Alterations in Outer Membrane Permeability

Hancock, Robert E. W.

doi:10.1146/annurev.mi.38.100184.001321

Cited by 558 publications

(388 citation statements)

References 31 publications

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“…For P. aeruginosa, it was shown that cationic AMPs can displace divalent cations from non-covalent LPS cross-bridges, leading to destabilization and permeabilization of the outer membrane and allowing access of hydrophobic probes or lysozyme (32,47,49). This modification of the bacte- rial surface manifests in membrane blebs observable by electron microscopy (49).…”

Section: Discussionmentioning

confidence: 99%

Recognition of Pathogenic Microbes by the Drosophila Phagocytic Pattern Recognition Receptor Eater

Chung

Kocks

2011

Journal of Biological Chemistry

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Non-opsonic phagocytosis is a primordial form of pathogen recognition that is mediated by the direct interaction of phagocytic receptors with microbial surfaces. In the fruit fly Drosophila melanogaster, the EGF-like repeat containing scavenger receptor Eater is expressed by phagocytes and is required to survive infections with Gram-positive and Gram-negative bacteria. However, the mechanisms by which this receptor recognizes different types of bacteria are poorly understood. To address this problem, we generated a soluble, Fc-tagged receptor variant of Eater comprising the N-terminal 199 amino acids including four EGF-like repeats. We first established that Eater-Fc displayed specific binding to broad yet distinct classes of heat-or ethanol-inactivated microbes and behaved similarly to the membrane-bound, full-length Eater receptor. We then used Eater-Fc as a tool to probe Eater binding to the surface of live bacteria. Eater-Fc bound equally well to naive or inactivated Staphylococcus aureus or Enterococcus faecalis, suggesting that in vivo, Eater directly targets live Gram-positive bacteria, enabling their phagocytic clearance and destruction. By contrast, Eater-Fc was unable to interact with live, naive Gram-negative bacteria (Escherichia coli, Serratia marcescens, and Pseudomonas aeruginosa). For these bacteria, Eater-Fc binding required membrane-disrupting treatments. Furthermore, we found that cecropin A, a cationic, membrane-disrupting antimicrobial peptide, could promote Eater-Fc binding to live E. coli, even at sublethal concentrations. These results suggest a previously unrecognized mechanism by which antimicrobial peptides cooperate with phagocytic receptors to extend the range of microbes that can be targeted by a single, germline-encoded receptor.

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Section: Discussionmentioning

confidence: 99%

Recognition of Pathogenic Microbes by the Drosophila Phagocytic Pattern Recognition Receptor Eater

Chung

Kocks

2011

Journal of Biological Chemistry

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“…Overnight bacterial cultures were given 10-fold serial dilutions in fresh LB medium, and 10-l dilutions were transferred onto LB agar plates containing various concentrations of EDTA (1 to 2.5 M) with or without 0.5% sodium dodecyl sulfate (SDS). Colonies were counted after overnight incubation at 37°C (49,50).…”

Section: Methodsmentioning

confidence: 99%

A PhoPQ-Regulated ABC Transporter System Exports Tetracycline in Pseudomonas aeruginosa

Chen

Duan

2016

Antimicrob Agents Chemother

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bPseudomonas aeruginosa is an important human pathogen whose infections are difficult to treat due to its high intrinsic resistance to many antibiotics. Here, we show that the disruption of PA4456, encoding the ATP binding component of a putative ATP-binding cassette (ABC) transporter, increased the bacterium's susceptible to tetracycline and other antibiotics or toxic chemicals. Fluorescence spectroscopy and antibiotic accumulation tests showed that the interruption of the ABC transporter caused increased intracellular accumulation of tetracycline, demonstrating a role of the ABC transporter in tetracycline expulsion. Site-directed mutagenesis proved that the conserved residues of E170 in the Walker B motif and H203 in the H-loop, which are important for ATP hydrolysis, were essential for the function of PA4456. Through a genome-wide search, the PhoPQ twocomponent system was identified as a regulator of the computationally predicted PA4456-4452 operon that encodes the ABC transporter system. A >5-fold increase of the expression of this operon was observed in the phoQ mutant. The results obtained also show that the expression of the phzA1B1C1D1E1 operon and the production of pyocyanin were significantly higher in the ABC transporter mutant, signifying a connection between the ABC transporter and pyocyanin production. These results indicated that the PhoPQ-regulated ABC transporter is associated with intrinsic resistance to antibiotics and other adverse compounds in P. aeruginosa, probably by extruding them out of the cell.

