scholarly journals Lentivirus Lytic Peptide 1 Perturbs both Outer and Inner Membranes of Serratia marcescens

2002 ◽  
Vol 46 (6) ◽  
pp. 2041-2045 ◽  
Author(s):  
Shruti M. Phadke ◽  
Vanja Lazarevic ◽  
Caroline C. Bahr ◽  
Kazi Islam ◽  
Donna Beer Stolz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Antimicrobial Peptides ◽  
Serratia Marcescens ◽  
Outer Membrane ◽  
Polymyxin B ◽  
Mechanisms Of Action ◽  
Lytic Peptide ◽  
Bacterial Membranes ◽  
Lentivirus Lytic Peptide

ABSTRACT Bis-lentivirus lytic protein 1 (Bis-LLP1) and polymyxin B exhibited similar killing activities against Serratia marcescens. By electron microscopy, bis-LLP1 interacted with the outer and cytoplasmic bacterial membranes, while polymyxin B affected only the outer membrane. The results of standard biochemical probes supported the findings of the electron microscopy studies, suggesting that these antimicrobial peptides have different mechanisms of action.

scholarly journals Antimicrobial Peptides: Mechanisms of Action and Resistance

2016 ◽  
Vol 96 (3) ◽  
pp. 254-260 ◽  
Author(s):  
B. Bechinger ◽  
S.-U. Gorr
Keyword(s):  
Cell Wall ◽  
Cell Membrane ◽  
Antimicrobial Peptides ◽  
Bacterial Resistance ◽  
Rare Event ◽  
Mechanisms Of Action ◽  
Current Evidence ◽  
Aggregation State ◽  
Host Defense Peptides ◽  
Bacterial Membranes

More than 40 antimicrobial peptides and proteins (AMPs) are expressed in the oral cavity. These AMPs have been organized into 6 functional groups, 1 of which, cationic AMPs, has received extensive attention in recent years for their promise as potential antibiotics. The goal of this review is to describe recent advances in our understanding of the diverse mechanisms of action of cationic AMPs and the bacterial resistance against these peptides. The recently developed peptide GL13K is used as an example to illustrate many of the discussed concepts. Cationic AMPs typically exhibit an amphipathic conformation, which allows increased interaction with negatively charged bacterial membranes. Peptides undergo changes in conformation and aggregation state in the presence of membranes; conversely, lipid conformation and packing can adapt to the presence of peptides. As a consequence, a single peptide can act through several mechanisms depending on the peptide’s structure, the peptide:lipid ratio, and the properties of the lipid membrane. Accumulating evidence shows that in addition to acting at the cell membrane, AMPs may act on the cell wall, inhibit protein folding or enzyme activity, or act intracellularly. Therefore, once a peptide has reached the cell wall, cell membrane, or its internal target, the difference in mechanism of action on gram-negative and gram-positive bacteria may be less pronounced than formerly assumed. While AMPs should not cause widespread resistance due to their preferential attack on the cell membrane, in cases where specific protein targets are involved, the possibility exists for genetic mutations and bacterial resistance. Indeed, the potential clinical use of AMPs has raised the concern that resistance to therapeutic AMPs could be associated with resistance to endogenous host-defense peptides. Current evidence suggests that this is a rare event that can be overcome by subtle structural modifications of an AMP.

scholarly journals The Vibrio cholerae ToxR-Regulated Porin OmpU Confers Resistance to Antimicrobial Peptides

2004 ◽  
Vol 72 (6) ◽  
pp. 3577-3583 ◽  
Author(s):  
Jyoti Mathur ◽  
Matthew K. Waldor
Keyword(s):  
Antimicrobial Peptides ◽  
Outer Membrane ◽  
Vibrio Cholerae ◽  
Surface Protein ◽  
Polymyxin B ◽  
Common Mechanism ◽  
Antimicrobial Protein ◽  
Wild Type ◽  
Human Gastrointestinal Tract ◽  
Serovar Typhimurium

