scholarly journals Endotoxin protein: a B-cell mitogen and polyclonal activator of C3H/HeJ lymphocytes.

1976 ◽  
Vol 144 (3) ◽  
pp. 821-827 ◽  
Author(s):  
B M Sultzer ◽  
G W Goodman
Keyword(s):  
B Cell ◽  
Lipid A ◽  
Protein A ◽  
Cell Wall Protein ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Lipopolysaccharide Endotoxin ◽  
Polyclonal Activator ◽  
A Cell ◽  
Cell Mitogen

A cell wall protein that is ordinarily complexed to the lipopolysaccharide endotoxin in gram-negative bacteria has been separated by the use of aqueous phenol. The protein is active as a B-cell mitogen and polyclonal activator of murine lymphocytes including the C3H/HeJ strain which is a nonresponder to lipoplysaccharide or lipid A.

scholarly journals Binding of surfactant protein A to the lipid A moiety of bacterial lipopolysaccharides

1994 ◽  
Vol 303 (2) ◽  
pp. 407-411 ◽  
Author(s):  
J F Van Iwaarden ◽  
J C Pikaar ◽  
J Storm ◽  
E Brouwer ◽  
J Verhoef ◽  
...  
Keyword(s):  
Lipid A ◽  
Magnetic Beads ◽  
Protein A ◽  
Surfactant Protein ◽  
Biologically Active ◽  
Surfactant Protein A ◽  
Carbohydrate Binding ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli

Surfactant protein A (SP-A) enhances the phagocytosis of opsonized and non-opsonized bacteria by alveolar macrophages, but it is not known with which component of the bacterial surface it associates. We investigated the interaction of SP-A with lipopolysaccharides (LPS), which are important biologically active constituents of the outer membranes of Gram-negative bacteria. Flow cytometry was used to study the binding of fluorescein isothiocyanate-labelled SP-A either to LPS of various chain lengths coupled to magnetic beads or to Gram-negative bacteria. The binding of SP-A to LPS-coated beads was saturable, both time- and concentration-dependent, and required both Ca2+ and Na+. SP-A bound to the lipid A moiety of LPS and to LPS from either the Re-mutant of Salmonella minnesota or the J5-mutant of Escherichia coli. In contrast, it did not bind to O111 LPS of E. coli, suggesting that SP-A binds only to rough LPS. The binding of SP-A to LPS was not affected by mannan and heparin or by deglycosylation of the SP-A, indicating that the carbohydrate-binding domain and the carbohydrate moiety of SP-A are not involved in its interaction with LPS. We also observed saturable and concentration-dependent binding of SP-A to the live J5 mutant of whole E. coli, but not to its O111 mutant. In addition, Re LPS aggregated in the presence of SP-A, Ca2+ and Na+. We conclude that SP-A associates with LPS via the lipid A moiety of rough LPS and may be involved in the anti-bacterial defences of the lung.

scholarly journals Direct detection of lipid A on intact Gram-negative bacteria by MALDI-TOF mass spectrometry

2016 ◽  
Vol 120 ◽  
pp. 68-71 ◽  
Author(s):  
Gerald Larrouy-Maumus ◽  
Abigail Clements ◽  
Alain Filloux ◽  
Ronan R. McCarthy ◽  
Serge Mostowy
Keyword(s):  
Mass Spectrometry ◽  
Lipid A ◽  
Direct Detection ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Maldi Tof Mass Spectrometry ◽  
Maldi Tof

scholarly journals In situ identification of Gram-negative bacteria in human lungs using a topical fluorescent peptide targeting lipid A

2018 ◽  
Vol 10 (464) ◽  
pp. eaal0033 ◽  
Author(s):  
Ahsan R. Akram ◽  
Sunay V. Chankeshwara ◽  
Emma Scholefield ◽  
Tashfeen Aslam ◽  
Neil McDonald ◽  
...  
Keyword(s):  
Lipid A ◽  
Respiratory Infections ◽  
Bacterial Species ◽  
Water Soluble ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Human Lungs ◽  
Fluorescent Peptide ◽  
Bacterial Lipid

