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 Extracellular Vesicle Biogenesis and Functions in Gram-Positive Bacteria

2020 ◽  
Vol 88 (12) ◽  
Author(s):  
Paul Briaud ◽  
Ronan K. Carroll
Keyword(s):  
Lipid Bilayers ◽  
Membrane Vesicles ◽  
Cell Interaction ◽  
Extracellular Vesicle ◽  
Wall Structure ◽  
Future Research ◽  
Gram Positive ◽  
Content Type ◽  
Bacterial Physiology ◽  
Gram Positive Bacteria

ABSTRACT Extracellular vesicles (EVs) are membrane-derived lipid bilayers secreted by bacteria and eukaryotic cells. Bacterial membrane vesicles were discovered over 60 years ago and have been extensively studied in Gram-negative bacteria. During their production, EVs are loaded with proteins, nucleic acids, and various compounds that are subsequently released into the environment. Depending on the packaged cargo, EVs have a broad spectrum of action and are involved in pathogenesis, antibiotic resistance, nutrient uptake, and nucleic acid transfer. Due to differences in cell wall structure, EVs in Gram-positive bacteria have been disregarded for decades, and our understanding of their biogenesis and host cell interaction is incomplete. Recently, studies on bacteria such as Staphylococcus aureus, Streptococcus spp., Bacillus subtilis, and Mycobacterium spp. have demonstrated EV production in Gram-positive bacteria and shown the great importance EVs have in Gram-positive bacterial physiology and disease progression. Here, we review the latest findings on the biogenesis and functions of EVs from Gram-positive bacteria and identify key areas for future research.

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.

“The cut and thrust of industrial relations” – bullying by another name?

2018 ◽  
Vol 33 (1) ◽  
pp. 2-13 ◽  
Author(s):  
Pat Drake
Keyword(s):  
Women Leaders ◽  
Industrial Relations ◽  
Illustrative Case ◽  
University Leadership ◽  
Public Identity ◽  
Content Type ◽  
Female Self ◽  
Emotional Work ◽  
Differences Of Opinion ◽  
A Site

Purpose The purpose of this paper is to offer a feminography, that is a “narration of a female self in a feminist age” (Abrams, 2017) by presenting a conceptual analysis, derived from experience, of email providing a form of discourse – that the author calls finger-speak – through which unexamined gender positioning caricatures a person’s identity. In so doing, the paper provides an illustrative case of a female manager being positioned through email to “know her place, perform it and feel it” (Hey, 2011). Design/methodology/approach An analysis of email foregrounds “finger-speak” as a form of digital conversation and through which people in universities may be positioned publicly but without their consent in relation to unexamined norms and assumptions. For women, it is argued, these norms are ageist and sexist. In this paper, fragments of finger-speak are collated to provide a reading of how mixing gendered norms with apparent differences of opinion constructs, via unexamined sexism, a public identity and then undermines it. Findings Through the case presented, the author argues that, because of a shared but unarticulated shadow over women as leaders, email lays the ground for subsequent scapegoating in such a manner that the woman takes responsibility for structural challenges that rightly belong to the organisation. Originality/value The contribution that email makes to constructing female identity in public is new, complementing other work that publicly characterises women leaders, through film (Ezzedeen, 2015), and through published writing such as autobiography (Kapasi et al., 2016). Emotional work undertaken by women in university leadership is so far under-represented in public, and email is a site through which this work becomes visible.

scholarly journals Antibacterial Properties of Plasma-Activated Perfluorinated Substrates with Silver Nanoclusters Deposition

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 182
Author(s):  
Petr Slepička ◽  
Silvie Rimpelová ◽  
Nikola Slepičková Kasálková ◽  
Dominik Fajstavr ◽  
Petr Sajdl ◽  
...  
Keyword(s):  
Surface Properties ◽  
Antibacterial Properties ◽  
Argon Plasma ◽  
Antimicrobial Effect ◽  
Silver Nanoclusters ◽  
Plasma Modification ◽  
Material Surface ◽  
Silver Deposition ◽  
Force Microscopy ◽  
Atomic Force

This article is focused on the evaluation of surface properties of polytetrafluoroethylene (PTFE) nanotextile and a tetrafluoroethylene-perfluoro(alkoxy vinyl ether) (PFA) film and their surface activation with argon plasma treatment followed with silver nanoclusters deposition. Samples were subjected to plasma modification for a different time exposure, silver deposition for different time periods, or their combination. As an alternative approach, the foils were coated with poly-L-lactic acid (PLLA) and silver. The following methods were used to study the surface properties of the polymers: goniometry, atomic force microscopy, and X-ray photoelectron microscopy. By combining the aforementioned methods for material surface modification, substrates with antibacterial properties eliminating the growth of Gram-positive and Gram-negative bacteria were prepared. Studies of antimicrobial activity showed that PTFE plasma-modified samples coated with PLLA and deposited with a thin layer of Ag had a strong antimicrobial effect, which was also observed for the PFA material against the bacterial strain of S. aureus. Significant antibacterial effect against S. aureus, Proteus sp. and E. coli has been demonstrated on PTFE nanotextile plasma-treated for 240 s, coated with PLLA, and subsequently sputtered with thin Ag layer.

