scholarly journals The Antimicrobial Mechanism of Action of Epsilon-Poly-l-Lysine

2014 ◽  
Vol 80 (24) ◽  
pp. 7758-7770 ◽  
Author(s):  
Morten Hyldgaard ◽  
Tina Mygind ◽  
Brian S. Vad ◽  
Marcel Stenvang ◽  
Daniel E. Otzen ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Mechanism Of Action ◽  
Cell Morphology ◽  
Morphological Changes ◽  
Divalent Cations ◽  
Membrane Integrity ◽  
Model Organisms ◽  
Microscopy Imaging ◽  
Content Type ◽  
E Coli

ABSTRACTEpsilon-poly-l-lysine (ε-PL) is a natural antimicrobial cationic peptide which is generally regarded as safe (GRAS) as a food preservative. Although its antimicrobial activity is well documented, its mechanism of action is only vaguely described. The aim of this study was to clarify ε-PL's mechanism of action usingEscherichia coliandListeria innocuaas model organisms. We examined ε-PL's effect on cell morphology and membrane integrity and used an array ofE. colideletion mutants to study how specific outer membrane components affected the action of ε-PL. We furthermore studied its interaction with lipid bilayers using membrane models.In vitrocell studies indicated that divalent cations and the heptose I and II phosphate groups in the lipopolysaccharide layer ofE. coliare critical for ε-PL's binding efficiency. ε-PL removed the lipopolysaccharide layer and affected cell morphology ofE. coli, whileL. innocuaunderwent minor morphological changes. Propidium iodide staining showed that ε-PL permeabilized the cytoplasmic membrane in both species, indicating the membrane as the site of attack. We compared the interaction with neutral or negatively charged membrane systems and showed that the interaction with ε-PL relied on negative charges on the membrane. Suspended membrane vesicles were disrupted by ε-PL, and a detergent-like disruption ofE. colimembrane was confirmed by atomic force microscopy imaging of supported lipid bilayers. We hypothesize that ε-PL destabilizes membranes in a carpet-like mechanism by interacting with negatively charged phospholipid head groups, which displace divalent cations and enforce a negative curvature folding on membranes that leads to formation of vesicles/micelles.

scholarly journals Effect of Essential Oils on Growth Inhibition, Biofilm Formation and Membrane Integrity of Escherichia coli and Staphylococcus aureus

Antibiotics ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1474
Author(s):  
Andrés Martínez ◽  
Marcela Manrique-Moreno ◽  
Maria C. Klaiss-Luna ◽  
Elena Stashenko ◽  
German Zafra ◽  
...  
Keyword(s):  
Essential Oils ◽  
Lipid Bilayers ◽  
Biofilm Formation ◽  
Method Development ◽  
Membrane Integrity ◽  
Thymus Vulgaris ◽  
Hydrophobic Core ◽  
Synthetic Membranes ◽  
E Coli ◽  
Microdilution Method

Biofilm as a cellular conformation confers survival properties to microbial populations and favors microbial resistance. Here, we investigated the antimicrobial, antibiofilm, antimotility, antihemolytic activity, and the interaction with synthetic membranes of 15 essential oils (EOs) on E. coli ATCC 25922 and S. aureus ATCC 29213. Antimicrobial activity of EOs was determined through microdilution method; development of the biofilm was assessed using the crystal violet assay and SEM microscopy. Results indicate that Lippia origanoides thymol–carvacrol II chemotype (LTC II) and Thymus vulgaris (TV) exhibited a significant antibacterial activity, with MIC values of 0.45 and 0.75 mg/mL, respectively. The percentage of biofilm formation inhibition was greater than 70% at subinhibitory concentrations (MIC50) for LTC II EO. The results demonstrate that these two oils had significantly reduced the hemolytic effect of S. aureus by 54% and 32%, respectively, and the mobility capacity by swimming in E. coli with percentages of decrease of 55% and 47%, respectively. The results show that LTC II and TV EOs can interact with the hydrophobic core of lipid bilayers and alter the physicochemical properties of membranes. The findings suggest that LTC II and TV oils may potentially be used to aid in the treatment of S. aureus and E. coli infections.

scholarly journals Effect of Long-Term Starvation on the Survival, Recovery, and Carbon Utilization Profiles of a Bovine Escherichia coli O157:H7 Isolate from New Zealand

