scholarly journals The relationship between intracellular pH, the pH gradient and potassium transport in Escherichia coli

1983 ◽  
Vol 216 (3) ◽  
pp. 709-716 ◽  
Author(s):  
R G Kroll ◽  
I R Booth
Keyword(s):  
Escherichia Coli ◽  
Intracellular Ph ◽  
Feedback Regulation ◽  
Potassium Transport ◽  
Potassium Uptake ◽  
Ph Gradient ◽  
Limited Capacity ◽  
E Coli ◽  
The Relationship ◽  
K Transport

The capacity of E. coli cells to regulate intracellular pH (pHi) during net potassium uptake has been investigated. The data show: (a) that cells sense their intracellular pH; (b) that the pH gradient (delta pH) exerts a feedback regulation on pHi; (c) that a mechanism of regulation of pHi exists which may be independent of Na+ [Zilberstein, Agmon, Schuldiner & Padan (1982) J. Biol. Chem. 257, 3687-3691]; and (d) that cells have a limited capacity to raise their intracellular pH in the absence of net K+ transport.

scholarly journals The role of potassium transport in the generation of a pH gradient in Escherichia coli

1981 ◽  
Vol 198 (3) ◽  
pp. 691-698 ◽  
Author(s):  
R G Kroll ◽  
I R Booth
Keyword(s):  
Escherichia Coli ◽  
Membrane Potential ◽  
Respiratory Rate ◽  
Potassium Transport ◽  
Ph Gradient ◽  
Simple Relationship ◽  
K Uptake ◽  
Net Uptake ◽  
K Transport

The role of K+ transport in the generation of a pH gradient in Escherichia coli has been investigated. In K+-depleted cells, net K+ uptake dissipated delta psi (membrane potential) and led to an increase in delta pH (pH gradient). The magnitude of the delta pH formed bore a simple relationship to the net K+ uptake and was substantially independent of the respiratory rate. In K+-replete cells, generation of a pH gradient was again K+-dependent, although no net uptake of this cation occurred. The results are discussed in terms of K+ cycling, and it is suggested that delta pH is in part a function of the rate of cycling and independent of the respiratory rate.

Contribution of SOS Genes to H2O2-induced Apoptosis-like Death in Escherichia Coli

2021 ◽  
Author(s):  
Heesu Kim ◽  
Dong Gun Lee
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Treatment Strategies ◽  
Sos Response ◽  
Bacterial Dna ◽  
E Coli ◽  
New Treatment ◽  
Induced Apoptosis ◽  
And Function ◽  
The Relationship

Abstract Hydrogen peroxide (H2O2) is a debriding agent that damages the microbial structure and function by generating various reactive oxygen species (ROS). H2O2-produced hydroxyl radical (OH∙) also exert oxidative stress on microorganisms. The spread of antibiotic resistance in bacteria is a serious issue worldwide, and greater efforts are needed to identify and characterize novel antibacterial mechanisms to develop new treatment strategies. Therefore, this study aimed to clarify the relationship between H2O2 and Escherichia coli and to elucidate a novel antibacterial mechanism(s) of H2O2. Following H2O2 exposure, increased levels of 8-hydroxyldeoxyguanosine and malondialdehyde indicated that H2O2 accelerates oxidation of bacterial DNA and lipids in E. coli. As oxidative damage worsened, the SOS response was triggered. Cell division arrest and resulting filamentation were identified in cells, indicating that LexA was involved in DNA replication. It was also verified that RecA, a representative SOS gene, helps self-cleavage of LexA and acts as a bacterial caspase-like protein. Our findings also showed that dinF is essential to preserve E. coli from H2O2-induced ROS, and furthermore, demonstrated that H2O2-induced SOS response and SOS genes participate differently in guarding E. coli from oxidative stress. As an extreme SOS response is considered apoptosis-like death (ALD) in bacteria, additional experiments were performed to examine the characteristics of ALD. DNA fragmentation and membrane depolarization appeared in H2O2-treated cells, suggesting that H2O2 causes ALD in E. coli. In conclusion, our investigations revealed that ALD is a novel antibacterial mode of action(s) of H2O2 with important contributions from SOS genes.

