scholarly journals Active accumulation of tetracycline by Escherichia coli

1970 ◽  
Vol 116 (2) ◽  
pp. 287-297 ◽  
Author(s):  
T. J. Franklin ◽  
B. Higginson
Keyword(s):  
Escherichia Coli ◽  
High Speed ◽  
Osmotic Shock ◽  
Significant Proportion ◽  
Supernatant Fraction ◽  
High Concentration ◽  
Temperature Dependent ◽  
Experimental Conditions ◽  
E Coli ◽  
Macromolecular Component

1. At low concentrations of tetracycline (10μg/ml) net accumulation of the drug by Escherichia coli cells ceased after 7–10min. 2. At higher concentrations of tetracycline (>30μg/ml) the period of net accumulation of the drug was significantly extended. 3. The efflux of tetracycline from E. coli cells transferred from medium containing 10μg of tetracycline/ml to drug-free medium was a rapid temperature-dependent process and was accelerated by 2,4-dinitrophenol. 4. As the concentration of tetracycline in the preloading phase was increased, the rate of subsequent efflux of the drug progressively declined. The efflux of drug from cells preloaded in medium containing 200μg of tetracycline/ml was negligible, although efflux was readily provoked by 2,4-dinitrophenol, by N-ethylmaleimide or by omission of glucose from the medium. 5. The initial rate of uptake of tetracycline by E. coli cells was linearly proportional to the concentration of tetracycline in the medium up to the maximum concentration of drug obtainable under the experimental conditions used (400μg/ml, 0.83mm). 6. Although N-ethylmaleimide strongly inhibited the accumulation of tetracycline by E. coli, no evidence was obtained for the direct involvement of thiol groups in the transport process. It was concluded that N-ethylmaleimide inhibited accumulation by interruption of the energy supply of the cells. 7. Osmotic shock of E. coli cells did not significantly affect the influx of tetracycline, but promoted both efflux of tetracycline and cell lysis in cells treated with a high concentration of tetracycline. 8. A study of the distribution of tetracycline among the subcellular fractions of penicillin-induced spheroplasts preincubated with various concentrations of tetracycline indicated that 60–70% of the accumulated tetracycline was in the high-speed supernatant fraction. Sephadex chromatography showed that the tetracycline of this fraction was present as the free drug. Sephadex chromatography of a detergent extract of the membrane fraction, however, indicated that a significant proportion of the tetracycline radioactivity of this fraction was apparently bound to some macromolecular component. 9. Cellulose phosphate paper chromatography of cold-acid extracts of spheroplasts preloaded with tetracycline indicated that the accumulated drug was chemically unchanged. 10. Membrane preparations isolated from osmotically lysed penicillin-induced spheroplasts showed a temperature-dependent binding of tetracycline that was not energy-dependent and was not inhibited by N-ethylmaleimide. The binding process was stimulated by omitting Mg2+ from the medium, but conversely was profoundly inhibited by EDTA. 11. The relevance of these findings to the probable mechanism of active tetracycline accumulation by E. coli is discussed.

scholarly journals In Escherichia coli Ammonia Inhibits Cytochrome bo3 But Activates Cytochrome bd-I

Antioxidants ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 13
Author(s):  
Elena Forte ◽  
Sergey A. Siletsky ◽  
Vitaliy B. Borisov
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Dissociation Constants ◽  
Reductase Activity ◽  
Ammonia Concentration ◽  
High Concentration ◽  
E Coli ◽  
Cytochrome Bd ◽  
Cytochrome Bo3 ◽  
Oxygen Reductase