Respiratory infections in mechanically ventilated patients caused by Gram-negative bacteria are a major cause of morbidity. Rapid and unequivocal determination of the presence, localization, and abundance of bacteria is critical for positive resolution of the infections and could be used for patient stratification and for monitoring treatment efficacy. Here, we developed an in situ approach to visualize Gram-negative bacterial species and cellular infiltrates in distal human lungs in real time. We used optical endomicroscopy to visualize a water-soluble optical imaging probe based on the antimicrobial peptide polymyxin conjugated to an environmentally sensitive fluorophore. The probe was chemically stable and nontoxic and, after in-human intrapulmonary microdosing, enabled the specific detection of Gram-negative bacteria in distal human airways and alveoli within minutes. The results suggest that pulmonary molecular imaging using a topically administered fluorescent probe targeting bacterial lipid A is safe and practical, enabling rapid in situ identification of Gram-negative bacteria in humans.

Diacylglycerol kinase A is essential for polymyxin resistance provided by EptA, MCR-1 and other lipid A phosphoethanolamine transferases.

2021 ◽  
Author(s):  
Alexandria B. Purcell ◽  
Bradley J. Voss ◽  
M. Stephen Trent
Keyword(s):  
Lipid A ◽  
Cell Envelope ◽  
Diacylglycerol Kinase ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli ◽  
Severe Reduction ◽  
Bacterial Fitness ◽  
Phosphoethanolamine Transferases ◽  
Kinase A

Gram-negative bacteria utilize glycerophospholipids (GPLs) as phospho-form donors to modify various surface structures. These modifications play important roles in bacterial fitness in diverse environments influencing cell motility, recognition by the host during infection, and antimicrobial resistance. A well-known example is the modification of the lipid A component of lipopolysaccharide by the phosphoethanolamine (pEtN) transferase EptA that utilizes phosphatidyethanoalmine (PE) as the phospho-form donor. Addition of pEtN to lipid A promotes resistance to cationic antimicrobial peptides (CAMPs), including the polymyxin antibiotics like colistin. A consequence of pEtN modification is the production of diacylglycerol (DAG) that must be recycled back into GPL synthesis via the diacylglycerol kinase A (DgkA). DgkA phosphorylates DAG forming phosphatidic acid, the precursor for GPL synthesis. Here we report that deletion of dgkA in polymyxin-resistant E. coli results in a severe reduction of pEtN modification and loss of antibiotic resistance. We demonstrate that inhibition of EptA is regulated post-transcriptionally and is not due to EptA degradation during DAG accumulation. We also show that the inhibition of lipid A modification by DAG is a conserved feature of different Gram-negative pEtN transferases. Altogether, our data suggests that inhibition of EptA activity during DAG accumulation likely prevents disruption of GPL synthesis helping to maintain cell envelope homeostasis.

Select Gram-negative Aerobic Bacteria

2012 ◽  
pp. 90-101
Author(s):  
David R. McNamara ◽  
Franklin R. Cockerill
Keyword(s):  
Cell Wall ◽  
Sepsis Syndrome ◽  
Vital Role ◽  
Klebsiella Pneumonia ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Neisseria Meningitides ◽  
A Cell ◽  
Normal Human ◽  
Specific Species

Gram-negative bacteria may be rod-shaped (bacilli), spherical (cocci), oval, helical, or filamentous. Cytoplasmic membrane is surrounded by a cell wall consisting of a peptidoglycan layer and an outer cell membrane. Gram-negative bacteria are widely distributed in the natural environment. They are commensals with many animals and play a vital role in normal human physiology as intestinal commensals. Gram-negative bacteria are the cause of various human illnesses. The gram-negative bacterial cell wall contains various lipopolysaccharide endotoxins. Endotoxins trigger intense inflammation and the sepsis syndrome during infection. Specific species of gram-negative bacteria such as Neisseria meningitides, Moraxella catarrhalis, Acinetobacter, Vibrio, Klebsiella pneumonia, Salmonella, Pseudomonas aeruginosa, and Haemophilus influenza are reviewed.

