scholarly journals Linearized esculentin-2EM shows pH dependent antibacterial activity with an alkaline optimum

2021 ◽  
Author(s):  
Erum Malik ◽  
David A. Phoenix ◽  
Timothy J. Snape ◽  
Frederick Harris ◽  
Jaipaul Singh ◽  
...  
Keyword(s):  
Helical Structure ◽  
Food Preservation ◽  
Forming Process ◽  
Gram Positive ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria ◽  
Alkaline Conditions ◽  
Ph Dependent ◽  
Gram Negative Organisms

AbstractHere the hypothesis that linearized esculentin 2EM (E2EM-lin) from Glandirana emeljanovi possesses pH dependent activity is investigated. The peptide showed weak activity against Gram-negative bacteria (MLCs ≥ 75.0 μM) but potent efficacy towards Gram-positive bacteria (MLCs ≤ 6.25 μM). E2EM-lin adopted an α-helical structure in the presence of bacterial membranes that increased as pH was increased from 6 to 8 (↑ 15.5–26.9%), whilst similar increases in pH enhanced the ability of the peptide to penetrate (↑ 2.3–5.1 mN m−1) and lyse (↑ 15.1–32.5%) these membranes. Theoretical analysis predicted that this membranolytic mechanism involved a tilted segment, that increased along the α-helical long axis of E2EM-lin (1–23) in the N → C direction, with −  < µH > increasing overall from circa − 0.8 to − 0.3. In combination, these data showed that E2EM-lin killed bacteria via novel mechanisms that were enhanced by alkaline conditions and involved the formation of tilted and membranolytic, α-helical structure. The preference of E2EM-lin for Gram-positive bacteria over Gram-negative organisms was primarily driven by the superior ability of phosphatidylglycerol to induce α-helical structure in the peptide as compared to phosphatidylethanolamine. These data were used to generate a novel pore-forming model for the membranolytic activity of E2EM-lin, which would appear to be the first, major reported instance of pH dependent AMPs with alkaline optima using tilted structure to drive a pore-forming process. It is proposed that E2EM-lin has the potential for development to serve purposes ranging from therapeutic usage, such as chronic wound disinfection, to food preservation by killing food spoilage organisms.

Fusobacterium nucleatum, the first Gram-negative bacterium demonstrated to produce polyglutamate

2009 ◽  
Vol 55 (5) ◽  
pp. 627-632 ◽  
Author(s):  
Thomas Candela ◽  
Marie Moya ◽  
Michel Haustant ◽  
Agnès Fouet
Keyword(s):  
In Silico Analysis ◽  
Fusobacterium Nucleatum ◽  
Gram Negative Bacteria ◽  
Negative Bacterium ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
The Third ◽  
Gram Negative Organisms ◽  
First Time

Poly-γ-glutamate has been described in many Gram-positive organisms. When anchored to the surface, it is a capsule and as such a virulence factor. Based on sequence similarities, few Gram-negative organisms have been suggested to synthesize poly-γ-glutamate. For the first time, a Gram-negative bacterium, Fusobacterium nucleatum , is shown to produce and secrete poly-γ-glutamate. Putative poly-γ-glutamate-synthesizing genes from Gram-negative organisms have been compared with their Gram-positive homologs by in silico analysis, i.e., gene sequence and phylogenetic analysis. Clusters of three instead of four genes were highlighted by our screen. The products of the first two genes display similarity with their Gram-positive equivalents, yet the sequences from the Gram-negative organisms can be distinguished from those of the Gram-positives. Interestingly, the sequence of the predicted product of the third gene is conserved among Gram-negative bacteria but displays no similarity to that of either the third or fourth gene of the Gram-positive operons. It is suggested that, like for Gram-positive bacteria, poly-γ-glutamate has a role in virulence for pathogens and one in survival for other Gram-negative bacteria.

scholarly journals Secretory Phospholipase A2 Is the Principal Bactericide for Staphylococci and Other Gram-Positive Bacteria in Human Tears

1998 ◽  
Vol 66 (6) ◽  
pp. 2791-2797 ◽  
Author(s):  
Xiao-Dan Qu ◽  
Robert I. Lehrer
Keyword(s):  
Bactericidal Activity ◽  
Tear Film ◽  
Phospholipase A ◽  
Secretory Phospholipase A2 ◽  
Gram Positive ◽  
Gram Negative ◽  
Secretory Phospholipase ◽  
Calcium Dependent ◽  
Gram Positive Bacteria ◽  
Gram Negative Organisms

