scholarly journals The dynamic balance of import and export of zinc in Escherichia coli suggests a heterogeneous population response to stress

2015 ◽  
Vol 12 (106) ◽  
pp. 20150069 ◽  
Author(s):  
Hiroki Takahashi ◽  
Taku Oshima ◽  
Jon L. Hobman ◽  
Neil Doherty ◽  
Selina R. Clayton ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Zinc Concentration ◽  
Systems Approach ◽  
Model Simulation ◽  
Dynamic Balance ◽  
Model Fitting ◽  
Viable Cell ◽  
Population Heterogeneity ◽  
Cell Counts ◽  
Import And Export

Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli . We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments.

Performance of Some Heat-Sensitive Differential Agars Prepared and Melted by Microwave Energy1

1988 ◽  
Vol 51 (7) ◽  
pp. 577-578 ◽  
Author(s):  
C. LIANG ◽  
D. Y. C. FUNG
Keyword(s):  
Escherichia Coli ◽  
Cell Count ◽  
Viable Cell ◽  
Microwave Energy ◽  
Microwave Oven ◽  
Viable Cell Count ◽  
Streptococcus Faecalis ◽  
Cell Counts ◽  
Significant Difference ◽  
Conventional Boiling

The viable cell count performance of some heat-sensitive differential agars prepared and remelted by microwave energy was evaluated for Salmonella choleraesui, Streptococcus faecalis and Escherichia coli. The conventional boiling method was used for comparison. No significant difference was found between the microwave oven processed agar and the conventional-boiling processed agar in viable cell counts of the target bacteria. Heating and reheating of violet red bile agar, bismuth sulfite agar, and KF Streptococcus agar by both methods did not change agar performance. However, remelting of desoxycholate citrate agar by both methods resulted in a substantial lowering of viable cell counts.

Isolation and Purification of Colicin ECL 12, a Bacteriocin That Inhibits Strains of Escherichia coli O157:H7†

1997 ◽  
Vol 60 (12) ◽  
pp. 1520-1528 ◽  
Author(s):  
WANDA J. LYON ◽  
DENNIS G. OLSON
Keyword(s):  
Escherichia Coli ◽  
Proteolytic Enzymes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Viable Cell ◽  
Exchange Chromatography ◽  
Isolation And Purification ◽  
E Coli ◽  
Log Reduction ◽  
Cell Counts

A swine fecal isolate, identified as Escherichia coli ECL12, was found to produce an antimicrobial substance designated as colicin ECL12. Colicin ECL12 was inhibitory against 20 strains of E. coli O157:H7 previously isolated from both human and bovine feces. Identification of the producer strain was determined phenotypically by biochemical and morphological tests. Colicin ECL12 was sensitive to several proteolytic enzymes. Adsorption of colicin ECL12 to sensitive cells of E. coli O157:H7 was bactericidal, resulting in a 2 log reduction in viable cell counts. Colicin ECL12 was purified from strain ECL12 by cell extraction and ion-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of colicin ECL12 resolved a single protein with a molecular weight of approximately 65,000.

scholarly journals Validation of a Noninvasive, Real-Time Imaging Technology Using Bioluminescent Escherichia coli in the Neutropenic Mouse Thigh Model of Infection

2001 ◽  
Vol 45 (1) ◽  
pp. 129-137 ◽  
Author(s):  
H. L. Rocchetta ◽  
C. J. Boylan ◽  
J. W. Foley ◽  
P. W. Iversen ◽  
D. L. LeTourneau ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Real Time ◽  
Antimicrobial Agents ◽  
Viable Cell ◽  
Multicopy Plasmid ◽  
In Vivo Evaluation ◽  
Therapeutic Success ◽  
Cell Counts

ABSTRACT A noninvasive, real-time detection technology was validated for qualitative and quantitative antimicrobial treatment applications. Thelux gene cluster of Photorhabdus luminescenswas introduced into an Escherichia coli clinical isolate, EC14, on a multicopy plasmid. This bioluminescent reporter bacterium was used to study antimicrobial effects in vitro and in vivo, using the neutropenic-mouse thigh model of infection. Bioluminescence was monitored and measured in vitro and in vivo with an intensified charge-coupled device (ICCD) camera system, and these results were compared to viable-cell determinations made using conventional plate counting methods. Statistical analysis demonstrated that in the presence or absence of antimicrobial agents (ceftazidime, tetracycline, or ciprofloxacin), a strong correlation existed between bioluminescence levels and viable cell counts in vitro and in vivo. Evaluation of antimicrobial agents in vivo could be reliably performed with either method, as each was a sound indicator of therapeutic success. Dose-dependent responses could also be detected in the neutropenic-mouse thigh model by using either bioluminescence or viable-cell counts as a marker. In addition, the ICCD technology was examined for the benefits of repeatedly monitoring the same animal during treatment studies. The ability to repeatedly measure the same animals reduced variability within the treatment experiments and allowed equal or greater confidence in determining treatment efficacy. This technology could reduce the number of animals used during such studies and has applications for the evaluation of test compounds during drug discovery.