2014 ◽  
Vol 80 (14) ◽  
pp. 4383-4390 ◽  
Author(s):  
Ron N. Xavier ◽  
Hugh W. Morgan ◽  
Ian R. McDonald ◽  
Helen Withers
Keyword(s):  
Escherichia Coli ◽  
New Zealand ◽  
Membrane Integrity ◽  
Nutrient Level ◽  
Carbon Utilization ◽  
Content Type ◽  
E Coli ◽  
Significant Difference ◽  
Carbon Utilization Profiles ◽  
Phosphate Buffered Saline

ABSTRACTThe ability to maintain a dual lifestyle of colonizing the ruminant gut and surviving in nonhost environments once shed is key to the success ofEscherichia coliO157:H7 as a zoonotic pathogen. Both physical and biological conditions encountered by the bacteria are likely to change during the transition between host and nonhost environments. In this study, carbon starvation at suboptimal temperatures in nonhost environments was simulated by starving a New Zealand bovineE. coliO157:H7 isolate in phosphate-buffered saline at 4 and 15°C for 84 days. Recovery of starved cells on media with different nutrient availabilities was monitored under aerobic and anaerobic conditions. We found that the New Zealand bovineE. coliO157:H7 isolate was able to maintain membrane integrity and viability over 84 days and that the level of recovery depended on the nutrient level of the recovery medium as well as the starvation temperature. In addition, a significant difference in carbon utilization was observed between starved and nonstarved cells.

scholarly journals Dynamic Mechanisms of the Bactericidal Action of an Al2O3-TiO2-Ag Granular Material on an Escherichia coli Strain

2015 ◽  
Vol 81 (20) ◽  
pp. 7135-7142 ◽  
Author(s):  
Marie-Anne Tartanson ◽  
Laurence Soussan ◽  
Matthieu Rivallin ◽  
Sophie Pecastaings ◽  
Cristian V. Chis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Granular Material ◽  
Morphological Changes ◽  
Membrane Damage ◽  
Coli Strain ◽  
Cell Integrity ◽  
Bactericidal Action ◽  
Intact Cells ◽  
Content Type ◽  
E Coli

ABSTRACTThe bactericidal activity of an Al2O3-TiO2-Ag granular material against anEscherichia colistrain was confirmed by a culture-based method. In particular, 100% of microorganisms were permanently inactivated in 30 to 45 min. The present work aimed to investigate the mechanisms of the bactericidal action of this material and their dynamics onEscherichia coliusing different techniques. Observations by transmission electron microscopy (TEM) at different times of disinfection revealed morphological changes in the bacteria as soon as they were put in contact with the material. Notably highlighted were cell membrane damage; cytoplasm detachment; formation of vacuoles, possibly due to DNA condensation, in association with regions exhibiting different levels of electron density; and membrane lysis. PCR and flow cytometry analyses were used to confirm and quantify the observations of cell integrity. The direct exposure of cells to silver, combined with the oxidative stress induced by the reactive oxygen species (ROS) generated, was identified to be responsible for these morphological alterations. From the first 5 min of treatment with the Al2O3-TiO2-Ag material, 98% ofE. coliisolates were lysed. From 30 min, cell viability decreased to reach total inactivation, although approximately 1% of permeableE. colicells and 1% of intact cells (105genomic units · ml−1) were evidenced. This study demonstrates that the bactericidal effect of the material results from a synergic action of desorbed and supported silver. Supported silver was shown to generate the ROS evidenced.

scholarly journals Novel Translation Initiation Regulation Mechanism in Escherichia coli ptrB Mediated by a 5′-Terminal AUG

2017 ◽  
Vol 199 (14) ◽  
Author(s):  
Heather J. Beck ◽  
Gary R. Janssen
Keyword(s):  
Escherichia Coli ◽  
Translation Initiation ◽  
Translational Regulation ◽  
Current Knowledge ◽  
Upstream Open Reading Frame ◽  
Model Organisms ◽  
Regulation Mechanism ◽  
Rna Regulation ◽  
Content Type ◽  
E Coli

