scholarly journals Cation Transport in Escherichia coli

1962 ◽  
Vol 46 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Stanley G. Schultz ◽  
Wolfgang Epstein ◽  
David A. Goldstein
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
E Coli ◽  
Dense Suspension ◽  
K Concentration ◽  
Kinetics Of

The present study is concerned with the measurement of the unidirectional K flux in E. coli. Methods are described by means of which a fairly dense suspension of cells may be maintained in a well defined steady-state with respect to the intracellular K concentration and the pH of the medium. The kinetics of K42 exchange under these conditions are consistent with the presence of a single intracellular K compartment with a unidirectional K flux of 1 pmol/(cm2 sec.). This rate is independent of the extracellular K concentration over the range studied. The simultaneous rate of H secretion averages 16 pmols/(cm2 sec.) indicating that in the steady-state the efflux of metabolically produced H is not linked mole for mole to K movement.

scholarly journals Cation Transport in Escherichia coli

1963 ◽  
Vol 47 (2) ◽  
pp. 329-346 ◽  
Author(s):  
Stanley G. Schultz ◽  
Wolfgang Epstein ◽  
A. K. Solomon
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Cation Transport ◽  
Fresh Medium ◽  
Half Time ◽  
K Uptake ◽  
Acid Media ◽  
E Coli ◽  
K Concentration ◽  
Kinetics Of

The resuspension of K-poor, Na-rich stationary phase E. coli in fresh medium at pH 7.0 results in a rapid uptake of K and extrusion of Na by the cells. In all experiments net K uptake exceeded net Na extrusion. An investigation of the uptake of glucose, PO4, and Mg and the secretion of H by these cells indicates that the excess K uptake is not balanced by the simultaneous uptake of anions but must be accompanied by the extrusion of cations from the cell. The kinetics of net K uptake are consistent with the existence of two parallel influx processes. The first is rapid, of brief duration, and accounts for approximately 60 per cent of the total net K uptake. This process is a function of the extracellular K concentration, is inhibited in acid media, and appears to be a 1 for 1 exchange of extracellular K for intracellular H. The second influx process has a half-time of approximately 12 minutes, and is not affected by acid media. This process is a function of the intracellular Na concentration, is dependent upon the presence of K in the medium, and may be ascribed to a 1 for 1 exchange of extracellular K for intracellular Na.

scholarly journals Cation transport in Escherichia coli. IX. Regulation of K transport.

1978 ◽  
Vol 72 (3) ◽  
pp. 283-295 ◽  
Author(s):  
D B Rhoads ◽  
W Epstein
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
Transport Systems ◽  
Energy Requirements ◽  
Protonmotive Force ◽  
K Uptake ◽  
Kinetics Of ◽  
K Transport ◽  
External K

Kinetics of K exchange in the steady state and of net K uptake after osmotic upshock are reported for the four K transport systems of Escherichia coli: Kdp, TrkA, TrkD, and TrkF. Energy requirements for K exchange are reported for the Kdp and TrkA systems. For each system, kinetics of these two modes of K transport differ from those for net K uptake by K-depleted cells (Rhoads, D. B. F.B. Walters, and W. Epstein. 1976. J. Gen. Physiol. 67:325-341). The TrkA and TrkD systems are inhibited by high intracellular K, the TrkF system is stimulated by intracellular K, whereas the Kdp system is inhibited by external K when intracellular K is high. All four systems mediate net K uptake in response to osmotic upshock. Exchange by the Kdp and TrkA systems requires ATP but is not dependent on the protonmotive force. Energy requirements for the Kdp system are thus identical whether measured as net K uptake or K exchange, whereas the TrkA system differs in that it is dependent on the protonmotive force only for net K uptake. We suggest that in both the Kpd and TrkA systems formation of a phosphorylated intermediate is necessary for all K transport, although exchange transport may not consume energy. The protonmotive-force dependence of the TrkA system is interpreted as a regulatory influence, limiting this system to exchange except when the protonmotive force is high.

scholarly journals Cation Transport in Escherichia coli

1966 ◽  
Vol 49 (3) ◽  
pp. 469-481 ◽  
Author(s):  
Wolfgang Epstein ◽  
Stanley G. Schultz
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
Experimental Conditions ◽  
Tightly Coupled ◽  
K Concentration

K influx and net K flux have been measured in suspensions of chloramphenicol-arrested Escherichia coli. The rate of K exchange in the steady state was independent of the K concentration of the medium over a 200-fold range. Under a number of experimental conditions the rate of exchange may be considerably increased or decreased without changing the cellular K content. These results show that under these conditions changes in K influx are associated with equal changes in K efflux, and suggest that the latter process is, at least in part, both carrier-mediated and tightly coupled to the influx process.