Interaction of two redox enzymes of Escherichia coli, cytochrome bo3 and cytochrome bd-I, with ammonium sulfate/ammonia at pH 7.0 and 8.3 was studied using high-resolution respirometry and absorption spectroscopy. At pH 7.0, the oxygen reductase activity of none of the enzymes is affected by the ligand. At pH 8.3, cytochrome bo3 is inhibited by the ligand, with 40% maximum inhibition at 100 mM (NH4)2SO4. In contrast, the activity of cytochrome bd-I at pH 8.3 increases with increasing the ligand concentration, the largest increase (140%) is observed at 100 mM (NH4)2SO4. In both cases, the effector molecule is apparently not NH4+ but NH3. The ligand induces changes in absorption spectra of both oxidized cytochromes at pH 8.3. The magnitude of these changes increases as ammonia concentration is increased, yielding apparent dissociation constants Kdapp of 24.3 ± 2.7 mM (NH4)2SO4 (4.9 ± 0.5 mM NH3) for the Soret region in cytochrome bo3, and 35.9 ± 7.1 and 24.6 ± 12.4 mM (NH4)2SO4 (7.2 ± 1.4 and 4.9 ± 2.5 mM NH3) for the Soret and visible regions, respectively, in cytochrome bd-I. Consistently, addition of (NH4)2SO4 to cells of the E. coli mutant containing cytochrome bd-I as the only terminal oxidase at pH 8.3 accelerates the O2 consumption rate, the highest one (140%) being at 27 mM (NH4)2SO4. We discuss possible molecular mechanisms and physiological significance of modulation of the enzymatic activities by ammonia present at high concentration in the intestines, a niche occupied by E. coli.

scholarly journals SlyA and H-NS Regulate Transcription of the Escherichia coli K5 Capsule Gene Cluster, and Expression of slyA in Escherichia coli Is Temperature-dependent, Positively Autoregulated, and Independent of H-NS

2007 ◽  
Vol 282 (46) ◽  
pp. 33326-33335 ◽  
Author(s):  
David Corbett ◽  
Hayley J. Bennett ◽  
Hamdia Askar ◽  
Jeffrey Green ◽  
Ian S. Roberts
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Regulation Of Transcription ◽  
Temperature Dependent ◽  
Mobility Shift ◽  
E Coli ◽  
Dnase I Footprinting ◽  
Nucleoprotein Complex ◽  
Electrophoretic Mobility Shift Assays

In this paper, we present the first evidence of a role for the transcriptional regulator SlyA in the regulation of transcription of the Escherichia coli K5 capsule gene cluster and demonstrate, using a combination of reporter gene fusions, DNase I footprinting, and electrophoretic mobility shift assays, the dependence of transcription on the functional interplay between H-NS and SlyA. Both SlyA and H-NS bind to multiple overlapping sites within the promoter in vitro, but their binding is not mutually exclusive, resulting in a remodeled nucleoprotein complex. In addition, we show that expression of the E. coli slyA gene is temperature-regulated, positively autoregulated, and independent of H-NS.

Hygienic Effects of Trimming and Washing Operations in a Beef-Carcass-Dressing Process†

1996 ◽  
Vol 59 (6) ◽  
pp. 666-669 ◽  
Author(s):  
C. O. GILL ◽  
M. BADONI ◽  
T. JONES
Keyword(s):  
Escherichia Coli ◽  
Standard Deviation ◽  
High Speed ◽  
Effective Means ◽  
Arithmetic Mean ◽  
Single Sample ◽  
Aerobic Bacteria ◽  
E Coli ◽  
Beef Carcasses ◽  
The Mean

Swab samples were obtained from the surfaces of randomly selected beef carcasses passing through a high-speed dressing process. A single sample was obtained from a randomly selected site on the surface of each selected carcass. Fifty such samples were collected at each of four stages in the process. The aerobic bacteria, coliforms, and Escherichia coli recovered from each sample were enumerated. Values for the mean log units and standard deviations of each set of 50 log values were calculated on the assumption that the log values were normally distributed. The log of the arithmetic mean was estimated from the mean log and standard deviation values for each set. The results show that the average numbers of E. coli, coliforms, and aerobic bacteria which are deposited on carcasses during skinning and evisceration are not reduced by trimming, and that washing approximately halves the average numbers of those bacteria on carcasses. It is concluded that commercial trimming and washing operations are not effective means of decontaminating beef carcasses.