ABSTRACT Alternative translation initiation mechanisms, distinct from the Shine-Dalgarno (SD) sequence-dependent mechanism, are more prevalent in bacteria than once anticipated. Translation of Escherichia coli ptrB instead requires an AUG triplet at the 5′ terminus of its mRNA. The 5′-terminal AUG (5′-uAUG) acts as a ribosomal recognition signal to attract ribosomes to the ptrB mRNA rather than functioning as an initiation codon to support translation of an upstream open reading frame. ptrB expression exhibits a stronger dependence on the 5′-uAUG than the predicted SD sequence; however, strengthening the predicted ptrB SD sequence relieves the necessity for the 5′-uAUG. Additional sequences within the ptrB 5′ untranslated region (5′-UTR) work cumulatively with the 5′-uAUG to control expression of the downstream ptrB coding sequence (CDS), thereby compensating for the weak SD sequence. Replacement of 5′-UTRs from other mRNAs with the ptrB 5′-UTR sequence showed a similar dependence on the 5′-uAUG for CDS expression, suggesting that the regulatory features contained within the ptrB 5′-UTR are sufficient to control the expression of other E. coli CDSs. Demonstration that the 5′-uAUG present on the ptrB leader mRNA is involved in ribosome binding and expression of the downstream ptrB CDS revealed a novel form of translational regulation. Due to the abundance of AUG triplets at the 5′ termini of E. coli mRNAs and the ability of ptrB 5′-UTR regulation to function independently of gene context, the regulatory effects of 5′-uAUGs on downstream CDSs may be widespread throughout the E. coli genome. IMPORTANCE As the field of synthetic biology continues to grow, a complete understanding of basic biological principles will be necessary. The increasing complexity of the synthetic systems highlights the gaps in our current knowledge of RNA regulation. This study demonstrates that there are novel ways to regulate canonical Shine-Dalgarno-led mRNAs in Escherichia coli, illustrating that our understanding of the fundamental processes of translation and RNA regulation is still incomplete. Even for E. coli, one of the most-studied model organisms, genes with translation initiation mechanisms that do not fit the canonical Shine-Dalgarno sequence paradigm are being revealed. Uncovering diverse mechanisms that control translational expression will allow synthetic biologists to finely tune protein production of desired gene products.

scholarly journals Overcoming Iron Deficiency of anEscherichia colitonBMutant by Increasing Outer Membrane Permeability

2019 ◽  
Vol 201 (17) ◽  
Author(s):  
Nan Qiu ◽  
Rajeev Misra
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Membrane Integrity ◽  
Receptor Protein ◽  
Permeability Barrier ◽  
Prolonged Incubation ◽  
Content Type ◽  
E Coli ◽  
Outer Membrane Permeability

ABSTRACTThe intake of certain nutrients, including ferric ion, is facilitated by the outer membrane-localized transporters. Due to ferric insolubility at physiological pH,Escherichia colisecretes a chelator, enterobactin, outside the cell and then transports back the enterobactin-ferric complex via an outer membrane receptor protein, FepA, whose activity is dependent on the proton motive force energy transduced by the TonB-ExbBD complex of the inner membrane. Consequently, ΔtonBmutant cells grow poorly on a medium low in iron. Prolonged incubation of ΔtonBcells on low-iron medium yields faster-growing colonies that acquired suppressor mutations in theyejM(pbgA) gene, which codes for a putative inner-to-outer membrane cardiolipin transporter. Further characterization of suppressors revealed that they display hypersusceptibility to vancomycin, a large hydrophilic antibiotic normally precluded from enteringE. colicells, and leak periplasmic proteins into the culture supernatant, indicating a compromised outer membrane permeability barrier. All phenotypes were reversed by supplying the wild-type copy ofyejMon a plasmid, suggesting thatyejMmutations are solely responsible for the observed phenotypes. The deletion of all known cardiolipin synthase genes (clsABC) did not produce the phenotypes similar to mutations in theyejMgene, suggesting that the absence of cardiolipin from the outer membraneper seis not responsible for increased outer membrane permeability. Elevated lysophosphatidylethanolamine levels and the synthetic growth phenotype withoutpldAindicated that defective lipid homeostasis in theyejMmutant compromises outer membrane lipid asymmetry and permeability barrier to allow enterobactin intake, and that YejM has additional roles other than transporting cardiolipin.IMPORTANCEThe work presented here describes a positive genetic selection strategy for isolating mutations that destabilize the outer membrane permeability barrier ofE. coli. Given the importance of the outer membrane in restricting the entry of antibiotics, characterization of the genes and their products that affect outer membrane integrity will enhance the understanding of bacterial membranes and the development of strategies to bypass the outer membrane barrier for improved drug efficacy.

scholarly journals Antibacterial Mechanism of Action of Arylamide Foldamers

2011 ◽  
Vol 55 (11) ◽  
pp. 5043-5053 ◽  
Author(s):  
Bruk Mensa ◽  
Yong Ho Kim ◽  
Sungwook Choi ◽  
Richard Scott ◽  
Gregory A. Caputo ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Mechanism Of Action ◽  
Morphological Changes ◽  
Transcriptional Profiling ◽  
Polymyxin B ◽  
Content Type ◽  
Oxidative Stresses ◽  
Bacterial Cell Death ◽  
Arylamide Foldamers ◽  
Time Required