ABSTRACT We examined human tears for molecules that killed gram-positive bacteria. The principal mediator of bactericidal activity against staphylococci proved to be a calcium-dependent enzyme, secretory phospholipase A2. Whereas the concentration of secretory phospholipase A2 in the normal tear film exceeded 30 μg/ml, only 1.1 ng (<0.1 nM) of the enzyme per ml sufficed to killListeria monocytogenes and 15 to 80 ng/ml killedStaphylococcus aureus. Despite its efficacy against gram-positive bacteria, secretory phospholipase A2 lacked bactericidal activity against gram-negative organisms (Escherichia coli, Salmonella typhimurium, andPseudomonas aeruginosa) when tested in the ionic environment of tears. Given the presence of secretory phospholipase A2 in tears, intestinal secretions, and leukocytes, this enzyme may play a substantial role in innate mucosal and systemic bactericidal defenses against gram-positive bacteria.

scholarly journals Effects of Antibacterial Peptide F1 on Bacterial Liposome Membrane Integrity

2021 ◽  
Vol 8 ◽  
Author(s):  
Qun Wang ◽  
Bo Peng ◽  
Mingyue Song ◽  
Abdullah ◽  
Jun Li ◽  
...  
Keyword(s):  
Antimicrobial Peptide ◽  
Membrane Structure ◽  
Bacterial Membrane ◽  
Phospholipid Membranes ◽  
Phospholipid Membrane ◽  
Gram Positive ◽  
Liposome Membrane ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria

Previous studies from our lab have shown that the antimicrobial peptide F1 obtained from the milk fermentation by Lactobacillus paracasei FX-6 derived from Tibetan kefir was different from common antimicrobial peptides; specifically, F1 simultaneously inhibited the growth of Gram-negative and Gram-positive bacteria. Here, we present follow-on work demonstrating that after the antimicrobial peptide F1 acts on either Escherichia coli ATCC 25922 (E. coli) or Staphylococcus aureus ATCC 63589 (S. aureus), their respective bacterial membranes were severely deformed. This deformation allowed leakage of potassium and magnesium ions from the bacterial membrane. The interaction between the antimicrobial peptide F1 and the bacterial membrane was further explored by artificially simulating the bacterial phospholipid membranes and then extracting them. The study results indicated that after the antimicrobial peptide F1 interacted with the bacterial membranes caused significant calcein leakage that had been simulated by different liposomes. Furthermore, transmission electron microscopy observations revealed that the phospholipid membrane structure was destroyed and the liposomes presented aggregation and precipitation. Quartz Crystal Microbalance with Dissipation (QCM-D) results showed that the antimicrobial peptide F1 significantly reduced the quality of liposome membrane and increased their viscoelasticity. Based on the study's findings, the phospholipid membrane particle size was significantly increased, indicating that the antimicrobial peptide F1 had a direct effect on the phospholipid membrane. Conclusively, the antimicrobial peptide F1 destroyed the membrane structure of both Gram-negative and Gram-positive bacteria by destroying the shared components of their respective phospholipid membranes which resulted in leakage of cell contents and subsequently cell death.

scholarly journals Identification of the Lyso-Form N-Acyl Intramolecular Transferase in Low-GC Firmicutes

2017 ◽  
Vol 199 (11) ◽  
Author(s):  
Krista M. Armbruster ◽  
Timothy C. Meredith
Keyword(s):  
Fatty Acid ◽  
Cell Envelope ◽  
Transmembrane Protein ◽  
Physiological Role ◽  
Gram Positive ◽  
Gram Negative ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Unknown Gene ◽  
Gram Negative Organisms

ABSTRACT Bacterial lipoproteins are embedded in the cell membrane of both Gram-positive and Gram-negative bacteria, where they serve numerous functions central to cell envelope physiology. Lipoproteins are tethered to the membrane by an N-acyl-S-(mono/di)-acyl-glyceryl-cysteine anchor that is variously acylated depending on the genus. In several low-GC, Gram-positive firmicutes, a monoacyl-glyceryl-cysteine with an N-terminal fatty acid (known as the lyso form) has been reported, though how it is formed is unknown. Here, through an intergenic complementation rescue assay in Escherichia coli, we report the identification of a common orthologous transmembrane protein in both Enterococcus faecalis and Bacillus cereus that is capable of forming lyso-form lipoproteins. When deleted from the native host, lipoproteins remain diacylated with a free N terminus, as maturation to the N-acylated lyso form is abolished. Evidence is presented suggesting that the previously unknown gene product functions through a novel intramolecular transacylation mechanism, transferring a fatty acid from the diacylglycerol moiety to the α-amino group of the lipidated cysteine. As such, the discovered gene has been named lipoprotein intramolecular transacylase (lit), to differentiate it from the gene for the intermolecular N-acyltransferase (lnt) involved in triacyl lipoprotein biosynthesis in Gram-negative organisms. IMPORTANCE This study identifies a new enzyme, conserved among low-GC, Gram-positive bacteria, that is involved in bacterial lipoprotein biosynthesis and synthesizes lyso-form lipoproteins. Its discovery is an essential first step in determining the physiological role of N-terminal lipoprotein acylation in Gram-positive bacteria and how these modifications impact bacterial cell envelope function.