Antimicrobial Performance of Alkaline Ionic Fluid (GC-100X) and Its Ability To Remove Escherichia coli O157:H7 from the Surface of Tomatoes

2003 ◽  
Vol 66 (9) ◽  
pp. 1604-1610 ◽  
Author(s):  
N. H. KWON ◽  
S. H. KIM ◽  
J. Y. KIM ◽  
J. Y. LIM ◽  
J. M. KIM ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Hard Water ◽  
Viable Cell ◽  
Organic Load ◽  
Korean Isolate ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Cell Counts ◽  
Chlorine Water

An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens—Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637—at three different temperatures (4, 25, and 36°C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 × 104 CFU/ml reduction) against all pathogens reacted at 37°C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.

Application of bacteriophages EP75 and EP335 efficiently reduces viable cell counts of Escherichia coli O157 on beef and vegetables

2022 ◽  
pp. 103978
Author(s):  
Sander Witte ◽  
Linda Huijboom ◽  
Silvia Klamert ◽  
Leoni van de Straat ◽  
Steven Hagens ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Viable Cell ◽  
Escherichia Coli O157 ◽  
Cell Counts

scholarly journals Persister cells mediate tolerance to metal oxyanions in Escherichia coli

Microbiology ◽  
2005 ◽  
Vol 151 (10) ◽  
pp. 3181-3195 ◽  
Author(s):  
Joe J. Harrison ◽  
Howard Ceri ◽  
Nicole J. Roper ◽  
Erin A. Badry ◽  
Kimberley M. Sproule ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Viable Cell ◽  
Small Population ◽  
Water Soluble ◽  
Bacterial Cells ◽  
Persister Cells ◽  
Term Survival ◽  
E Coli ◽  
Cell Counts ◽  
High Concentrations

Bacterial cultures produce subpopulations of cells termed ‘persisters’, reputedly known for high tolerance to killing by antibiotics. Ecologically, antibiotics produced by competing microflora are only one potential stress encountered by bacteria. Another pressure in the environment is toxic metals that are distributed ubiquitously by human pollution, volcanic activity and the weathering of minerals. This study evaluated the time- and concentration-dependent killing of Escherichia coli planktonic and biofilm cultures by the water-soluble metal(loid) oxyanions chromate (), arsenate (), arsenite (), selenite (), tellurate () and tellurite (). Correlative to previous reports in the literature, control antibiotic assays indicated that a small proportion of E. coli biofilm populations remained recalcitrant to killing by antibiotics (even with 24 h exposure). In contrast, metal oxyanions presented a slow, bactericidal action that eradicated biofilms. When exposed for 2 h, biofilms were up to 310 times more tolerant to killing by metal oxyanions than corresponding planktonic cultures. However, by 24 h, planktonic cells and biofilms were eradicated at approximately the same concentration in all instances. Coloured complexes of metals and chelators could not be generated in biofilms exposed to or , suggesting that the extracellular polymeric matrix of E. coli may have a low binding affinity for metal oxyanions. Viable cell counts at 2 and 24 h exposure revealed that, at high concentrations, all of the metal oxyanions had killed 99 % (or a greater proportion) of the bacterial cells in biofilm populations. It is suggested here that the short-term survival of <1 % of the bacterial population corresponds well with the hypothesis that a small population of persister cells may be responsible for the time-dependent tolerance of E. coli biofilms to high concentrations of metal oxyanions.

Combined Effect of Water Activity and pH on the Inhibition of Escherichia coli by Nisin

2001 ◽  
Vol 64 (10) ◽  
pp. 1510-1514 ◽  
Author(s):  
PATRICIA CERRUTTI ◽  
MAURICIO R. TEREBIZNIK ◽  
MARTA SEGOVIA de HUERGO ◽  
ROSA JAGUS ◽  
ANA M. R. PILOSOF
Keyword(s):  
Escherichia Coli ◽  
Water Activity ◽  
Viable Cell ◽  
Stress Factors ◽  
Doehlert Design ◽  
Survival Fraction ◽  
E Coli ◽  
Cell Counts ◽  
Maximum Inhibition ◽  
Influence Of Ph

The Doehlert design and surface response methodology were used to study the influence of pH and water activity (aw) on Escherichia coli inhibition by nisin. Combining stress factors at levels where they are not inhibitory by themselves, a reduction of E. coli survival fraction can be achieved with lower nisin doses than in a single nisin treatment. For all the pH values assayed, a synergistic effect of aw and nisin concentration was detected, and the isoresponse lines showed the existence of an area of maximum inhibition. Factors that reduced viable cell counts by 4 to 5 log cycles were 1,000 to 1,400 IU of nisin per ml at pH 5.5 to 6.5 and a water activity of 0.97 and 0.98. The addition of different ionic and nonionic solutes to control aw suggested that the effect of aw in the inhibitory action of nisin on E. coli cells was not solute-specific. The use of the Doehlert experimental design was effective to determine the optimal combination of stress factors, as well as to point out the most important variables that affected E. coli inhibition.