ABSTRACTSmall arylamide foldamers designed to mimic the amphiphilic nature of antimicrobial peptides (AMPs) have shown potent bactericidal activity against both Gram-negative and Gram-positive strains without many of the drawbacks of natural AMPs. These foldamers were shown to cause large changes in the permeability of the outer membrane ofEscherichia coli. They cause more limited permeabilization of the inner membrane which reaches critical levels corresponding with the time required to bring about bacterial cell death. Transcriptional profiling ofE. colitreated with sublethal concentrations of the arylamides showed induction of genes related to membrane and oxidative stresses, with some overlap with the effects observed for polymyxin B. Protein secretion into the periplasm and the outer membrane is also compromised, possibly contributing to the lethality of the arylamide compounds. The induction of membrane stress response regulons such asrcscoupled with morphological changes at the membrane observed by electron microscopy suggests that the activity of the arylamides at the membrane represents a significant contribution to their mechanism of action.

scholarly journals Antimicrobial Mechanism of Monocaprylate

2012 ◽  
Vol 78 (8) ◽  
pp. 2957-2965 ◽  
Author(s):  
Morten Hyldgaard ◽  
Duncan S. Sutherland ◽  
Maria Sundh ◽  
Tina Mygind ◽  
Rikke Louise Meyer
Keyword(s):  
Lipid Bilayers ◽  
Cell Structure ◽  
Membrane Integrity ◽  
Membrane Vesicles ◽  
Antimicrobial Effect ◽  
Threshold Concentration ◽  
Content Type ◽  
Force Microscopy ◽  
Calcein Leakage ◽  
A Site

ABSTRACTMonoglyceride esters of fatty acids occur naturally and encompass a broad spectrum of antimicrobial activity. Monocaprylate is generally regarded as safe (GRAS) and can function both as an emulsifier and as a preservative in food. However, knowledge about its mode of action is lacking. The aim of this study was therefore to elucidate the mechanism behind monocaprylate's antimicrobial effect. The cause of cell death inEscherichia coli,Staphylococcus xylosus, andZygosaccharomyces bailiiwas investigated by examining monocaprylate's effect on cell structure, membrane integrity, and its interaction with model membranes. Changes in cell structure were visible by atomic force microscopy (AFM), and propidium iodide staining showed membrane disruption, indicating the membrane as a site of action. This indication was confirmed by measuring calcein leakage from membrane vesicles exposed to monocaprylate. AFM imaging of supported lipid bilayers visualized the integration of monocaprylate into the liquid disordered, and not the solid ordered, phase of the membrane. The integration of monocaprylate was confirmed by quartz crystal microbalance measurements, showing an abrupt increase in mass and hydration of the membrane after exposure to monocaprylate above a threshold concentration. We hypothesize that monocaprylate destabilizes membranes by increasing membrane fluidity and the number of phase boundary defects. The sensitivity of cells to monocaprylate will therefore depend on the lipid composition, fluidity, and curvature of the membrane.

scholarly journals Phenotypic Profiling of Antibiotic Response Signatures in Escherichia coli Using Raman Spectroscopy

2013 ◽  
Vol 58 (3) ◽  
pp. 1302-1314 ◽  
Author(s):  
A. I. M. Athamneh ◽  
R. A. Alajlouni ◽  
R. S. Wallace ◽  
M. N. Seleem ◽  
R. S. Senger
Keyword(s):  
Escherichia Coli ◽  
Raman Spectroscopy ◽  
Mechanism Of Action ◽  
Excitation Wavelength ◽  
Label Free ◽  
Analysis Model ◽  
Content Type ◽  
E Coli ◽  
Antibiotic Drug ◽  
Drug Development Research