Distinct antibacterial activity of a vertically aligned graphene coating against Gram-positive and Gram-negative bacteria

2020 ◽  
Vol 8 (28) ◽  
pp. 6069-6079
Author(s):  
Wei Wei ◽  
Jiurong Li ◽  
Zeyang Liu ◽  
Yuan Deng ◽  
Da Chen ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Gram Negative Bacteria ◽  
Antibacterial Mechanism ◽  
Si Substrate ◽  
Gram Positive ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria ◽  
Graphene Coating ◽  
Vertically Aligned

The distinct antibacterial mechanism of vertical graphene Si toward bacteria. Vertical graphene kills Gram-positive bacteria through physical disruption and Si substrate kills Gram-negative bacteria by extracting electrons from bacterial membranes.

scholarly journals PAMAM-dendrimer Enhanced Antibacterial Effect of Vancomycin Hydrochloride Against Gram-Negative Bacteria

2018 ◽  
Vol 22 ◽  
pp. 10-21 ◽  
Author(s):  
Azadeh Serri ◽  
Arash Mahboubi ◽  
Afshin Zarghi ◽  
Hamid Reza Moghimi
Keyword(s):  
Antibacterial Activity ◽  
Inhibitory Concentration ◽  
In Vitro Release ◽  
Pamam Dendrimers ◽  
Dilution Method ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria

Purpose: The antibacterial activity of some antibiotics is specific to either Gram-positive or Gram-negative bacteria.  There are different mechanisms behind such insensitivities like inability of antibiotics to permeate through some bacterial membranes, as is the case for vancomycin in Gram-negative bacteria. The present investigation tries to overcome this problem by dendrimers, in order to make Gram-negative bacteria responsive to vancomycin. Methods: The effects of generations 3 (G3) and 5 (G5) polyamidoamine amine-terminated dendrimers (NH2-PAMAM), on the antibacterial activity of vancomycin, were evaluated. Vancomycin-PAMAM dendrimers complexes were prepared and their antibacterial activities were evaluated by determination of their “minimum inhibitory concentration (MIC)”, “minimum bactericidal concentration” and “fractional inhibitory concentration index” values against two Gram-positive and four Gram-negative bacteria, using broth micro-dilution method. The complexation of vancomycin and dendrimers was also assessed by in vitro release studies across dialysis tubing using a developed HPLC method. Results: Results showed that vancomycin solution was effective against Gram-positive bacteria, but, was not effective in Gram-negative ones. Vancomycin-PAMAM dendrimers exhibited significant antibacterial efficacy against Gram-negative bacteria resulting in a decline of vancomycin MIC values by about 2, 2, 4 and 64 times in E. coli, K. pneumonia, S. typhimurium and P. aeruginosa, respectively. Results also showed that enhanced effect by G5 is more than G3. Dendrimers did not affect antibacterial activity of vancomycin in Gram-positive bacteria, as no permeation problem exists here. Conclusions: The present study revealed that both G3 and G5 cationic PAMAM dendrimers are able to make Gram-negative bacteria sensitive to vancomycin, resulting in decline of MIC values up to 64 times, possibly by increasing its permeation through bacterial membrane. These results look promising for broadening the antibacterial spectrum of vancomycin and such a strategy might be used for increasing the overall life of antibiotics.

scholarly journals Stapled Anoplin as an Antibacterial Agent

2021 ◽  
Vol 12 ◽  
Author(s):  
Monika Wojciechowska ◽  
Julia Macyszyn ◽  
Joanna Miszkiewicz ◽  
Renata Grzela ◽  
Joanna Trylska
Keyword(s):  
Antimicrobial Activity ◽  
Helical Structure ◽  
Eukaryotic Cells ◽  
Helical Conformation ◽  
Iodide Uptake ◽  
Gram Positive ◽  
Amphipathic Peptide ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Α Helix

