotting mushroom Schizophyllum commune was investigated during the developmental cycle. Exogenous polyols stimulated the cellular respiration of germlings, but were without effect on that of ungerminated basidiospores. Requisite enzymes of polyol metabolism were demonstrated in extracts of spores and of subsequent stages of development. Oxidation of mannitol and sorbitol appeared to be coupled to nicotinamide adenine dinucleotide (NAD) reduction and was favored in alkaline medium. Ketohexose formation was shown during mannitol oxidation, and the NAD-dependent oxidation of xylitol yielded ketopentose. Xylitol oxidation with nicotinamide adenine dinucleotide phosphate (NADP) as hydrogen acceptor led to pentose formation. Oxidation of reduced NAD was enhanced by fructose but not by sorbose. Reduction of aldohexose and pentose was dependent upon reduced NADP, and pentose reductase was maximal at pH 6.8. The specific activity of mannitol dehydrogenase was highest in extracts of vegetative mycelium. Growth in either glucose or xylose media had no significant effect on enzymes of polyol metabolism.

Glycine Synthesis and Metabolism in Escherichia coli

Pizer, Lewis I.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1965 EN
Relevância na Pesquisa
886.4238%
Pizer, Lewis I. (University of Pennsylvania, Philadelphia). Glycine synthesis and metabolism in Escherichia coli. J. Bacteriol. 89:1145–1150. 1965.—A correlation was demonstrated between a nutritional requirement that can only be satisfied by glycine and the absence of the enzymatic capacity to interconvert l-serine and glycine. Serine synthesis from 3-phosphoglycerate was observed in the same cell-free extracts which could not convert serine to glycine. The above results show that serine is the precursor of glycine under normal growth conditions. The C-2 of glycine provided “one-carbon” fragments when the C-3 of serine was not available as the source of “one-carbon” fragments. This condition occurred when a mutation produced a loss of serine aldolase activity or when a serine-glycine auxotroph was grown with glycine. Under these growth conditions, 30 to 40% of the “one-carbon” fragments used for cellular synthesis were derived from glycine.

Synthesis of Reserve Materials for Endogenous Metabolism in Streptococcus faecalis

Forrest, W. W.; Walker, D. J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1965 EN
Relevância na Pesquisa
691.4058%
Forrest, W. W. (University of Adelaide, Adelaide, South Australia), and D. J. Walker. Synthesis of reserve materials for endogenous metabolism in Streptococcus faecalis. J. Bacteriol. 89:1448–1452. 1965.—The growth curve of Streptococcus faecalis in batch culture with limited energy source shows an initial portion of exponential growth where the growth yield coefficient Yglucose is 32, followed by linear growth where Yglucose is 21. Endogenous metabolism is correlated with maintenance of glycolytic activity, and there is a marked change in the glycolytic activity of cells harvested under these conditions; however, endogenous metabolism cannot be detected in either case by measurement of the adenosine triphosphate (ATP) pool in the organisms. Cells harvested after growth with excess energy source exhibit endogenous metabolism, which is correlated with a much higher concentration of ATP in the organisms than occurs in the cells grown with limited energy source.

Glucose-C14 Metabolism of Dormant and Activated Ascospores of Neurospora

Budd, Kenneth; Sussman, Alfred S.; Eilers, Frederick I.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1966 EN
Relevância na Pesquisa
691.26375%
Budd, Kenneth (The University of Michigan, Ann Arbor), Alfred S. Sussman, and Frederick I. Eilers. Glucose-C14 metabolism of dormant and activated ascospores of Neurospora. J. Bacteriol. 91:551–561. 1966.—Dormant and activated ascospores of Neurospora tetrasperma, incubated in C14-labeled glucose, absorb and metabolize this sugar. At the same time, up to 55% of the CO2 production from endogenous substrates is quenched, whereas total CO2 production is unchanged. Glucose-carbon appears in CO2, lipids, and ethyl alcohol-soluble and -insoluble material in both dormant and activated ascospores, although the proportions entering these fractions differ in the two groups of spores. With few exceptions, the identifiable intermediates of glucose metabolism are the same in dormant and activated ascospores, indicating that the principal pathways may be identical. During glucose metabolism, dormant ascospores accumulate a nondialyzable, ethyl alcohol-soluble polymer, or polymers, which is either absent from activated spores or present in much smaller amounts. This material contains glucose, ribose, and at least nine amino acids, and may represent precursors of more complex cell material which accumulate because of an enzymatic deficiency in the dormant spore. Radioactivity is incorporated into all fractions of the dormant spores and into CO2 without a noticeable lag...

