Participation of the Entner–Doudoroff pathway inEscherichia colistrains with an inactive phosphotransferase system (PTS–Glc+) in gluconate and glucose batch cultures

2005 ◽  
Vol 51 (11) ◽  
pp. 975-982 ◽  
Author(s):  
Elizabeth Ponce ◽  
Mauricio García ◽  
Ma. Enriqueta Muñoz
Keyword(s):  
Escherichia Coli ◽  
Pyruvate Kinase ◽  
Specific Growth ◽  
Metabolic Response ◽  
Gene Knockout ◽  
Phosphotransferase System ◽  
Batch Cultures ◽  
Consumption Rates ◽  
Pyruvate Kinase Isoenzymes ◽  
Specific Growth Rates

The activity of the enzymes of the central metabolic pathways has been the subject of intensive analysis; however, the Entner–Doudoroff (ED) pathway has only recently begun to attract attention. The metabolic response to edd gene knockout in Escherichia coli JM101 and PTS–Glc+was investigated in gluconate and glucose batch cultures and compared with other pyruvate kinase and PTS mutants previously constructed. Even though the specific growth rates between the strain carrying the edd gene knockout and its parent JM101 and PTS–Glc+edd and its parent PTS–Glc+were very similar, reproducible changes in the specific consumption rates and biomass yields were obtained when grown on glucose. These results support the participation of the ED pathway not only on gluconate metabolism but on other metabolic and biochemical processes in E. coli. Despite that gluconate is a non-PTS carbohydrate, the PTS–Glc+and derived strains showed important reductions in the specific growth and gluconate consumption rates. Moreover, the overall activity of the ED pathway on gluconate resulted in important increments in PTS–Glc+and PTS-Glc+pykF mutants. Additional results obtained with the pykA pykF mutant indicate the important contribution of the pyruvate kinase enzymes to pyruvate synthesis and energy production in both carbon sources.Key words: Escherichia coli, gluconate metabolism, Entner-Doudoroff pathway, PT system, pyruvate kinase isoenzymes.

Effects of turbidity on prey consumption and growth in brook trout and implications for bioenergetics modeling

2001 ◽  
Vol 58 (2) ◽  
pp. 386-393 ◽  
Author(s):  
John A Sweka ◽  
Kyle J Hartman
Keyword(s):  
Growth Rates ◽  
Brook Trout ◽  
Specific Growth ◽  
Abiotic Factors ◽  
Foraging Strategies ◽  
Turbid Water ◽  
Daily Consumption ◽  
Consumption Rates ◽  
The Difference ◽  
Specific Growth Rates

Brook trout (Salvelinus fontinalis) were held in an artificial stream to observe the influence of turbidity on mean daily consumption and specific growth rates. Treatment turbidity levels ranged from clear (<3.0 nephelometric turbidity units (NTU)) to very turbid water (> 40 NTU). Observed mean daily specific consumption rates were standardized to the mean weight of all brook trout tested. Turbidity had no significant effect on mean daily consumption, but specific growth rates decreased significantly as turbidity increased. Brook trout in turbid water became more active and switched foraging strategies from drift feeding to active searching. This switch was energetically costly and resulted in lower specific growth rates in turbid water as compared with clear water. Bioenergetics simulations were run to compare observed growth with that predicted by the model. Observed growth values fell below those predicted by the model and the difference increased as turbidity increased. Abiotic factors, such as turbidity, which bring about changes in the activity rates of fish, can have implications for the accuracy of predicted growth by bioenergetics models.

Influence of specific growth rate over the secretory expression of recombinant potato carboxypeptidase inhibitor in fed-batch cultures of Escherichia coli

2010 ◽  
Vol 45 (8) ◽  
pp. 1334-1341 ◽  
Author(s):  
Juan-Miguel Puertas ◽  
Jordi Ruiz ◽  
Mónica Rodríguez de la Vega ◽  
Julia Lorenzo ◽  
Glòria Caminal ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Fed Batch ◽  
Secretory Expression ◽  
Batch Cultures ◽  
Carboxypeptidase Inhibitor

scholarly journals Catalase Overexpression Reduces Lactic Acid-Induced Oxidative Stress in Saccharomyces cerevisiae