Survival of Escherichia coli on Lettuce under Field Conditions Encountered in the Northeastern United States

2017 ◽  
Vol 80 (7) ◽  
pp. 1214-1221 ◽  
Author(s):  
Daniel L. Weller ◽  
Jasna Kovac ◽  
Sherry Roof ◽  
David J. Kent ◽  
Jeffrey I. Tokman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Microbial Contamination ◽  
Field Conditions ◽  
Risk Assessments ◽  
Most Probable Number ◽  
Northeastern United States ◽  
Probable Number ◽  
E Coli ◽  
The Relationship ◽  
Sample Time

ABSTRACT Although wildlife intrusion and untreated manure have been associated with microbial contamination of produce, relatively few studies have examined the survival of Escherichia coli on produce under field conditions following contamination (e.g., via splash from wildlife feces). This experimental study was performed to estimate the die-off rate of E. coli on preharvest lettuce following contamination with a fecal slurry. During August 2015, field-grown lettuce was inoculated via pipette with a fecal slurry that was spiked with a three-strain cocktail of rifampin-resistant nonpathogenic E. coli. Ten lettuce heads were harvested at each of 13 time points following inoculation (0, 2.5, 5, and 24 h after inoculation and every 24 h thereafter until day 10). The most probable number (MPN) of E. coli on each lettuce head was determined, and die-off rates were estimated. The relationship between sample time and the log MPN of E. coli per head was modeled using a segmented linear model. This model had a breakpoint at 106 h (95% confidence interval = 69, 142 h) after inoculation, with a daily decrease of 0.70 and 0.19 log MPN for 0 to 106 h and 106 to 240 h following inoculation, respectively. These findings are consistent with die-off rates obtained in similar studies that assessed E. coli survival on produce following irrigation. Overall, these findings provide die-off rates for E. coli on lettuce that can be used in future quantitative risk assessments.

Distribution of Coliphages in Various Foods

1986 ◽  
Vol 49 (12) ◽  
pp. 944-951 ◽  
Author(s):  
J. E. KENNEDY ◽  
C. I. WEI ◽  
J. L. OBLINGER
Keyword(s):  
Escherichia Coli ◽  
Food Samples ◽  
Fecal Coliforms ◽  
Bacterial Indicators ◽  
Processed Meats ◽  
E Coli ◽  
Plate Counts ◽  
The Relationship

The distribution of coliphages in various foods and the relationship between the incidences of coliphages and bacterial indicators were investigated. A total of 120 food samples comprising twelve products and including fresh meats, shellfish, vegetables and processed meats, were analyzed for indigenous coliphages using Escherichia coli hosts C, C-3000 and B. Bacterial analyses included enumeration of E. coli, fecal coliforms and coliforms, as well as aerobic plate counts and Salmonella analyses. Coliphages were detected (≥10 PFU/100 g) in 56% of samples and eleven of twelve products. Coliphages, E. coli, fecal coliforms and coliforms were recovered at a level of at least 30 organisms per 100 g in 43, 43, 68 and 81% of samples, with overall mean recoveries of 13, 19, 93 and 4300 organisms/100 g, respectively. Highest and lowest recoveries of coliphages and E. coli were from fresh meats and vacuum-packaged processed meats, respectively. Significant nonparametric correlations between coliphages, E. coli, fecal coliforms and coliforms were found among all food samples.

Mechanism of Action of Spanish Oregano, Chinese Cinnamon, and Savory Essential Oils against Cell Membranes and Walls of Escherichia coli O157:H7 and Listeria monocytogenes

2006 ◽  
Vol 69 (5) ◽  
pp. 1046-1055 ◽  
Author(s):  
MOUNIA OUSSALAH ◽  
STÉPHANE CAILLET ◽  
MONIQUE LACROIX
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Essential Oils ◽  
Intracellular Ph ◽  
Cell Membranes ◽  
Escherichia Coli O157 ◽  
Electronic Microscopy ◽  
Cinnamon Oil ◽  
E Coli ◽  
Atp Concentration

The mechanism of the antimicrobial action of Spanish oregano (Corydothymus capitatus), Chinese cinnamon (Cinnamomum cassia), and savory (Satureja montana) essential oils against cell membranes and walls of bacteria was studied by the measurement of the intracellular pH and ATP concentration, the release of cell constituents, and the electronic microscopy observations of the cells when these essential oils at their MICs were in contact with Escherichia coli O157:H7 and Listeria monocytogenes. E. coli O157:H7 and L. monocytogenes, two pathogenic foodborne bacteria, were used as gram-negative and gram-positive bacterial models, respectively. Treatment with these essential oils at their MICs affected the membrane integrity of bacteria and induced depletion of the intracellular ATP concentration. Spanish oregano and savory essential oils, however, induced more depletion than Chinese cinnamon oil. An increase of the extracellular ATP concentration was observed only when Spanish oregano and savory oils were in contact with E. coli O157:H7 and L. monocytogenes. Also, a significantly higher (P ≤0.05) cell constituent release was observed in the supernatant when E. coli O157:H7 and L. monocytogenes cells were treated with Chinese cinnamon and Spanish oregano oils. Chinese cinnamon oil was more effective to reduce significantly the intracellular pH of E. coli O157:H7, whereas Chinese cinnamon and Spanish oregano decreased more significantly the intracellular pH of L. monocytogenes. Electronic microscopy observations revealed that the cell membrane of both treated bacteria was significantly damaged. These results suggest that the cytoplasmic membrane is involved in the toxic action of essential oils.