Carbon and Energy Sources for the Nitrifying Autotroph Nitrobacter

Delwiche, C. C.; Finstein, M. S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1965 EN
Relevância na Pesquisa
782.7232%
Delwiche, C. C. (University of California, Davis), and M. S. Finstein. Carbon and energy sources for the nitrifying autotroph Nitrobacter. J. Bacteriol. 90:102–107. 1965.—The effect of various organic compounds on the growth and metabolism of the obligatively autotrophic nitrifying organism Nitrobacter was studied. A slight stimulation of both nitrification and growth was obtainable with a number of organic amendments, including yeast extract, Vitamin Free Casamino Acids, and some amino acids. Depending upon culture conditions, a strong stimulation of growth was obtained with acetate as an amendment to the culture solution. Several compounds, including valine, hydroxyproline, and threonine, were inhibitory at concentrations of 10−3m. The incorporation of carbon from isotopically labeled organic compounds was demonstrated. Acetate and glycine were particularly strong contributors to cell carbons. These could not substitute for carbon dioxide as a sole carbon source for growth, however, nor could any other of the carbon compounds that were tried.

Oxidation and Assimilation of Carbohydrates by Micrococcus sodonensis1

Perry, Jerome J.; Evans, James B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1966 EN
Relevância na Pesquisa
782.8645%
Perry, Jerome J. (North Carolina State University, Raleigh), and James B. Evans. Oxidation and assimilation of carbohydrates by Micrococcus sodonensis. J. Bacteriol. 91:33–38. 1966.—Micrococcus sodonensis is a biotin-requiring strict aerobe that cannot utilize carbohydrates as sole sources of carbon and energy. However, addition of mannose, glucose, sucrose, or maltose to a medium on which the organism can grow resulted in an increase in total growth. M. sodonensis oxidized these sugars without induction, thus indicating the presence of constitutive enzymes for their transport, activation, and metabolism. Under appropriate nonproliferating cell conditions, glucose was readily incorporated into essential constituents of the cell. When glucose-1-C14 and glucose-6-C14 were oxidized by nonproliferating cells, the label was found in both the protein and nucleic acid fractions of the cell. The respiratory quotients of cells oxidizing glucose in saline and in phosphate buffer indicated assimilation of sugar carbon in buffer and virtually no assimilation in saline. The ability of M. sodonensis to completely oxidize glucose and to grow on intermediates of glucose oxidation but not on glucose suggests that glucose may suppress or repress some reaction(s) necessary for growth...

Susceptibility and Resistance of Several Fungi to Microbial Lysis1

Potgieter, H. J.; Alexander, M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1966 EN
Relevância na Pesquisa
692.0116%
Potgieter, H. J. (Cornell University, Ithaca, N.Y.), and M. Alexander. Susceptibility and resistance of several fungi to microbial lysis. J. Bacteriol. 91:1526–1532. 1966.—Strains of Streptomyces, Nocardia, and Pseudomonas capable of lysing hyphae of Fusarium solani or Neurospora crassa were obtained by selective culture, but attempts to isolate an organism lysing Rhizoctonia solani failed. When provided with F. solani or N. crassa as carbon sources, the actinomycetes tested produced β-(1 → 3) glucanase and chitinase. A mixture containing purified chitinase and β-(1 → 3) glucanase induced spheroplast formation in F. solani, caused some morphological changes in N. crassa, but had almost no effect on R. solani hyphae. The polysaccharides in R. solani walls, which contain a large amount of glucose as well as galactose, mannose, and glucosamine, were not hydrolyzed appreciably by the two enzymes. Laminaribiose and laminaritriose were released by enzymatic hydrolysis of F. solani and N. crassa walls, and gentiobiose was liberated from R. solani and N. crassa walls. Melaninlike materials were found in R. solani walls, accounting for 8.50% of the wall weight. A role for melanin in protecting hyphae from microbial lysis is suggested.