scholarly journals A Cronobacter turicensis O1 Antigen-Specific Monoclonal Antibody Inhibits Bacterial Motility and Entry into Epithelial Cells

2014 ◽  
Vol 83 (3) ◽  
pp. 876-887 ◽  
Author(s):  
Kristina Schauer ◽  
Angelika Lehner ◽  
Richard Dietrich ◽  
Ina Kleinsteuber ◽  
Rocío Canals ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Epithelial Cells ◽  
Foodborne Pathogen ◽  
Antimicrobial Effect ◽  
Infection Model ◽  
Cell Agglutination ◽  
Content Type ◽  
O Antigen ◽  
Lethal Infection ◽  
Insight Into

Cronobacter turicensisis an opportunistic foodborne pathogen that can cause a rare but sometimes lethal infection in neonates. Little is known about the virulence mechanisms and intracellular lifestyle of this pathogen. In this study, we developed an IgG monoclonal antibody (MAb; MAb 2G4) that specifically recognizes the O1 antigen ofC. turicensiscells. The antilipopolysaccharide antibody bound predominantly monovalently to the O antigen and reduced bacterial growth without causing cell agglutination. Furthermore, binding of the antibody to the O1 antigen ofC. turicensiscells caused a significant reduction of the membrane potential which is required to energize flagellar rotation, accompanied by a decreased flagellum-based motility. These results indicate that binding of IgG to the O antigen ofC. turicensiscauses a direct antimicrobial effect. In addition, this feature of the antibody enabled new insight into the pathogenicity ofC. turicensis. In a tissue culture infection model, pretreatment ofC. turicensiswith MAb 2G4 showed no difference in adhesion to human epithelial cells, whereas invasion of bacteria into Caco-2 cells was significantly inhibited.

Diagnosis of spontaneous intracranial hypotension by using magnetic resonance myelography

2000 ◽  
Vol 92 (5) ◽  
pp. 873-876 ◽  
Author(s):  
Akira Matsumura ◽  
Izumi Anno ◽  
Hiroshi Kimura ◽  
Eiichi Ishikawa ◽  
Tadao Nose
Keyword(s):  
Magnetic Resonance ◽  
Intracranial Hypotension ◽  
Direct Evidence ◽  
Spontaneous Intracranial Hypotension ◽  
Content Type ◽  
Highly Sensitive ◽  
Csf Leakage ◽  
Leakage Site ◽  
A Site ◽  
Mr Myelography

✓ The authors describe a case of spontaneous intracranial hypotension in which the leakage site was determined by using magnetic resonance (MR) myelography. This technique demonstrated the route of cerebrospinal fluid (CSF) leakage, whereas other methods failed to show direct evidence of leakage. Magnetic resonance myelography is a noninvasive method that is highly sensitive in detecting CSF leakage. This is the first report in which a site of CSF leakage was detected using MR myelography.

Effect of Diamagnetic A2+ Substitution on the Magnetic and Ferroelectric Properties of the Bi1−xAxFeO3 Multiferroics

2007 ◽  
Vol 1034 ◽  
Author(s):  
V. A. Khomchenko ◽  
D. A. Kiselev ◽  
J. M. Vieira ◽  
Li Jian ◽  
A. M. L. Lopes ◽  
...  
Keyword(s):  
Spin Structure ◽  
Ionic Radius ◽  
Ferroelectric Properties ◽  
Piezoresponse Force Microscopy ◽  
Weak Ferromagnetism ◽  
Force Microscopy ◽  
Microscopy Data ◽  
A Site ◽  
Induced Changes ◽  
Spiral Spin

AbstractInvestigation of crystal structure, magnetic and local ferroelectric properties of the diamagnetically-doped Bi1−xAxFeO3 (A= Ca, Sr, Pb, Ba; x= 0.2, 0.3) ceramic samples has been carried out. It has been shown that the solid solutions have a rhombohedrally distorted perovskite structure described by the space group R3c. Piezoresponse force microscopy data have revealed the existence of the spontaneous ferroelectric polarization in the samples at room temperature. Magnetization measurements have shown that the magnetic state of these compounds is determined by the ionic radius of the substituting elements. A-site substitution with the biggest ionic radius ions has been found to suppress the spiral spin structure of BiFeO3 and to result in the appearance of weak ferromagnetism. The magnetic properties have been discussed in terms of doping- induced changes in the magnetic anisotropy.

scholarly journals Intracellular and Extracellular Expression of Bacillus thuringiensis Crystal Protein Cry5B in Lactococcus lactis for Use as an Anthelminthic

2015 ◽  
Vol 82 (4) ◽  
pp. 1286-1294 ◽  
Author(s):  
Evelyn Durmaz ◽  
Yan Hu ◽  
Raffi V. Aroian ◽  
Todd R. Klaenhammer
Keyword(s):  
Bacillus Thuringiensis ◽  
Lactococcus Lactis ◽  
Copy Number ◽  
Oral Delivery ◽  
Membrane Integrity ◽  
Biologically Active ◽  
High Copy Number ◽  
Cry Protein ◽  
Western Blots ◽  
Content Type