scholarly journals Characterization of the β-lactamase specified by the resistance factor R-1818 in Escherichia coli K12 and other Gram-negative bacteria

1971 ◽  
Vol 123 (4) ◽  
pp. 501-505 ◽  
Author(s):  
J. W. Dale
Keyword(s):  
Escherichia Coli ◽  
Host Species ◽  
Host Bacterium ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli ◽  
R Factor ◽  
Relationship Of ◽  
The Relationship

1. The amino acid composition of the β-lactamase from E. coli (R-1818) was determined. 2. The R-1818 β-lactamase is inhibited by formaldehyde, hydroxylamine, sodium azide, iodoacetamide, iodine and sodium chloride. 3. The Km values for benzylpenicillin, ampicillin and oxacillin have been determined by using the R-factor enzyme from different host species. The same values were obtained, irrespective of the host bacterium. 4. The molecular weight of the enzyme was found to be 44600, and was the same for all host species. 5. The relationship of R-1818 and R-GN238 β-lactamases is discussed.

scholarly journals Can Pathogenic and Nonpathogenic Bacteria Be Distinguished by Sensory Protein Abundance?

2020 ◽  
Vol 86 (14) ◽  
Author(s):  
Subhrajit Bhar ◽  
Tungadri Bose ◽  
Sharmila S. Mande
Keyword(s):  
Escherichia Coli ◽  
Genome Size ◽  
Ecological Niche ◽  
Environmental Changes ◽  
Ecological Niches ◽  
Content Type ◽  
E Coli ◽  
Depth Analysis ◽  
Component Systems ◽  
The Relationship

ABSTRACT Signal transduction systems are essential for microorganisms to respond to their ever-changing environment. They can be distinguished into one-component systems, two-component systems, and extracytoplasmic-function σ factors. Abundances of a few signal-transducing proteins, termed herein as sensory proteins (SPs), have previously been reported to be correlated with the genome size and ecological niche of certain Gram-positive bacteria. No such reports are available for Gram-negative bacteria. The current study attempts to investigate the relationship of the abundances of SPs to genome size in Escherichia coli, and the bacterial pathotypes or phylotypes. While the relationship between SP abundance and genome size could not be established, the sensory protein index (SPI), a new metric defined herein, was found to be correlated with E. coli virulence. In addition, significant association was observed among the distribution of SPs and E. coli pathotypes. Results indicate that such associations might be due to genomic rearrangements to best utilize the resources available in a given ecological niche. Overall, the study provides an in-depth analysis of the occurrence of different SPs among pathogenic and nonpathogenic E. coli strains. Possibilities of using the SPI as a marker for identifying pathogenic strains from among an organism complex are also discussed. IMPORTANCE Sensory proteins (SPs) act as sensors and actuators for a cell and participate in important mechanisms pertaining to bacterial survival, adaptation, and virulence. Therefore, bacterial species residing in similar ecological niches or those sharing common pathotypes are expected to exhibit similar SP signatures. We have investigated profiles of SPs in different species of Escherichia coli and present in this article the sensory protein index (SPI), a metric for quantifying the abundance and/or distribution of SPs across bacterial genomes, which could indicate the virulence potency of a bacterium. The SPI could find use in characterizing uncultured strains and bacterial complexes, as a biomarker for disease diagnostics, evaluating the effect of therapeutic interventions, assessing effects of ecological alterations, etc. Grouping the studied strains of E. coli on the basis of the frequency of occurrence of SPs in their genomes could potentially replicate the stratification of these strains on the basis of their phylotypes. In addition, E. coli strains belonging to the same pathotypes were also seen to share similar SP signatures. Furthermore, the SPI was seen to be an indicator of pathogenic potency of E. coli strains. The SPI metric is expected to be useful in the (pathogenic) characterization of hereto uncultured strains which are routinely sequenced in host microbiome analysis projects, or from among an ensemble of microbial organisms constituting a biospecimen. Thus, the possibilities of using the SPI as a biomarker for diagnosis of a disease or the outcome of a therapeutic intervention cannot be ruled out. Further, SPIs obtained from longitudinal ecological samples have the potential to serve as key indicators of environmental changes. Such changes in the environment are often detrimental to the resident biome and methods for timely detection of environmental changes hold huge socioeconomic benefits.