Growth kinetics of Escherichia coli with galactose and several other sugars in carbon-limited chemostat culture

1999 ◽  
Vol 46 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Urs Lendenmann ◽  
Mario Snozzi ◽  
Thomas Egli
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Steady State ◽  
Specific Growth Rate ◽  
Growth Kinetics ◽  
Specific Growth ◽  
Chemostat Culture ◽  
Monod Model ◽  
E Coli ◽  
Kinetics Of

Kinetic models for microbial growth describe the specific growth rate (μ) as a function of the concentration of the growth-limiting nutrient (s) and a set of parameters. A typical example is the model proposed by Monod, where μ is related to s using substrate affinity (Ks) and the maximum specific growth rate (μmax). The preferred method to determine such parameters is to grow microorganisms in continuous culture and to measure the concentration of the growth-limiting substrate as a function of the dilution rate. However, owing to the lack of analytical methods to quantify sugars in the microgram per litre range, it has not been possible to investigate the growth kinetics of Escherichia coli in chemostat culture. Using an HPLC method able to determine steady-state concentrations of reducing sugars, we previously have shown that the Monod model adequately describes glucose-limited growth of E. coli ML30. This has not been confirmed for any other sugar. Therefore, we carried out a similar study with galactose and found steady-state concentrations between 18 and 840 μg·L-1 for dilution rates between 0.2 and 0.8·h-1, respectively. With these data the parameters of several models giving the specific growth rate as a function of the substrate concentration were estimated by nonlinear parameter estimation, and subsequently, the models were evaluated statistically. From all equations tested, the Monod model described the data best. The parameters for galactose utilisation were μmax = 0.75·h-1 and Ks = 67 μg·L-1. The results indicated that accurate Ks values can be estimated from a limited set of steady-state data when employing μmax measured during balanced growth in batch culture. This simplified procedure was applied for maltose, ribose, and fructose. For growth of E. coli with these sugars, μmax and Ks were for maltose 0.87·h-1, 100 μg·L-1; for ribose 0.57·h-1, 132 μg·L-1, and for fructose 0.70·h-1, 125 μg·L-1. Key words: monod model, continuous culture, galactose, glucose, fructose, maltose, ribose.

Effects of E. coli sepsis and myocardial depressant factor on interval-force relations in dog ventricle

1993 ◽  
Vol 264 (5) ◽  
pp. H1402-H1410 ◽  
Author(s):  
P. Jha ◽  
H. Jacobs ◽  
D. Bose ◽  
R. Wang ◽  
J. Yang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Calcium Metabolism ◽  
Calcium Content ◽  
Left Ventricular ◽  
Muscle Preparation ◽  
E Coli ◽  
Calcium Availability ◽  
Fractional Release

We examined whether depressed left ventricular (LV) contractility during Escherichia coli sepsis in dogs was due to a decrease in the fractional release of calcium from the sarcoplasmic reticulum (SR) or a reduction in calcium content in this organelle. To indirectly assess SR calcium availability in a right ventricular (RV) trabecular muscle preparation, we utilized functional indexes of cellular myocardial calcium metabolism, which included rapid-cooling contracture (RCC), an indicator of SR calcium content, and postrest contraction (PRC), an index of calcium availability from the release compartment of the SR. Measurements were made during steady-state stimulation at 0.5 and 1.5 Hz, during which time rest intervals of 30-240 s were periodically imposed. SR calcium availability was measured in RV trabeculae of dogs subjected to 4 h of E. coli sepsis and was compared with calcium availability measured in nonseptic dogs. We further characterized a filterable cardiodepressant substance (FCS), which has been previously shown to be associated with LV depression in this model, to determine whether it produced changes in calcium metabolism similar to those found in sepsis. The results showed that calcium availability from the SR of septic dogs was not impaired. Furthermore, FCS was found in the 10,000- to 30,000-mol wt fraction of plasma and produced changes in PRC in canine trabeculae that were similar to those produced during sepsis. We conclude that, as assessed by PRC and RCC, SR calcium content and release are not impaired in sepsis.