scholarly journals Biofilm formation by South African non-O157 Shiga toxigenic Escherichia coli on stainless steel coupons

2020 ◽  
Vol 66 (4) ◽  
pp. 328-336 ◽  
Author(s):  
Emmanuel W. Bumunang ◽  
Collins N. Ateba ◽  
Kim Stanford ◽  
Tim A. McAllister ◽  
Yan D. Niu
Keyword(s):  
Escherichia Coli ◽  
Stainless Steel ◽  
South African ◽  
Food Processing ◽  
Biofilm Formation ◽  
Viable Cell ◽  
Liquid Interface ◽  
Cell Counts ◽  
Potential Source ◽  
Air Liquid Interface

This study examined the biofilm-forming ability of six non-O157 Shiga-toxin-producing Escherichia coli (STEC) strains: O116:H21, wzx-Onovel5:H19, O129:H21, O129:H23, O26:H11, and O154:H10 on stainless steel coupons after 24, 48, and 72 h of incubation at 22 °C and after 168 h at 10 °C. The results of crystal violet staining revealed that strains O129:H23 and O154:H10 were able to form biofilms on both the submerged surface and the air–liquid interface of coupons, whereas strains O116:H21, wzx-Onovel5:H19, O129:H21, and O26:H11 formed biofilm only at the air–liquid interface. Viable cell counts and scanning electron microscopy showed that biofilm formation increased (p < 0.05) over time. The biofilm-forming ability of non-O157 STEC was strongest (p < 0.05) at 22 °C after 48 h of incubation. The strongest biofilm former regardless of temperature was O129:H23. Generally, at 10 °C, weak to no biofilm was observed for isolates O154:H10, O116:H21, wzx-Onovel5:H19, O26:H11, and O129:H21 after 168 h. This study found that temperature affected the biofilm-forming ability of non-O157 STEC strains. Overall, our data indicate a high potential for biofilm formation by the isolates at 22 °C, suggesting that non-O157 STEC strains could colonize stainless steel within food-processing facilities. This could serve as a potential source of adulteration and promote the dissemination of these potential pathogens in food.

Inhibition of the induced synthesis of protocatechuate oxygenase by o-nitrobenzoic acid

1970 ◽  
Vol 16 (7) ◽  
pp. 609-614
Author(s):  
Karen F. Montgomery ◽  
Norman N. Durham
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Trichloroacetic Acid ◽  
Protocatechuic Acid ◽  
Viable Cell ◽  
Insoluble Fraction ◽  
Nitrobenzoic Acid ◽  
Cell Counts ◽  
Oxygenase Activity

The synthesis of protocatechuate oxygenase (EC. 1.13.1.3), an inducible enzyme, by Pseudomonas fluorescens was inhibited by o-nitrobenzoic acid. The inhibitor did not alter the oxygenase activity of induced cells. Viable cell counts indicated that o-nitrobenzoic acid, in the concentrations used in these experiments, did not kill the cells. The inhibitor decreased the incorporation of L-tryptophan-14C and DL-glutamic-14C acid into the hot trichloroacetic acid insoluble fraction of the cell, but had no effect on the uptake of either radioactive amino acids or the inducer, protocatechuic acid. The synthesis of β-galactosidase by Escherichia coli was also inhibited by o-nitrobenzoic acid. The results establish that one site of o-nitrobenzoic acid inhibition is associated with protein synthesis in the cell.

Minimum and Maximum Temperatures for Growth and Verotoxin Production by Hemorrhagic Strains of Escherichia coli

1995 ◽  
Vol 58 (4) ◽  
pp. 352-356 ◽  
Author(s):  
SAMUEL A. PALUMBO ◽  
JEFFREY E. CALL ◽  
FRANKIE J. SCHULTZ ◽  
AARON C. WILLIAMS
Keyword(s):  
Escherichia Coli ◽  
Brain Heart Infusion ◽  
Viable Cell ◽  
Toxin Production ◽  
Viable Count ◽  
Influence Of Temperature ◽  
E Coli ◽  
Cell Counts ◽  
Influence Of Temperature On ◽  
Maximum Temperatures

The influence of temperature on growth and verotoxin production by Escherichia coli strains was studied in brain heart infusion (BHI) broth both in shake cultures at various temperatures and in a temperature-gradient incubator. All strains of E. coli surveyed grew from at least 10 to 45°C, with some strains growing at 8° C. Verotoxin production (determined using the Vero cell–assay system) was a function of both temperature and time, with the highest titers produced at temperatures supporting the fastest growth (based on days to visible turbidity) and highest viable cell counts. However, for strains producing verotoxin, toxin production was detected at any temperature supporting growth. Three strains (of 16 tested) increased 1000-fold in viable count in 4 to 6 days at 10°C. The data presented here indicate that most E. coli strains surveyed can easily grow at ca. 10°C and thus suggest the potential for growth in temperature-abused refrigerated foods.

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