scholarly journals A study of SeqA subcellular localization in Escherichia coli using photo-activated localization microscopy

2015 ◽  
Vol 184 ◽  
pp. 425-450 ◽  
Author(s):  
Jacek T. Mika ◽  
Aster Vanhecke ◽  
Peter Dedecker ◽  
Toon Swings ◽  
Jeroen Vangindertael ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Cycle ◽  
Bacterial Genome ◽  
Genetically Engineered ◽  
Replication Initiation ◽  
Cell Protein ◽  
Experimental Conditions ◽  
Localization Microscopy ◽  
E Coli ◽  
Copy Numbers

Escherichia coli (E. coli) cells replicate their genome once per cell cycle to pass on genetic information to the daughter cells. The SeqA protein binds the origin of replication, oriC, after DNA replication initiation and sequesters it from new initiations in order to prevent overinitiation. Conventional fluorescence microscopy studies of SeqA localization in bacterial cells have shown that the protein is localized to discrete foci. In this study we have used photo-activated localization microscopy (PALM) to determine the localization of SeqA molecules, tagged with fluorescent proteins, with a localization precision of 20–30 nm with the aim to visualize the SeqA subcellular structures in more detail than previously possible. SeqA–PAmCherry was imaged in wild type E. coli, expressed from plasmid or genetically engineered into the bacterial genome, replacing the native seqA gene. Unsynchronized cells as well as cells with a synchronized cell cycle were imaged at various time points, in order to investigate the evolution of SeqA localization during the cell cycle. We found that SeqA indeed localized into discrete foci but these were not the only subcellular localizations of the protein. A significant amount of SeqA–PAmCherry molecules was localized outside the foci and in a fraction of cells we saw patterns indicating localization at the membrane. Using quantitative PALM, we counted protein copy numbers per cell, protein copy numbers per focus, the numbers of foci per cell and the sizes of the SeqA clusters. The data showed broad cell-to-cell variation and we did not observe a correlation between SeqA–PAmCherry protein numbers and the cell cycle under the experimental conditions of this study. The numbers of SeqA–PAmCherry molecules per focus as well as the foci sizes also showed broad distributions indicating that the foci are likely not characterized by a fixed number of molecules. We also imaged an E. coli strain devoid of the dam methylase (Δdam) and observed that SeqA–PAmCherry no longer formed foci, and was dispersed throughout the cell and localized to the plasma membrane more readily. We discuss our results in the context of the limitations of the technique.

scholarly journals Stationary-Phase Regulation of RpoS Translation in Escherichia coli

2005 ◽  
Vol 187 (21) ◽  
pp. 7204-7213 ◽  
Author(s):  
Matthew Hirsch ◽  
Thomas Elliott
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Osmotic Shock ◽  
Transcriptional Response ◽  
Enteric Bacteria ◽  
Protein Activity ◽  
E Coli ◽  
Phase Regulation ◽  
Shine Dalgarno Sequence ◽  
Necessary And Sufficient

ABSTRACT In enteric bacteria, adaptation to a number of different stresses is mediated by the RpoS protein, one of several sigma factors that collectively allow a tailored transcriptional response to environmental cues. Stress stimuli including low temperature, osmotic shock, nutrient limitation, and growth to stationary phase (SP) all result in a substantial increase in RpoS abundance and activity. The mechanism of regulation depends on the specific signal but may occur at the level of transcription, translation, protein activity, or targeted proteolysis. In both Escherichia coli and Salmonella enterica, SP induction of RpoS in rich medium is >30 fold and includes effects on both transcription and translation. Recently, we found that SP control of rpoS transcription in S. enterica involves repression of the major rpoS promoter during exponential phase by the global transcription factor Fis. Working primarily with E. coli, we now show that 24 nucleotides of the rpoS ribosome-binding site (RBS) are necessary and sufficient for a large part of the increase in rpoS translation as cells grow to SP. Genetic evidence points to an essential role for the leader nucleotides just upstream of the Shine-Dalgarno sequence but is conflicted on the question of whether sequence or structure is important. SP regulation of rpoS is conserved between E. coli and S. enterica. When combined with an fis mutation to block transcriptional effects, replacement of the rpoS RBS sequence by the lacZ RBS eliminates nearly all SP induction of RpoS.

