Electron microscopic observations of polysaccharide components in polymyxin B treated outer membranes from Serratia marcescens.

Weber, Douglas A.; Nadakavukaren, Mathew J.; Tsang, J. C.

doi:10.7164/antibiotics.32.66

J. Antibiot.

1979

DOI: 10.7164/antibiotics.32.66

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Electron microscopic observations of polysaccharide components in polymyxin B treated outer membranes from Serratia marcescens.

Douglas A. Weber

Mathew J. Nadakavukaren

J. C. Tsang³

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Cited by 4 publications

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“…Because of the well-described morphological effects of polymyxin B on the outer membrane of S. marcescens, (11,12) thin-section transmission EM was employed to compare ultrastructural changes imposed by bis-LLP1 and polymyxin B. Equimolar peptide concentrations corresponding to the MBC at which 50% of strains tested are killed (MBC 50 ) for the index strain were used (Fig. 1).…”

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confidence: 99%

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

Phadke

Lazarevic²,

Bahr³

et al. 2002

Antimicrob Agents Chemother

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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.Vertebrate-derived antimicrobial peptides have been recognized as important components of the innate immune response (4). Appreciation of their biological activities has enabled their development as anti-infective agents (3). Possible mechanisms of membrane disruption have been proposed to involve outer membrane perturbation, breakdown of the cytoplasmic membrane, or interaction with cytoplasmic targets (13).The lentivirus lytic peptides (LLPs), encoded by discrete C-terminal sequences of the human immunodeficiency virus type 1 transmembrane protein, demonstrate potent antimicrobial activity (9), even though they have not evolved specifically for host defense against bacterial infection. While the antimicrobial activity of the LLPs is similar to that of other cationic antimicrobial peptides (CAPs) (10), there has been no investigation of its molecular basis of activity. This study compared the mechanisms of action of bis-LLP1, a dimerized and amidated LLP1 derivative, and polymyxin B against S. marcescens by using a standard in vitro broth dilution assay followed by electron microscopy (EM) and biochemical analysis.The potencies of bis-LLP1 and polymyxin B for S. marcescens were compared on a molar basis ( Fig. 1) with a standard broth dilution assay (8) and found to be equivalent (minimal bactericidal concentration [MBC], 1 M). Polymyxin B consistently demonstrated a biphasic curve with an inflection between 1 and 10 M, which was not typical of most antimicrobial peptides. Complete sterilization of a bacterial broth culture was achieved at concentrations greater than 10 M for polymyxin B, possibly resulting from its organization into micelles. The relevant finding from this experiment was that bis-LLP1 and polymyxin B showed equivalent MBCs against S. marcescens.Both bis-LLP1 and polymyxin B have been proposed to act via bacterial membrane perturbation. Because of the well-described morphological effects of polymyxin B on the outer membrane of S. marcescens, (11, 12) thin-section transmission EM was employed to compare ultrastructural changes imposed by bis-LLP1 and polymyxin B. Equimolar peptide concentrations corresponding to the MBC at which 50% of strains tested are killed (MBC 50 ) for the index strain were used (Fig. 1). These concentrations were used because at higher concentrations bacterial structures could not be pelleted. Treatment of S. marcescens with bis-LLP1 at its In this assay, 10 6 CFU of bacteria per ml in phosphate buffer were exposed to increasing concentrations of peptides for 1 h. Viable bacteria were diluted and spread onto plates, followed ...

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mentioning

confidence: 99%

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

Phadke

Lazarevic²,

Bahr³

et al. 2002

Antimicrob Agents Chemother

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Phomoxanthones A and B, Novel Xanthone Dimers from the Endophytic Fungus Phomopsis Species

et al. 2001

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The History of Colistin Resistance Mechanisms in Bacteria: Progress and Challenges

2021

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Since 2015, the discovery of colistin resistance genes has been limited to the characterization of new mobile colistin resistance (mcr) gene variants. However, given the complexity of the mechanisms involved, there are many colistin-resistant bacterial strains whose mechanism remains unknown and whose exploitation requires complementary technologies. In this review, through the history of colistin, we underline the methods used over the last decades, both old and recent, to facilitate the discovery of the main colistin resistance mechanisms and how new technological approaches may help to improve the rapid and efficient exploration of new target genes. To accomplish this, a systematic search was carried out via PubMed and Google Scholar on published data concerning polymyxin resistance from 1950 to 2020 using terms most related to colistin. This review first explores the history of the discovery of the mechanisms of action and resistance to colistin, based on the technologies deployed. Then we focus on the most advanced technologies used, such as MALDI-TOF-MS, high throughput sequencing or the genetic toolbox. Finally, we outline promising new approaches, such as omics tools and CRISPR-Cas9, as well as the challenges they face. Much has been achieved since the discovery of polymyxins, through several innovative technologies. Nevertheless, colistin resistance mechanisms remains very complex.

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Electron microscopic observations of polysaccharide components in polymyxin B treated outer membranes from Serratia marcescens.

Cited by 4 publications

References 18 publications

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

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

Phomoxanthones A and B, Novel Xanthone Dimers from the Endophytic Fungus Phomopsis Species

The History of Colistin Resistance Mechanisms in Bacteria: Progress and Challenges

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