Physiology of Growth and Sporulation in Bacillus cereus I. Effect of Glutamic and Other Amino Acids

Buono, F.; Testa, R.; Lundgren, D. G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1966 EN
Relevância na Pesquisa
697.04914%
Buono, F. (Syracuse University, Syracuse, N.Y.), R. Testa, and D. G. Lundgren. Physiology of growth and sporulation in Bacillus cereus. I. Effect of glutamic and other amino acids. J. Bacteriol. 91:2291–2299. 1966.—Growth and sporulation were studied in Bacillus cereus by use of an active culture technique and a synthetic medium. A high level of glutamic acid (70 mm) was required for optimal growth and glucose oxidation followed by sporulation even though relatively little glutamic acid was consumed (14 mm). Optimal growth occurred with a combination of 14 mm glutamic acid and 56 mm (NH4)2SO4, aspartic acid, or alanine. Ornithine or arginine at 70 mm could replace glutamic acid in the synthetic medium without affecting the normal growth cycle. Glutamic acid was not replaced by any other amino acid, by (NH4)2SO4, or by a combination of either α-ketoglutarate or pyruvate plus (NH4)2SO4. Enzyme assays of cell-free extracts prepared from cells harvested at different times were used to study the metabolism of glutamic acid. Glutamic-oxaloacetic and glutamic-pyruvate transaminases were completely activated (or derepressed) during early stages of sporulation (period of 6 to 8 hr). Alanine dehydrogenase responded in a similar manner, but the levels of this enzyme were much higher throughout the culture cycle. Neither glutamic dehydrogenase nor α-ketoglutarate dehydrogenase was detected. Sporulation in a replacement salts medium was studied with cells harvested at different times from the synthetic medium. Cultures 2 to 6 hr old were unable to sporulate in the replacement salts medium unless glutamic acid (7.0 mm) was present. By the 6th hr...

Phosphorus Deprivation Responses and Phosphonate Utilization in a Thermophilic Synechococcus sp. from Microbial Mats▿ †

Adams, Melissa M.; Gómez-García, María R.; Grossman, Arthur R.; Bhaya, Devaki
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
696.669%
The genomes of two closely related thermophilic cyanobacterial isolates, designated Synechococcus isolate OS-A and Synechococcus isolate OS-B′, from the microbial mats of Octopus Spring (Yellowstone National Park) have been sequenced. An extensive suite of genes that are controlled by phosphate levels constitute the putative Pho regulon in these cyanobacteria. We examined physiological responses of an axenic OS-B′ isolate as well as transcript abundances of Pho regulon genes as the cells acclimated to phosphorus-limiting conditions. Upon imposition of phosphorus deprivation, OS-B′ stopped dividing after three to four doublings, and absorbance spectra measurements indicated that the cells had lost most of their phycobiliproteins and chlorophyll a. Alkaline phosphatase activity peaked and remained high after 48 h of phosphorus starvation, and there was an accumulation of transcripts from putative Pho regulon genes. Interestingly, the genome of Synechococcus isolate OS-B′ harbors a cluster of phn genes that are not present in OS-A isolates. The proteins encoded by the phn genes function in the transport and metabolism of phosphonates, which could serve as an alternative phosphorus source when exogenous phosphate is low. The phn genes were upregulated within a day of eliminating the source of phosphate from the medium. However...