2009 ◽  
Vol 75 (8) ◽  
pp. 2320-2325 ◽  
Author(s):  
Derek A. Abbott ◽  
Erwin Suir ◽  
Giang-Huong Duong ◽  
Erik de Hulster ◽  
Jack T. Pronk ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Reference Strain ◽  
Specific Growth ◽  
Pyruvate Decarboxylase ◽  
Additional Stress ◽  
Batch Cultures ◽  
Native Promoter ◽  
Specific Growth Rates ◽  
Increased Activity

ABSTRACT Industrial production of lactic acid with the current pyruvate decarboxylase-negative Saccharomyces cerevisiae strains requires aeration to allow for respiratory generation of ATP to facilitate growth and, even under nongrowing conditions, cellular maintenance. In the current study, we observed an inhibition of aerobic growth in the presence of lactic acid. Unexpectedly, the cyb2Δ reference strain, used to avoid aerobic consumption of lactic acid, had a specific growth rate of 0.25 h−1 in anaerobic batch cultures containing lactic acid but only 0.16 h−1 in identical aerobic cultures. Measurements of aerobic cultures of S. cerevisiae showed that the addition of lactic acid to the growth medium resulted in elevated levels of reactive oxygen species (ROS). To reduce the accumulation of lactic acid-induced ROS, cytosolic catalase (CTT1) was overexpressed by replacing the native promoter with the strong constitutive TPI1 promoter. Increased activity of catalase was confirmed and later correlated with decreased levels of ROS and increased specific growth rates in the presence of high lactic acid concentrations. The increased fitness of this genetically modified strain demonstrates the successful attenuation of additional stress that is derived from aerobic metabolism and may provide the basis for enhanced (micro)aerobic production of organic acids in S. cerevisiae.

scholarly journals Pyruvate Kinase-Deficient Escherichia coli Exhibits Increased Plasmid Copy Number and Cyclic AMP Levels

2009 ◽  
Vol 191 (9) ◽  
pp. 3041-3049 ◽  
Author(s):  
Drew S. Cunningham ◽  
Zhu Liu ◽  
Nathan Domagalski ◽  
Richard R. Koepsel ◽  
Mohammad M. Ataai ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cyclic Amp ◽  
Pyruvate Kinase ◽  
Copy Number ◽  
Plasmid Copy Number ◽  
Phosphotransferase System ◽  
Plasmid Copy ◽  
Copy Numbers ◽  
High Copy Number Plasmid ◽  
Pathway Flux

ABSTRACT Previously established consequences of abolishing pyruvate kinase (Pyk) activity in Escherichia coli during aerobic growth on glucose include reduced acetate production, elevated hexose monophosphate (HMP) pathway flux, elevated phosphoenolpyruvate carboxylase (Ppc) flux, and an increased ratio of phosphoenolpyruvate (PEP) to pyruvate. These traits inspired two hypotheses. First, the mutant (PB25) may maintain more plasmid than the wild type (JM101) by combining traits reported to facilitate plasmid DNA synthesis (i.e., decreased Pyk flux and increased HMP pathway and Ppc fluxes). Second, PB25 likely possesses a higher level of cyclic AMP (cAMP) than JM101. This is based on reports that connect elevated PEP/pyruvate ratios to phosphotransferase system signaling and adenylate cyclase activation. To test the first hypothesis, the strains were transformed with a pUC-based, high-copy-number plasmid (pGFPuv), and copy numbers were measured. PB25 exhibited a fourfold-higher copy number than JM101 when grown at 37°C. At 42°C, its plasmid content was ninefold higher than JM101 at 37°C. To test the second hypothesis, cAMP was measured, and the results confirmed it to be higher in PB25 than JM101. This elevation was not enough to elicit a strong regulatory effect, however, as indicated by the comparative expression of the pGFPuv-based reporter gene, gfp uv , under the control of the cAMP-responsive lac promoter. The elevated cAMP in PB25 suggests that Pyk may participate in glucose catabolite repression by serving among all of the factors that tighten gene expression.