Inactivation of Escherichia coli by Ultrasound Combined with Nisin

2018 ◽  
Vol 81 (6) ◽  
pp. 993-1000 ◽  
Author(s):  
ZUWEN WANG ◽  
XIUFANG BI ◽  
RUI XIANG ◽  
LIYI CHEN ◽  
XIAOPING FENG ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Synergistic Effect ◽  
Linear Models ◽  
Treatment Time ◽  
Nutrient Broth ◽  
Inactivation Kinetics ◽  
Growth Phases ◽  
E Coli ◽  
Kinetics Of ◽  
Inactivation Effect

ABSTRACT The aim of this study was to investigate the inactivation of nonpathogenic Escherichia coli in nutrient broth and milk through the use of either ultrasound (US) alone or US combined with nisin (US + nisin) treatments. The E. coli cells were treated at 0 to 55°C, 242.04 to 968.16 W/cm2 for 0 to 15 min. The results showed that the inactivation of E. coli by US and US + nisin increased when the temperature, US power density, and treatment time were increased. The inactivation kinetics of E. coli in nutrient broth by US and US + nisin both conformed to linear models. The largest reductions of 2.89 and 2.93 log cycles by US and US + nisin, respectively, were achieved at 968.16 W/cm2 and at 25°C for 15 min. The suspension media of the E. coli cells influenced the inactivation effect of US, while the growth phases of E. coli cells did not affect their resistance to US. Under all experiment conditions of this study, the differences between US and US + nisin in their respective inactivation effects on E. coli were not obvious. The results suggested that nisin had either no effect at all or a weak synergistic effect with US and that the E. coli cells were inactivated mainly by US, thus indicating that the inactivation of E. coli by US is an “all or nothing” event.

Viability of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in Yellow Fat Spreads as Affected by Storage Temperature

2003 ◽  
Vol 66 (4) ◽  
pp. 549-558 ◽  
Author(s):  
SARAH L. HOLLIDAY ◽  
LARRY R. BEUCHAT
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Storage Temperature ◽  
Salt Content ◽  
Inactivation Kinetics ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Inhibition Of Growth ◽  
Time Required ◽  
Kinetics Of

A study was conducted to characterize the survival and inactivation kinetics of a five-serotype mixture of Salmonella (6.23 to 6.55 log10 CFU per 3.5-ml or 4-g sample), a five-strain mixture of Escherichia coli O157:H7 (5.36 to 6.14 log10 CFU per 3.5-ml or 4-g sample), and a six-strain mixture of Listeria monocytogenes (5.91 to 6.18 log10 CFU per 3.5-ml or 4-g sample) inoculated into seven yellow fat spreads (one margarine, one butter-margarine blend, and five dairy and nondairy spreads and toppings) after formulation and processing and stored at 4.4, 10, and 21°C for up to 94 days. Neither Salmonella nor E. coli O157:H7 grew in any of the test products. The time required for the elimination of each pathogen depended on the product and the storage temperature. Death was more rapid at 21°C than at 4.4 or 10°C. Depending on the product, the time required for the elimination of viable cells at 21°C ranged from 5 to 7 days to >94 days for Salmonella, from 3 to 5 days to 28 to 42 days for E. coli O157:H7, and from 10 to 14 days to >94 days for L. monocytogenes. Death was most rapid in a water-continuous spray product (pH 3.66, 4.12% salt) and least rapid in a butter-margarine blend (pH 6.66, 1.88% salt). E. coli O157:H7 died more rapidly than did Salmonella or L. monocytogenes regardless of storage temperature. Salmonella survived longer in high-fat (≥61%) products than in products with lower fat contents. The inhibition of growth is attributed to factors such as acidic pH, salt content, the presence of preservatives, emulsion characteristics, and nutrient deprivation. L. monocytogenes did not grow in six of the test products, but its population increased between 42 and 63 days in a butter-margarine blend stored at 10°C and between 3 and 7 days when the blend was stored at 21°C. On the basis of the experimental parameters examined in this study, traditional margarine and spreads not containing butter are not “potentially hazardous foods” in that they do not support the growth of Salmonella, E. coli O157:H7, or L. monocytogenes.

scholarly journals Escherichia coli alkaline phosphatase. Kinetic studies with the tetrameric enzyme