ABSTRACT BPI (bactericidal/permeability-increasing) is a potent antimicrobial protein that was recently reported to be expressed as a surface protein on human gastrointestinal tract epithelial cells. In this study, we investigated the resistance of Vibrio cholerae, a small-bowel pathogen that causes cholera, to a BPI-derived peptide, P2. Unlike in Escherichia coli and Salmonella enterica serovar Typhimurium, resistance to P2 in V. cholerae was not dependent on the BipA GTPase. Instead, we found that ToxR, the master regulator of V. cholerae pathogenicity, controlled resistance to P2 by regulating the production of the outer membrane protein OmpU. Both toxR and ompU mutants were at least 100-fold more sensitive to P2 than were wild-type cells. OmpU also conferred resistance to polymyxin B sulfate, suggesting that this porin may impart resistance to cationic antibacterial proteins via a common mechanism. Studies of stationary-phase cells revealed that the ToxR-repressed porin OmpT may also contribute to P2 resistance. Finally, although the mechanism of porin-mediated resistance to antimicrobial peptides remains elusive, our data suggest that the BPI peptide sensitivity of OmpU-deficient V. cholerae is not attributable to a generally defective outer membrane.

scholarly journals Damage of the Bacterial Cell Envelope by Antimicrobial Peptides Gramicidin S and PGLa as Revealed by Transmission and Scanning Electron Microscopy

2010 ◽  
Vol 54 (8) ◽  
pp. 3132-3142 ◽  
Author(s):  
Mareike Hartmann ◽  
Marina Berditsch ◽  
Jacques Hawecker ◽  
Mohammad Fotouhi Ardakani ◽  
Dagmar Gerthsen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Antimicrobial Peptides ◽  
Lipid Membrane ◽  
Ultrastructural Changes ◽  
Morphological Alterations ◽  
Bacterial Membranes ◽  
E Coli ◽  
Gramicidin S ◽  
Scanning Electron

ABSTRACT Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the ultrastructural changes in bacteria induced by antimicrobial peptides (AMPs). Both the β-stranded gramicidin S and the α-helical peptidyl-glycylleucine-carboxyamide (PGLa) are cationic amphiphilic AMPs known to interact with bacterial membranes. One representative Gram-negative strain, Escherichia coli ATCC 25922, and one representative Gram-positive strain, Staphylococcus aureus ATCC 25923, were exposed to the AMPs at sub-MICs and supra-MICs in salt-free medium. SEM revealed a shortening and swelling of the E. coli cells, and multiple blisters and bubbles formed on their surface. The S. aureus cells seemed to burst upon AMP exposure, showing open holes and deep craters in their envelope. TEM revealed the formation of intracellular membranous structures in both strains, which is attributed to a lateral expansion of the lipid membrane upon peptide insertion. Also, some morphological alterations in the DNA region were detected for S. aureus. After E. coli was incubated with AMPs in medium with low ionic strength, the cells appeared highly turgid compared to untreated controls. This observation suggests that the AMPs enhance osmosis through the inner membrane, before they eventually cause excessive leakage of the cellular contents. The adverse effect on the osmoregulatory capacity of the bacteria is attributed to the membrane-permeabilizing action of the amphiphilic peptides, even at low (sub-MIC) AMP concentrations. Altogether, the results demonstrate that both TEM and SEM, as well as appropriate sample preparation protocols, are needed to obtain detailed mechanistic insights into peptide function.

scholarly journals Synergistic Interaction between Silver Nanoparticles and Membrane-Permeabilizing Antimicrobial Peptides

2009 ◽  
Vol 53 (8) ◽  
pp. 3538-3540 ◽  
Author(s):  
Serge Ruden ◽  
Kai Hilpert ◽  
Marina Berditsch ◽  
Parvesh Wadhwani ◽  
Anne S. Ulrich
Keyword(s):  
Silver Nanoparticles ◽  
Infectious Diseases ◽  
Antimicrobial Peptides ◽  
Synergistic Effects ◽  
Polymyxin B ◽  
Gram Negative Bacteria ◽  
Internal Target ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Target Sites

ABSTRACT Silver nanoparticles, as well as antimicrobial peptides (AMPs), can be used to fight infectious diseases. Since AMPs are known to permeabilize bacterial membranes and might therefore help silver nanoparticles to access internal target sites, we investigated their combined activities and showed synergistic effects between polymyxin B and silver nanoparticles for gram-negative bacteria.