Specific growth rate and not cell density controls the general stress response in Escherichia coli

Microbiology ◽  
2004 ◽  
Vol 150 (6) ◽  
pp. 1637-1648 ◽  
Author(s):  
Julian Ihssen ◽  
Thomas Egli
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Stress Response ◽  
Specific Growth Rate ◽  
Cell Density ◽  
Specific Growth ◽  
Batch Cultures ◽  
General Stress Response ◽  
E Coli ◽  
Density Effects

In batch cultures of Escherichia coli, the intracellular concentration of the general stress response sigma factor RpoS typically increases during the transition from the exponential to the stationary growth phase. However, because this transition is accompanied by complex physico-chemical and biological changes, which signals predominantly elicit this induction is still the subject of debate. Careful design of the growth environment in chemostat and batch cultures allowed the separate study of individual factors affecting RpoS. Specific growth rate, and not cell density or the nature of the growth-limiting nutrient, controlled RpoS expression and RpoS-dependent hydroperoxidase activity. Furthermore, it was demonstrated that the standard E. coli minimal medium A (MMA) is not suitable for high-cell-density cultivation because it lacks trace elements. Previously reported cell-density effects in chemostat cultures of E. coli can be explained by a hidden, secondary nutrient limitation, which points to the importance of medium design and appropriate experimental set-up for studying cell-density effects.

Quantitative relationships for specific growth rates and macromolecular compositions of Mycobacterium tuberculosis, Streptomyces coelicolor A3(2) and Escherichia coli B/r: an integrative theoretical approach

Microbiology ◽  
2004 ◽  
Vol 150 (5) ◽  
pp. 1413-1426 ◽  
Author(s):  
Robert A. Cox
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Mycobacterium Tuberculosis ◽  
Growth Rates ◽  
Specific Growth ◽  
Streptomyces Coelicolor ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
E Coli ◽  
Specific Growth Rates

Further understanding of the physiological states of Mycobacterium tuberculosis and other mycobacteria was sought through comparisons with the genomic properties and macromolecular compositions of Streptomyces coelicolor A3(2), grown at 30 °C, and Escherichia coli B/r, grown at 37 °C. A frame of reference was established based on quantitative relationships observed between specific growth rates (μ) of cells and their macromolecular compositions. The concept of a schematic cell based on transcription/translation coupling, average genes and average proteins was developed to provide an instantaneous view of macromolecular synthesis carried out by cells growing at their maximum rate. It was inferred that the ultra-fast growth of E. coli results from its ability to increase the average number of rRNA (rrn) operons per cell through polyploidy, thereby increasing its capacity for ribosome synthesis. The maximum growth rate of E. coli was deduced to be limited by the rate of uptake and consumption of nutrients providing energy. Three characteristic properties of S. coelicolor A3(2) growing optimally (μ=0·30 h−1) were identified. First, the rate of DNA replication was found to approach the rate reported for E. coli (μ=1·73 h−1); secondly, all rrn operons were calculated to be fully engaged in precursor-rRNA synthesis; thirdly, compared with E. coli, protein synthesis was found to depend on higher concentrations of ribosomes and lower concentrations of aminoacyl-tRNA and EF-Tu. An equation was derived for E. coli B/r relating μ to the number of rrn operons per genome. Values of μ=0·69 h−1 and μ=1·00 h−1 were obtained respectively for cells with one or two rrn operons per genome. Using the author's equation relating the number of rrn operons per genome to maximum growth rate, it is expected that M. tuberculosis with one rrn operon should be capable of growing much faster than it actually does. Therefore, it is suggested that the high number of insertion sequences in this species attenuates growth rate to still lower values.

scholarly journals Microbial evolution in a simple unstructured environment: genetic differentiation in Escherichia coli.

Genetics ◽  
1994 ◽  
Vol 137 (4) ◽  
pp. 903-917 ◽  
Author(s):  
R F Rosenzweig ◽  
R R Sharp ◽  
D S Treves ◽  
J Adams
Keyword(s):  
Escherichia Coli ◽  
Structural Changes ◽  
Specific Growth ◽  
Microbial Evolution ◽  
Kinetics Analysis ◽  
Acetyl Coenzyme A ◽  
Unstructured Environment ◽  
Single Clone ◽  
Glycerol Uptake ◽  
Specific Growth Rates

Abstract Populations of Escherichia coli initiated with a single clone and maintained for long periods in glucose-limited continuous culture, become polymorphic. In one population, three clones were isolated and by means of reconstruction experiments were shown to be maintained in stable polymorphism, although they exhibited substantial differences in maximum specific growth rates and in glucose uptake kinetics. Analysis of these three clones revealed that their stable coexistence could be explained by differential patterns of the secretion and uptake of two alternative metabolites acetate and glycerol. Regulatory (constitutive and null) mutations in acetyl-coenzyme A synthetase accounted for different patterns of acetate secretion and uptake seen. Altered patterns in glycerol uptake are most likely explained by mutations which result in quantitative differences in the induction of the glycerol regulon and/or structural changes in glycerol kinase that reduce allosteric inhibition by effector molecules associated with glycolysis. The evolution of resource partitioning, and consequent polymorphisms which arise may illustrate incipient processes of speciation in asexual organisms.