1972 ◽  
Vol 126 (5) ◽  
pp. 1081-1090 ◽  
Author(s):  
S. E. Halford ◽  
M. J. Schlesinger ◽  
H. Gutfreund
Keyword(s):  
Escherichia Coli ◽  
Alkaline Phosphatase ◽  
Steady State ◽  
Analytical Ultracentrifugation ◽  
Kinetic Studies ◽  
Product Formation ◽  
E Coli ◽  
Enzyme Subunits ◽  
Self Association ◽  
The Stability

1. The stability of the tetrameric form of Escherichia coli alkaline phosphatase was examined by analytical ultracentrifugation. 2. The stopped-flow technique was used to study the hydrolysis of nitrophenyl phosphates by the alkaline phosphatase tetramer at pH7.5 and 8.3. In both cases transient product formation was observed before the steady state was attained. Both transients consisted of the liberation of 1mol of nitrophenol/2mol of enzyme subunits within the dead-time of the apparatus. The steady-state rates were identical with those observed with the dimer under the same conditions. 3. The binding of 2-hydroxy-5-nitrobenzyl phosphonate to the alkaline phosphatase tetramer was studied by the temperature-jump technique. The self-association of two dimers to form the tetramer is linked to a conformation change within the dimer. This accounts for the differences between the transient phases in the reactions of the dimer and the tetramer with substrate. 4. Addition of Pi to the alkaline phosphatase tetramer caused it to dissociate into dimers. The tetramer is unable to bind this ligand. It is suggested that the tetramer undergoes a compulsory dissociation before the completion of its first turnover with substrate. 5. On the basis of these findings a mechanism is proposed for the involvement of the alkaline phosphatase tetramer in the physiology of E. coli.

scholarly journals Chorismate synthase. Pre-steady-state kinetics of phosphate release from 5-enolpyruvylshikimate 3-phosphate

1990 ◽  
Vol 265 (3) ◽  
pp. 899-902 ◽  
Author(s):  
T R Hawkes ◽  
T Lewis ◽  
J R Coggins ◽  
D M Mousdale ◽  
D J Lowe ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Lag Phase ◽  
Chorismate Synthase ◽  
Phosphate Release ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Steady State Kinetics ◽  
Rate Limiting ◽  
Kinetics Of

The pre-steady-state kinetics of phosphate formation from 5-enolpyruvylshikimate 3-phosphate catalysed by Escherichia coli chorismate synthase (EC 4.6.1.4) were studied by a rapid-acid-quench technique at 25 degrees C at pH 7.5. No pre-steady-state ‘burst’ or ‘lag’ phase was observed, showing that phosphate is released concomitant with the rate-limiting step of the enzyme. The implications of this result for the mechanism of action of chorismate synthase are discussed.

scholarly journals Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense

2006 ◽  
Vol 188 (13) ◽  
pp. 4759-4768 ◽  
Author(s):  
Bonnie B. Stephens ◽  
Star N. Loar ◽  
Gladys Alexandre
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Azospirillum Brasilense ◽  
Model Organism ◽  
Spatial Gradient ◽  
Wild Type ◽  
Temporal Gradient ◽  
E Coli ◽  
Significant Difference

ABSTRACT It has previously been reported that the alpha-proteobacterium Azospirillum brasilense undergoes methylation-independent chemotaxis; however, a recent study revealed cheB and cheR genes in this organism. We have constructed cheB, cheR, and cheBR mutants of A. brasilense and determined that the CheB and CheR proteins under study significantly influence chemotaxis and aerotaxis but are not essential for these behaviors to occur. First, we found that although cells lacking CheB, CheR, or both were no longer capable of responding to the addition of most chemoattractants in a temporal gradient assay, they did show a chemotactic response (albeit reduced) in a spatial gradient assay. Second, in comparison to the wild type, cheB and cheR mutants under steady-state conditions exhibited an altered swimming bias, whereas the cheBR mutant and the che operon mutant did not. Third, cheB and cheR mutants were null for aerotaxis, whereas the cheBR mutant showed reduced aerotaxis. In contrast to the swimming bias for the model organism Escherichia coli, the swimming bias in A. brasilense cells was dependent on the carbon source present and cells released methanol upon addition of some attractants and upon removal of other attractants. In comparison to the wild type, the cheB, cheR, and cheBR mutants showed various altered patterns of methanol release upon exposure to attractants. This study reveals a significant difference between the chemotaxis adaptation system of A. brasilense and that of the model organism E. coli and suggests that multiple chemotaxis systems are present and contribute to chemotaxis and aerotaxis in A. brasilense.

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