Proline Availability Regulates Proline-4-Hydroxylase Synthesis and Substrate Uptake in Proline-Hydroxylating Recombinant Escherichia coli

Falcioni, Francesco; Blank, Lars M.; Frick, Oliver; Karau, Andreas; Bühler, Bruno; Schmid, Andreas
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/2013 EN
Relevância na Pesquisa
713.3084%
Microbial physiology plays a crucial role in whole-cell biotransformation, especially for redox reactions that depend on carbon and energy metabolism. In this study, regio- and enantio-selective proline hydroxylation with recombinant Escherichia coli expressing proline-4-hydroxylase (P4H) was investigated with respect to its interconnectivity to microbial physiology and metabolism. P4H production was found to depend on extracellular proline availability and on codon usage. Medium supplementation with proline did not alter p4h mRNA levels, indicating that P4H production depends on the availability of charged prolyl-tRNAs. Increasing the intracellular levels of soluble P4H did not result in an increase in resting cell activities above a certain threshold (depending on growth and assay temperature). Activities up to 5-fold higher were reached with permeabilized cells, confirming that host physiology and not the intracellular level of active P4H determines the achievable whole-cell proline hydroxylation activity. Metabolic flux analysis revealed that tricarboxylic acid cycle fluxes in growing biocatalytically active cells were significantly higher than proline hydroxylation rates. Remarkably, a catalysis-induced reduction of substrate uptake was observed...

Methylobacterium Genome Sequences: A Reference Blueprint to Investigate Microbial Metabolism of C1 Compounds from Natural and Industrial Sources

Vuilleumier, Stéphane; Chistoserdova, Ludmila; Bringel, Françoise; Lajus, Aurélie; Gourion, Benjamin; Barbe, Valérie; Chang, Jean; Cruveiller, Stéphane; Dossat, Carole; Gillett, Will; Gruffaz, Christelle; Haugen, Eric; Hourcade, Edith; Levy, Ruth; Ma
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
696.9897%
Methylotrophy describes the ability of organisms to grow on reduced organic compounds without carbon-carbon bonds. The genomes of two pink-pigmented facultative methylotrophic bacteria of the Alpha-proteobacterial genus Methylobacterium, the reference species Methylobacterium extorquens strain AM1 and the dichloromethane-degrading strain DM4, were compared. Methodology/Principal Findings The 6.88 Mb genome of strain AM1 comprises a 5.51 Mb chromosome, a 1.26 Mb megaplasmid and three plasmids, while the 6.12 Mb genome of strain DM4 features a 5.94 Mb chromosome and two plasmids. The chromosomes are highly syntenic and share a large majority of genes, while plasmids are mostly strain-specific, with the exception of a 130 kb region of the strain AM1 megaplasmid which is syntenic to a chromosomal region of strain DM4. Both genomes contain large sets of insertion elements, many of them strain-specific, suggesting an important potential for genomic plasticity. Most of the genomic determinants associated with methylotrophy are nearly identical, with two exceptions that illustrate the metabolic and genomic versatility of Methylobacterium. A 126 kb dichloromethane utilization (dcm) gene cluster is essential for the ability of strain DM4 to use DCM as the sole carbon and energy source for growth and is unique to strain DM4. The methylamine utilization (mau) gene cluster is only found in strain AM1...

Glucose and Gluconate Metabolism in a Mutant of Escherichia coli Lacking Gluconate-6-phosphate Dehydrase

Zablotny, R.; Fraenkel, D. G.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1967 EN
Relevância na Pesquisa
691.8929%
A mutant lacking gluconate-6-phosphate dehydrase (the first enzyme of the Entner-Doudoroff pathway) was isolated after ethyl methane sulfonate mutagenesis of Escherichia coli. Other enzymes of gluconate metabolism (gluconokinase, gluconate-6-phosphate dehydrogenase, and 2-keto-3-deoxygluconate-6-phosphate aldolase) were present in the mutant. When the mutant was grown on gluconate-1-14C, alanine isolated from protein was unlabeled, showing that the dehydrase was absent in vivo and that the sole pathway of gluconate metabolism in the mutant was the hexose monophosphate shunt. The mutant grew on gluconate with a doubling time of 155 min, compared with the parent strain's 56 min. On glucose and fructose it grew with normal doubling times. Thus, in E. coli, the Entner-Doudoroff pathway is used for gluconate metabolism but not for glucose metabolism.