scholarly journals Food Consumption and Growth Rates of Juvenile Black Carp Fed Natural and Prepared Feeds

2014 ◽  
Vol 5 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Nathaniel C. Hodgins ◽  
Harold L. Schramm ◽  
Patrick D. Gerard
Keyword(s):  
Food Consumption ◽  
Growth Rates ◽  
Specific Growth ◽  
Daily Consumption ◽  
Black Carp ◽  
Consumption Rates ◽  
Wet Weight ◽  
Feeding Trials ◽  
Specific Growth Rates ◽  
Weight Number

Abstract The introduced mollusciphagic black carp Mylopharyngodon piceus poses a significant threat to native mollusks in temperate waters throughout the northern hemisphere, but consumption rates necessary to estimate the magnitude of impact on mollusks have not been established. We measured food consumption and growth rates for small (77–245 g) and large (466–1,071 g) triploid black carp held individually under laboratory conditions at 20, 25, and 30°C. Daily consumption rates (g food · g wet weight fish−1·d−1·100) of black carp that received prepared feed increased with temperature (small black carp 1.39–1.71; large black carp 1.28–2.10), but temperature-related increases in specific growth rate (100[ln(final weight) - ln(initial weight)]/number of days) only occurred for the large black carp (small black carp −0.02 to 0.19; large black carp 0.16–0.65). Neither daily consumption rates (5.90–6.28) nor specific growth rates (0.05–0.24) differed among temperatures for small black carp fed live snails. The results of these laboratory feeding trials indicate food consumption rates can vary from 289.9 to 349.5 J·g−1·d−1 for 150 g black carp receiving prepared feed, from 268.8 to 441.0 J·g−1·d−1for 800 g black carp receiving prepared feed, and from 84.8 to 90.2 J·g−1·d−1 for 150 g black carp that feed on snails. Applying estimated daily consumption rates to estimated biomass of native mollusks indicates that a relatively low biomass of black carp could eliminate native snails and substantially reduce recruitment of mussels in time periods as short as 180 d.

scholarly journals PafR, a Novel Transcription Regulator, Is Important for Pathogenesis in Uropathogenic Escherichia coli

2014 ◽  
Vol 82 (10) ◽  
pp. 4241-4252 ◽  
Author(s):  
Mordechai Baum ◽  
Mobarak Watad ◽  
Sara N. Smith ◽  
Christopher J. Alteri ◽  
Noa Gordon ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Biofilm Formation ◽  
Gene Knockout ◽  
Sensory System ◽  
Phosphotransferase System ◽  
Knockout Mutant ◽  
Double Knockout ◽  
Content Type

ABSTRACTThemetVgenomic island in the chromosome of uropathogenicEscherichia coli(UPEC) encodes a putative transcription factor and a sugar permease of the phosphotransferase system (PTS), which are predicted to compose a Bgl-like sensory system. The presence of these two genes, hereby termedpafRandpafP, respectively, has been previously shown to correlate with isolates causing clinical syndromes. We show here that deletion of both genes impairs the ability of the resulting mutant to infect the CBA/J mouse model of ascending urinary tract infection compared to that of the parent strain, CFT073. Expressing the two genes intransin the two-gene knockout mutant complemented full virulence. Deletion of either gene individually generated the same phenotype as the double knockout, indicating that bothpafRandpafPare important to pathogenesis. We screened numerous environmental conditions but failed to detect expression from the promoter that precedes thepafgenesin vitro, suggesting that they arein vivoinduced (ivi). Although PafR is shown here to be capable of functioning as a transcriptional antiterminator, its targets in the UPEC genome are not known. Using microarray analysis, we have shown that expression of PafR from a heterologous promoter in CFT073 affects expression of genes related to bacterial virulence, biofilm formation, and metabolism. Expression of PafR also inhibits biofilm formation and motility. Taken together, our results suggest that thepafgenes are implicated in pathogenesis and that PafR controls virulence genes, in particular biofilm formation genes.

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