ABSTRACTIdentifying the mechanism of action of new potential antibiotics is a necessary but time-consuming and costly process. Phenotypic profiling has been utilized effectively to facilitate the discovery of the mechanism of action and molecular targets of uncharacterized drugs. In this research, Raman spectroscopy was used to profile the phenotypic response ofEscherichia colito applied antibiotics. The use of Raman spectroscopy is advantageous because it is noninvasive, label free, and prone to automation, and its results can be obtained in real time. In this research,E. colicultures were subjected to three times the MICs of 15 different antibiotics (representing five functional antibiotic classes) with known mechanisms of action for 30 min before being analyzed by Raman spectroscopy (using a 532-nm excitation wavelength). The resulting Raman spectra contained sufficient biochemical information to distinguish between profiles induced by individual antibiotics belonging to the same class. The collected spectral data were used to build a discriminant analysis model that identified the effects of unknown antibiotic compounds on the phenotype ofE. colicultures. Chemometric analysis showed the ability of Raman spectroscopy to predict the functional class of an unknown antibiotic and to identify individual antibiotics that elicit similar phenotypic responses. Results of this research demonstrate the power of Raman spectroscopy as a cellular phenotypic profiling methodology and its potential impact on antibiotic drug development research.

scholarly journals Mechanism of Action of the Arylomycin Antibiotics and Effects of Signal Peptidase I Inhibition

2012 ◽  
Vol 56 (10) ◽  
pp. 5054-5060 ◽  
Author(s):  
Peter A. Smith ◽  
Floyd E. Romesberg
Keyword(s):  
Secretory Pathway ◽  
Signal Peptidase ◽  
Model Organisms ◽  
Type I ◽  
Content Type ◽  
E Coli ◽  
Secretion Pathway ◽  
Secretion Stress ◽  
Signal Peptidase I ◽  
Essential Enzyme

ABSTRACTClinically approved antibiotics inhibit only a small number of conserved pathways that are essential for bacterial viability, and the physiological effects of inhibiting these pathways have been studied in great detail. Likewise, characterizing the effects of candidate antibiotics that function via novel mechanisms of action is critical for their development, which is of increasing importance due to the ever-growing problem of resistance. The arylomycins are a novel class of natural-product antibiotics that act via the inhibition of type I signal peptidase (SPase), which is an essential enzyme that functions as part of the general secretory pathway and is not the target of any clinically deployed antibiotic. Correspondingly, little is known about the effects of SPase inhibition or how bacteria may respond to mitigate the associated secretion stress. Using genetically sensitizedEscherichia coliandStaphylococcus aureusas model organisms, we examine the activity of arylomycin as a function of its concentration, bacterial cell density, target expression levels, and bacterial growth phase. The results reveal that the activity of the arylomycins results from an insufficient flux of proteins through the secretion pathway and the resulting mislocalization of proteins. Interestingly, this has profoundly different effects onE. coliandS. aureus. Finally, we examine the activity of arylomycin in combination with distinct classes of antibiotics and demonstrate that SPase inhibition results in synergistic sensitivity when combined with an aminoglycoside.

scholarly journals Specific Electromagnetic Effects of Microwave Radiation on Escherichia coli

2011 ◽  
Vol 77 (9) ◽  
pp. 3017-3022 ◽  
Author(s):  
Yury Shamis ◽  
Alex Taube ◽  
Natasa Mitik-Dineva ◽  
Rodney Croft ◽  
Russell J. Crawford ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Membrane ◽  
Cell Morphology ◽  
Laser Scanning ◽  
Simulation Software ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Bacterial Cells ◽  
Content Type ◽  
E Coli

ABSTRACTThe present study investigated the effects of microwave (MW) radiation applied under a sublethal temperature onEscherichia coli. The experiments were conducted at a frequency of 18 GHz and at a temperature below 40°C to avoid the thermal degradation of bacterial cells during exposure. The absorbed power was calculated to be 1,500 kW/m3, and the electric field was determined to be 300 V/m. Both values were theoretically confirmed using CST Microwave Studio 3D Electromagnetic Simulation Software. As a negative control,E. colicells were also thermally heated to temperatures up to 40°C using Peltier plate heating. Scanning electron microscopy (SEM) analysis performed immediately after MW exposure revealed that theE. colicells exhibited a cell morphology significantly different from that of the negative controls. This MW effect, however, appeared to be temporary, as following a further 10-min elapsed period, the cell morphology appeared to revert to a state that was identical to that of the untreated controls. Confocal laser scanning microscopy (CLSM) revealed that fluorescein isothiocyanate (FITC)-conjugated dextran (150 kDa) was taken up by the MW-treated cells, suggesting that pores had formed within the cell membrane. Cell viability experiments revealed that the MW treatment was not bactericidal, since 88% of the cells were recovered after radiation. It is proposed that one of the effects of exposingE. colicells to MW radiation under sublethal temperature conditions is that the cell surface undergoes a modification that is electrokinetic in nature, resulting in a reversible MW-induced poration of the cell membrane.

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