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“…Tris-EDTA combinations of chelating agents specifically have a detrimental effect on the outer cell wall membrane of planktonic Gram-negative enteric bacteria and P. aeruginosa (59)(60)(61)(62). Membrane disruption is achieved through the chelation of divalent cations in the outer plasma membrane, which releases lipopolysaccharide (LPS) from the bacterial cell wall (63).…”

Section: Figmentioning

confidence: 99%

In Vitro Efficacy of Nonantibiotic Treatments on Biofilm Disruption of Gram-Negative Pathogens and an In Vivo Model of Infectious Endometritis Utilizing Isolates from the Equine Uterus

et al. 2016

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In this study, we evaluated the ability of the equine clinical treatments N-acetylcysteine, EDTA, and hydrogen peroxide to disrupt in vitro biofilms and kill equine reproductive pathogens (Escherichia coli, Pseudomonas aeruginosa, or Klebsiella pneumoniae) isolated from clinical cases. N-acetylcysteine (3.3%) decreased biofilm biomass and killed bacteria within the biofilms of E. coli isolates. The CFU of recoverable P. aeruginosa and K. pneumoniae isolates were decreased, but the biofilm biomass was unchanged. Exposure to hydrogen peroxide (1%) decreased the biofilm biomass and reduced the CFU of E. coli isolates, K. pneumoniae isolates were observed to have a reduction in CFU, and minimal effects were observed for P. aeruginosa isolates. Chelating agents (EDTA formulations) reduced E. coli CFU but were ineffective at disrupting preformed biofilms or decreasing the CFU of P. aeruginosa and K. pneumoniae within a biofilm. No single nonantibiotic treatment commonly used in equine veterinary practice was able to reduce the CFU and biofilm biomass of all three Gram-negative species of bacteria evaluated. An in vivo equine model of infectious endometritis was also developed to monitor biofilm formation, utilizing bioluminescence imaging with equine P. aeruginosa isolates from this study. Following infection, the endometrial surface contained focal areas of bacterial growth encased in a strongly adherent "biofilm-like" matrix, suggesting that biofilms are present during clinical cases of infectious equine endometritis. Our results indicate that Gram-negative bacteria isolated from the equine uterus are capable of producing a biofilm in vitro, and P. aeruginosa is capable of producing biofilm-like material in vivo. Bacterial endometritis is an important cause of subfertility in mares (1). Endometrial infections are reported in 25 to 60% of mares who fail to become pregnant following breeding (1), contributing to a major economic loss for the equine industry (1, 2). The most common species of bacteria identified during the clinical diagnosis of bacterial endometritis include Streptococcus equi subsp. zooepidemicus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa (3, 4). The isolation of one of these species of bacteria is considered to be clinically relevant due to observed reductions in pregnancy rates after identification (2). The detection of these bacteria in the uterus would result in treatment with uterine lavage and broad-spectrum antibiotics to reduce bacterial load and eradicate the remaining bacteria (5, 6).Bacterial endometritis that is refractory to traditional antimicrobial treatment is a significant challenge in the equine breeding industry (4). One possible explanation often cited for the failure of antibiotic treatment is the growth of bacterial pathogens in a biofilm (1, 5). Uterine isolates of E. coli, P. aeruginosa, and K. pneumoniae have been proposed to most likely be associated with a biofilm, due to the observation of repeated antibiotic treatment failures in equine reproducti...

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Alterations in Outer Membrane Permeability

Cited by 558 publications

References 31 publications

Recognition of Pathogenic Microbes by the Drosophila Phagocytic Pattern Recognition Receptor Eater

Recognition of Pathogenic Microbes by the Drosophila Phagocytic Pattern Recognition Receptor Eater

A PhoPQ-Regulated ABC Transporter System Exports Tetracycline in Pseudomonas aeruginosa

In Vitro Efficacy of Nonantibiotic Treatments on Biofilm Disruption of Gram-Negative Pathogens and an In Vivo Model of Infectious Endometritis Utilizing Isolates from the Equine Uterus

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