Sensitization of Outer-Membrane Mutants of Salmonella Typhimurium and Pseudomonas aeruginosa to Antimicrobial Peptides under High Pressure

2003 ◽  
Vol 66 (8) ◽  
pp. 1360-1367 ◽  
Author(s):  
BARBARA MASSCHALCK ◽  
DAPHNE DECKERS ◽  
CHRIS W. MICHIELS
Keyword(s):  
Pseudomonas Aeruginosa ◽  
High Pressure ◽  
Antimicrobial Peptides ◽  
Salmonella Typhimurium ◽  
Outer Membrane ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Polymyxin B ◽  
Membrane Properties ◽  
Bacterial Populations ◽  
Serovar Typhimurium

High pressure can sensitize gram-negative bacteria to antimicrobial peptides or proteins through the permeabilization of their outer membranes; however, the range of compounds to which sensitivity is induced is species and strain dependent. We studied the role of outer-membrane properties in this sensitization by making use of a series of rough and deep rough mutants of Salmonella enterica serovar Typhimurium that show an increased degree of lipopolysaccharide(LPS) truncation, along with Pseudomonas aeruginosa PhoP and PhoQ mutants with altered outer-membrane properties. The outer-membrane properties of P. aeruginosa were also modulated through the use of different Mg2+ concentrations in the growth medium. Each of these strains was challenged under high pressure (15 min at 270 MPa for Salmonella Typhimurium and 15 min at 100 MPa for P. aeruginosa) in phosphate buffer with lysozyme (100 μg/ml), nisin (100 IU/ml), lactoferricin (20 μg/ml), and HEL96-116 (100 μg/ml), a synthetic lysozyme-derived peptide, and sensitization levels were compared. The results obtained indicated that outer-membrane properties affected high-pressure sensitization differently for different compounds. LPS truncation in Salmonella Typhimurium was correlated with increased sensitization to lysozyme (up to 1.5 log10 units) and nisin (up to 1.2 log10 units) but with decreased sensitization to lactoferricin under pressure. For P. aeruginosa, the pattern of sensitization to lactoferricin and nisin resembled that of polymyxin B at atmospheric pressure, suggesting that pressure induces the self-promoted uptake of both peptides. Sensitization to HEL96-116 was not affected by outer-membrane properties for either organism. Hence, outer-membrane permeabilization by high pressure cannot be explained by a single unifying mechanism and is dependent on the organism, the outer-membrane properties, and the nature of the antimicrobial compound. On the basis of these findings, the use of antimicrobial cocktails targeting different bacteria and fractions of bacterial populations may enhance the efficacy of high pressure as a preservation treatment.

scholarly journals Capsule Polysaccharide Mediates Bacterial Resistance to Antimicrobial Peptides

2004 ◽  
Vol 72 (12) ◽  
pp. 7107-7114 ◽  
Author(s):  
Miguel A. Campos ◽  
Miguel A. Vargas ◽  
Verónica Regueiro ◽  
Catalina M. Llompart ◽  
Sebastián Albertí ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Bacterial Resistance ◽  
Wild Type Strain ◽  
Critical Role ◽  
Polymyxin B ◽  
Innate Immune ◽  
Wild Type ◽  
Bacterial Membranes ◽  
O Antigen

ABSTRACT The innate immune system plays a critical role in the defense of areas exposed to microorganisms. There is an increasing body of evidence indicating that antimicrobial peptides and proteins (APs) are one of the most important weapons of this system and that they make up the protective front for the respiratory tract. On the other hand, it is known that pathogenic organisms have developed countermeasures to resist these agents such as reducing the net negative charge of the bacterial membranes. Here we report the characterization of a novel mechanism of resistance to APs that is dependent on the bacterial capsule polysaccharide (CPS). Klebsiella pneumoniae CPS mutant was more sensitive than the wild type to human neutrophil defensin 1, β-defensin 1, lactoferrin, protamine sulfate, and polymyxin B. K. pneumoniae lipopolysaccharide O antigen did not play an important role in AP resistance, and CPS was the only factor conferring protection against polymyxin B in strains lacking O antigen. In addition, we found a significant correlation between the amount of CPS expressed by a given strain and the resistance to polymyxin B. We also showed that K. pneumoniae CPS mutant bound more polymyxin B than the wild-type strain with a concomitant increased in the self-promoted pathway. Taken together, our results suggest that CPS protects bacteria by limiting the interaction of APs with the surface. Finally, we report that K. pneumoniae increased the amount of CPS and upregulated cps transcription when grown in the presence of polymyxin B and lactoferrin.

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