scholarly journals Escherichia coli ATCC 8739 Adapts to the Presence of Sodium Chloride, Monosodium Glutamate, and Benzoic Acid after Extended Culture

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Chin How Lee ◽  
Jack S. H. Oon ◽  
Kun Cheng Lee ◽  
Maurice H. T. Ling
Keyword(s):  
Escherichia Coli ◽  
Sodium Chloride ◽  
Benzoic Acid ◽  
Monosodium Glutamate ◽  
Food Additives ◽  
Acid Resistance ◽  
Genetic Distances ◽  
Dissimilarity Index ◽  
E Coli ◽  
The Relationship

Escherichia coli is commonly found in intestine of human, and any changes in their adaptation or evolution may affect the human body. The relationship between E. coli and food additives is less studied as compared to antibiotics. E. coli within our human gut are consistently interacting with the food additives; thus, it is important to investigate this relationship. In this paper, we observed the evolution of E. coli cultured in different concentration of food additives (sodium chloride, benzoic acid, and monosodium glutamate), singly or in combination, over 70 passages. Adaptability over time was estimated by generation time and cell density at stationary phase. Polymerase chain reaction (PCR)/restriction fragments length polymorphism (RFLP) using 3 primers and restriction endonucleases, each was used to characterize adaptation/evolution at genomic level. The amplification and digestion profiles were tabulated and analyzed by Nei-Li dissimilarity index. Our results demonstrate that E. coli in every treatment had adapted over 465 generations. The types of stress were discovered to be different even though different concentrations of same additives were used. However, RFLP shows a convergence of genetic distances, suggesting the presence of global stress response. In addition, monosodium glutamate may be a nutrient source and support acid resistance in E. coli.

Influence of pyrolytic seeds on ZnO nanorod growth onto rigid substrates for photocatalytic abatement of Escherichia coli in water

2014 ◽  
Vol 14 (6) ◽  
pp. 1087-1094 ◽  
Author(s):  
Luis Sanchez ◽  
Lucas Guz ◽  
Pilar García ◽  
Silvia Ponce ◽  
Silvia Goyanes ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibacterial Activity ◽  
Zno Nanorods ◽  
Water Disinfection ◽  
Acetate Solution ◽  
Ethanol Mixture ◽  
E Coli ◽  
The Relationship ◽  
Nanorod Growth

ZnO nanorods (ZnO NRs) were grown on ZnO seeded fluorine doped tin oxide (FTO) substrates at low temperatures (90 °C) from Zn2+ precursors in alkaline aqueous solution. The ZnO seeds were deposited on the FTO substrate heated at 350 °C by spray pyrolysis of a zinc acetate solution in a water ethanol mixture. The structure of seeds was tuned by the ethanol water ratio, Γ, which controls the solvent evaporation rate of drops impinging the substrate. The relationship between the microstructure and optical properties of the ZnO NR films and the photocatalytic antibacterial activity for Escherichia coli abatement, was determined through a detailed characterization of the material. The higher photocatalytic antibacterial activity was performed by ZnO NR films grown on seeds deposited from solutions with Γ in the 0.0–0.03 range. With these films, the population of viable E. coli dropped more than six orders, from 8 × 108 to 4 × 102 CFU. These results show the potential of these materials in water disinfection.

scholarly journals The effects of partial and selective reduction in the components of the proton-motive force on lactose uptake in Escherichia coli

1981 ◽  
Vol 200 (3) ◽  
pp. 583-589 ◽  
Author(s):  
S Ahmed ◽  
I R Booth
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Membrane Potential ◽  
Selective Reduction ◽  
Proton Motive Force ◽  
Motive Force ◽  
Ph Gradient ◽  
A Value ◽  
The Relationship ◽  
Lactose Transport

The relationship between the steady state lactose accumulation (delta plac) and the magnitude of the membrane potential (delta psi) and pH gradient (delta pH) has been studied at pHo5.5 and pHo7.5. An attempt has been made to differentiate between two possible means by which lactose accumulation may be reduced below the proton-motive force (delta p). Firstly, that delta psi and delta pH are not equivalent in driving lactose transport and secondly, that ‘slip’ reactions (beta-galactoside exit via the carrier without a proton) may reduce accumulation. The data support the latter; however, our conclusions are tempered by the observation that the apparent stoichiometry (delta plac/delta p) increases to a value of at least 2 at values of delta p below 130 mV.

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