scholarly journals Temperature Dependence of MinD Oscillation in Escherichia coli: Running Hot and Fast

2006 ◽  
Vol 188 (21) ◽  
pp. 7661-7667 ◽  
Author(s):  
Ahmed Touhami ◽  
Manfred Jericho ◽  
Andrew D. Rutenberg
Keyword(s):  
Escherichia Coli ◽  
Temperature Dependence ◽  
Growth Curve ◽  
Oscillation Period ◽  
Quantitative Model ◽  
Temperature Dependent ◽  
E Coli ◽  
Temperature Range ◽  
Characteristic Wavelength ◽  
Dependent Growth

ABSTRACT We observed that the oscillation period of MinD within rod-like and filamentous cells of Escherichia coli varied by a factor of 4 in the temperature range from 20°C to 40°C. The detailed dependence was Arrhenius, with a slope similar to the overall temperature-dependent growth curve of E. coli. The detailed pattern of oscillation, including the characteristic wavelength in filamentous cells, remained independent of temperature. A quantitative model of MinDE oscillation exhibited similar behavior, with an activated temperature dependence of the MinE-stimulated MinD-ATPase rate.

scholarly journals Ethanol production by Escherichia coli from detoxified lignocellulosic teak wood hydrolysates with high concentration of phenolic compounds

2021 ◽  
Author(s):  
Estefanía Sierra-Ibarra ◽  
Jorge Alcaraz-Cienfuegos ◽  
Alejandra Vargas-Tah ◽  
Alberto Rosas-Aburto ◽  
Ángeles Valdivia-López ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Phenolic Compounds ◽  
Ethanol Production ◽  
Enzymatic Saccharification ◽  
Coli Strain ◽  
High Concentration ◽  
E Coli ◽  
Thermochemical Pretreatment ◽  
Teak Wood ◽  
Ethanologenic Escherichia Coli

Abstract Teak wood residues were subjected to thermochemical pretreatment, enzymatic saccharification, and detoxification to obtain syrups with a high concentration of fermentable sugars for ethanol production with the ethanologenic Escherichia coli strain MS04. Teak is a hardwood, and thus a robust deconstructive pretreatment was applied followed by enzymatic saccharification. The resulting syrup contained 60 g L−1 glucose, 18 g L−1 xylose, 6 g L−1 acetate, less than 0.1 g L−1 of total furans, and 12 g L−1 of soluble phenolic compounds (SPC). This concentration of SPC is toxic to E. coli, and thus two detoxification strategies were assayed: 1) treatment with Coriolopsis gallica laccase followed by addition of activated carbon and 2) overliming with Ca(OH)2. These reduced the phenolic compounds by 40 and 76%, respectively. The detoxified syrups were centrifuged and fermented with E. coli MS04. Cultivation with the over-limed hydrolysate showed a 60% higher volumetric productivity (0.45 gETOH L−1 h−1). The bioethanol/sugars yield was over 90% in both strategies.

scholarly journals Balanced Input from the tRNA Prenyltransferase MiaA Controls the Stress Resistance and Virulence Potential of Extraintestinal Pathogenic Escherichia coli

2021 ◽  
Author(s):  
Matthew G. Blango ◽  
Brittany A. Fleming ◽  
William M. Kincannon ◽  
Alex Tran ◽  
Adam J. Lewis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Stress Resistance ◽  
Osmotic Shock ◽  
Bloodstream Infections ◽  
E Coli ◽  
Translational Frameshifting ◽  
Virulence Potential ◽  
Pathogenic Escherichia Coli ◽  
Hostile Environments ◽  
Fine Tune