ABSTRACTTheBacillus thuringiensiscrystal (Cry) protein Cry5B (140 kDa) and a truncated version of the protein, tCry5B (79 kDa), are lethal to nematodes. Genes encoding the two proteins were separately cloned into a high-copy-number vector with a strong constitutive promoter (pTRK593) inLactococcus lactisfor potential oral delivery against parasitic nematode infections. Western blots using a Cry5B-specific antibody revealed that constitutively expressed Cry5B and tCry5B were present in both cells and supernatants. To increase production,cry5Bwas cloned into the high-copy-number plasmid pMSP3535H3, carrying a nisin-inducible promoter. Immunoblotting revealed that 3 h after nisin induction, intracellular Cry5B was strongly induced at 200 ng/ml nisin, without adversely affecting cell viability or cell membrane integrity. Both Cry5B genes were also cloned into plasmid pTRK1061, carrying a promoter and encoding a transcriptional activator that invoke low-level expression of prophage holin and lysin genes inLactococcuslysogens, resulting in a leaky phenotype. Cry5B and tCry5B were actively expressed in the lysogenic strainL. lactisKP1 and released into cell supernatants without affecting culture growth. Lactate dehydrogenase (LDH) assays indicated that Cry5B, but not LDH, leaked from the bacteria. Lastly, using intracellular lysates fromL. lactiscultures expressing both Cry5B and tCry5B,in vivochallenges ofCaenorhabditis elegansworms demonstrated that the Cry proteins were biologically active. Taken together, these results indicate that active Cry5B proteins can be expressed intracellularly in and released extracellularly fromL. lactis, showing potential for future use as an anthelminthic that could be delivered orally in a food-grade microbe.

The auditing profession and the key audit matter reporting requirement

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Dessalegn Getie Mihret ◽  
Monika Kansal ◽  
Mohammad Badrul Muttakin ◽  
Tarek Rana
Keyword(s):  
Standard Setting ◽  
International Standards ◽  
Financial Reports ◽  
Content Type ◽  
Reporting Requirement ◽  
Regulatory Rule ◽  
Rule Setting ◽  
A Site ◽  
Relationship Of

Purpose This study aims to examine the setting of International Standards on Auditing (ISA) 701 on disclosing key audit matters (KAMs) to explore the role of standard setting in maintaining or reconstituting the relationship of the auditing profession with preparers and users of financial reports. Design/methodology/approach This study draws on concepts from the sociology of the professions literature and the regulatory space metaphor. Data comprises comment letters and other documents pertaining to the setting of ISA 701. Findings The study shows that the KAM reporting requirement is part of the ongoing re-calibration of the regulatory arrangements governing auditing, which started in the early 2000s. This study interprets standard setting as a site for negotiating the relationships between linked ecologies in the audit regulatory space, namely, the auditing profession, preparers of financial statements and users of audited reports. This study identifies three processes involved in setting ISA 701, namely, reconstitution of the rules governing auditors’ reports as a link between the three ecologies, preserving boundaries between the auditing profession and preparers and negotiation aimed at balancing competing interests of the interrelated ecologies. Originality/value The study offers insights into the role of regulatory rule setting as a central medium through which the adaptive relationship of the profession with its environment is negotiated.

The role of site manager transformational leadership in the construction project success

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Zavari ◽  
Mohammad Reza Afshar
Keyword(s):  
Construction Projects ◽  
Project Success ◽  
Construction Project ◽  
Content Type ◽  
Team Innovation ◽  
Mediating Role ◽  
A Site ◽  
Site Manager ◽  
Site Managers

PurposeIn the construction industry, site managers are responsible for the day-to-day on-site running of a project. Site managers are required not only to ensure that work is done safely, on time, within budget and to the right quality standards, but also to manage any delays or problems encountered on-site during a construction project. Thus, a site manager has a significant position in the success of a construction project. However, there is a lack of studies considering the role of the leadership style of a site manager in construction project success. In this study, not only the effect of the transformational leadership (TL) style of site managers on the success of construction projects is assessed, but also the mediating role of team-building (TB) and team innovation between TL and project success is studied.Design/methodology/approachThe proposed hypotheses are tested by comparing the performance criteria of construction projects with the TL style of site managers. The success criteria of the projects are examined using project documents and client opinions, and the TL of site managers, TB aspects and team innovation in projects are assessed by asking from their subordinates. The Pearson correlation coefficient is employed to investigate the relation between every two variables.FindingsThe results illustrate that the TL of a site manager is directly related to project success; thus, the findings would confirm the importance of selecting appropriate site managers for construction projects. Moreover, while there is a mediating role of TB between TL and construction project success, team innovation does not have a mediating impact in design-bid-build (DBB) construction projects.Originality/valueAs there is a lack of studies assessing the TL effects on the success of construction projects and the significant role of site managers, this study is one of the first researches that tested these impacts and evaluated the mediating role of TB and team innovation between TL and project performance.

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