scholarly journals Outer Membrane Lipid Secretion and the Innate Immune Response to Gram-Negative Bacteria

2020 ◽  
Vol 88 (7) ◽  
Author(s):  
Nicole P. Giordano ◽  
Melina B. Cian ◽  
Zachary D. Dalebroux
Keyword(s):  
Outer Membrane ◽  
Mammalian Cells ◽  
Lipid A ◽  
Membrane Lipid ◽  
Membrane Curvature ◽  
Host Immunity ◽  
Host Recognition ◽  
Permeability Barrier ◽  
Gram Negative Bacteria ◽  
Gram Negative

ABSTRACT The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer that consists of inner leaflet phospholipids and outer leaflet lipopolysaccharides (LPS). The asymmetric character and unique biochemistry of LPS molecules contribute to the OM’s ability to function as a molecular permeability barrier that protects the bacterium against hazards in the environment. Assembly and regulation of the OM have been extensively studied for understanding mechanisms of antibiotic resistance and bacterial defense against host immunity; however, there is little knowledge on how Gram-negative bacteria release their OMs into their environment to manipulate their hosts. Discoveries in bacterial lipid trafficking, OM lipid homeostasis, and host recognition of microbial patterns have shed new light on how microbes secrete OM vesicles (OMVs) to influence inflammation, cell death, and disease pathogenesis. Pathogens release OMVs that contain phospholipids, like cardiolipins, and components of LPS molecules, like lipid A endotoxins. These multiacylated lipid amphiphiles are molecular patterns that are differentially detected by host receptors like the Toll-like receptor 4/myeloid differentiation factor 2 complex (TLR4/MD-2), mouse caspase-11, and human caspases 4 and 5. We discuss how lipid ligands on OMVs engage these pattern recognition receptors on the membranes and in the cytosol of mammalian cells. We then detail how bacteria regulate OM lipid asymmetry, negative membrane curvature, and the phospholipid-to-LPS ratio to control OMV formation. The goal is to highlight intersections between OM lipid regulation and host immunity and to provide working models for how bacterial lipids influence vesicle formation.

Functional analysis of the lysis genes of Staphylococcus aureus phage P68 in Escherichia coli

Microbiology ◽  
2005 ◽  
Vol 151 (7) ◽  
pp. 2331-2342 ◽  
Author(s):  
Marian Takáč ◽  
Angela Witte ◽  
Udo Bläsi
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Functional Analysis ◽  
Transmembrane Domains ◽  
Class I ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Reading Frame ◽  
Double Stranded Dna ◽  
A Cell

Double-stranded DNA phages of both Gram-positive and Gram-negative bacteria typically use a holin–endolysin system to achieve lysis of their host. In this study, the lysis genes of Staphylococcus aureus phage P68 were characterized. P68 gene lys16 was shown to encode a cell-wall-degrading enzyme, which causes cell lysis when externally added to clinical isolates of S. aureus. Another gene, hol15, was identified embedded in the −1 reading frame at the 3′ end of lys16. The deduced Hol15 protein has three putative transmembrane domains, and thus resembles class I holins. An additional candidate holin gene, hol12, was found downstream of the endolysin gene lys16 based on two predicted transmembrane domains of the encoded protein, which is a typical trait of class II holins. The synthesis of either Hol12 or Hol15 resulted in growth retardation of Escherichia coli, and both hol15 and hol12 were able to complement a phage λ Sam mutation. The hol15 gene has a dual start motif beginning with the codons Met1-Lys2-Met3…. Evidence is presented that the hol15 gene encodes a lysis inhibitor (anti-holin) and a lysis effector (actual holin). As depolarization of the membrane converted the anti-holin to a functional holin, these studies suggested that hol15 functions as a typical dual start motif class I holin. The unusual arrangement of the P68 lysis genes is discussed.

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