ABSTRACTAn ability to adapt to rapidly changing and often hostile environments is key to the success of many bacterial pathogens. In Escherichia coli, the highly conserved enzymes MiaA and MiaB mediate the sequential prenylation and methylthiolation of adenosine-37 within tRNAs that decode UNN codons. Here, we show that MiaA, but not MiaB, is critical to the fitness and virulence of extraintestinal pathogenic E. coli (ExPEC), a major cause of urinary tract and bloodstream infections. Deletion of miaA has pleiotropic effects, rendering ExPEC especially sensitive to stressors like nitrogen and oxygen radicals and osmotic shock. We find that stress can stimulate striking changes in miaA expression, which in turn can increase translational frameshifting and markedly alter the bacterial proteome. Cumulatively, these data indicate that ExPEC, and likely other organisms, can vary MiaA levels as a means to fine-tune translation and the spectrum of expressed proteins in response to changing environmental challenges.

Inhibition of Growth of Escherichia coli O157:H7 in Fresh Radish (Raphanus sativus L.) Sprout Production by Calcinated Calcium

1999 ◽  
Vol 62 (2) ◽  
pp. 128-132 ◽  
Author(s):  
M. L. BARI ◽  
H. KUSUNOKI ◽  
H. FURUKAWA ◽  
H. IKEDA ◽  
K. ISSHIKI ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Raphanus Sativus ◽  
Inhibitory Effect ◽  
Seed Extract ◽  
Escherichia Coli O157 ◽  
Experimental Conditions ◽  
E Coli ◽  
Inhibition Of Growth ◽  
Raphanus Sativus L ◽  
Radish Sprouts

The inhibitory effect of calcinated calcium on the growth of Escherichia coli O157:H7 during fresh radish (Raphanus sativus L.) sprout production was studied. It was revealed that the addition of 0.4% (wt/vol) calcinated calcium into radish sprouting medium which was artificially contaminated with E. coli O157:H7 (3.0 to 3.2 log CFU/ml) completely inhibited the growth or inactivated the microorganism. When radish seed extract was used instead of radish sprout production, the same extent of growth inhibition or inactivation was observed with much lower amounts (0.07%) of calcinated calcium under similar experimental conditions. The findings suggested that calcinated calcium may be useful to control E. coli O157:H7 contamination during the production of radish sprouts.

scholarly journals Binding of Escherichia coli heat-stable enterotoxin to receptors on rat intestinal cells

1983 ◽  
Vol 245 (4) ◽  
pp. G492-G498 ◽  
Author(s):  
R. A. Giannella ◽  
M. Luttrell ◽  
M. Thompson
Keyword(s):  
Escherichia Coli ◽  
Binding Sites ◽  
Intestinal Epithelial Cells ◽  
Cell Number ◽  
Intestinal Cells ◽  
Negative Cooperativity ◽  
Intestinal Epithelial ◽  
Temperature Dependent ◽  
E Coli ◽  
Heat Stable

This study was performed to determine whether receptors for Escherichia coli heat-stable enterotoxin (ST) exist on intestinal epithelial cells. Binding sites for 125I-ST were found on rat jejunal and ileal villus cells. Binding was rapid, reversible, linear with cell number, saturable, and temperature dependent. Significant degradation of 125I-ST occurred when incubated with cells at 37 degrees C but not at 25 degrees C. Binding was specific to ST since binding of 125I-ST was competitively inhibited by increasing concentrations of human or porcine ST but not by E. coli heat-labile, cholera, or staphylococcal enterotoxins. Addition of excess unlabeled ST to cells preincubated with 125I-ST resulted in dissociation of much but not all of the bound 125I-ST. Binding of 125I-ST to jejunal and ileal cells occurs with two affinities, and this is due to the phenomenon of negative cooperativity. The potency of ST for inhibiting the binding of 125I-ST was identical to the potency of ST in stimulating cGMP production. These data support the existence of receptors for ST on intestinal cells, and these receptors may be involved in the action of ST.

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