Anoplin is a linear 10-amino acid amphipathic peptide (Gly-Leu-Leu-Lys-Arg-Ile-Lys-Thr-Leu-Leu-NH2) derived from the venom sac of the solitary wasp. It has broad antimicrobial activity, including an antibacterial one. However, the inhibition of bacterial growth requires several dozen micromolar concentrations of this peptide. Anoplin is positively charged and directly interacts with anionic biological membranes forming an α-helix that disrupts the lipid bilayer. To improve the bactericidal properties of anoplin by stabilizing its helical structure, we designed and synthesized its analogs with hydrocarbon staples. The staple was introduced at two locations resulting in different charges and amphipathicity of the analogs. Circular dichroism studies showed that all modified anoplins adopted an α-helical conformation, both in the buffer and in the presence of membrane mimics. As the helicity of the stapled anoplins increased, their stability in trypsin solution improved. Using the propidium iodide uptake assay in Escherichia coli and Staphylococcus aureus, we confirmed the bacterial membrane disruption by the stapled anoplins. Next, we tested the antimicrobial activity of peptides on a range of Gram-negative and Gram-positive bacteria. Finally, we evaluated peptide hemolytic activity on sheep erythrocytes and cytotoxicity on human embryonic kidney 293 cells. All analogs showed higher antimicrobial activity than unmodified anoplin. Depending on the position of the staple, the peptides were more effective either against Gram-negative or Gram-positive bacteria. Anoplin[5-9], with a lower positive charge and increased hydrophobicity, had higher activity against Gram-positive bacteria but also showed hemolytic and destructive effects on eukaryotic cells. Contrary, anoplin[2-6] with a similar charge and amphipathicity as natural anoplin effectively killed Gram-negative bacteria, also pathogenic drug-resistant strains, without being hemolytic and toxic to eukaryotic cells. Our results showed that anoplin charge, amphipathicity, and location of hydrophobic residues affect the peptide destructive activity on the cell wall, and thus, its antibacterial activity. This means that by manipulating the charge and position of the staple in the sequence, one can manipulate the antimicrobial activity.

scholarly journals The antibiotic negamycin crosses the bacterial cytoplasmic membrane by multiple routes

2021 ◽  
Author(s):  
Daniel Hörömpöli ◽  
Catherine Ciglia ◽  
Karl-Heinz Glüsenkamp ◽  
Lars Ole Haustedt ◽  
Hildegard Falkenstein-Paul ◽  
...  
Keyword(s):  
Cytoplasmic Membrane ◽  
Binding Mode ◽  
Blood Levels ◽  
Gram Positive ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Target Interaction ◽  
Gram Positive Bacteria ◽  
Multiple Routes ◽  
Resistance Rates

Negamycin is a natural pseudo-dipeptide antibiotic with promising activity against Gram-negative and Gram-positive bacteria, including Enterobacteriaceae, Pseudomonas aeruginosa, and Staphylococcus aureus, and good efficacy in infection models. It binds to ribosomes with a novel binding mode, stimulating miscoding and inhibiting ribosome translocation. We were particularly interested in studying how the small, positively charged natural product reaches its cytoplasmic target in Escherichia coli. Negamycin crosses the cytoplasmic membrane by multiple routes depending on environmental conditions. In a peptide-free medium, negamycin uses endogenous peptide transporters for active translocation, preferentially the dipeptide permease Dpp. However, in the absence of functional Dpp or in the presence of outcompeting nutrient peptides, negamycin can still enter the cytoplasm. We observed a contribution of the DppA homologs SapA and OppA, as well as of DtpD, a proton-dependent oligopeptide transporter. Calcium strongly improves the activity of negamycin against both Gram-negative and Gram-positive bacteria, especially at concentrations around 2.5 mM, reflecting human blood levels. Calcium forms a complex with negamycin and facilitates its interaction with negatively charged phospholipids in bacterial membranes. Moreover, decreased activity at acidic pH and under anaerobic conditions point to a role of the membrane potential in negamycin uptake. Accordingly, improved activity at alkaline pH could be linked to increased uptake of [3H]negamycin. The diversity of options for membrane translocation is reflected by low resistance rates. The example of negamycin demonstrates that membrane passage of antibiotics can be multi-faceted and that for cytoplasmic anti-Gram-negative drugs, understanding of permeation and target interaction are equally important.

scholarly journals In vitro evaluation of ABT-719, a novel DNA gyrase inhibitor.

1995 ◽  
Vol 39 (4) ◽  
pp. 964-970 ◽  
Author(s):  
R K Flamm ◽  
C Vojtko ◽  
D T Chu ◽  
Q Li ◽  
J Beyer ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Active Compound ◽  
Dna Gyrase ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
New Class ◽  
Gram Negative Organisms ◽  
Gyrase Inhibitors

ABT-719 (A-86719.1) is the first compound of a new class of novel DNA gyrase inhibitors, the 2-pyridones, with potent antibacterial activity against gram-positive, gram-negative, and anaerobic organisms. ABT-719 was more active than ciprofloxacin, sparfloxacin, and clinafloxacin against gram-positive bacteria. ABT-719 was particularly active against Staphylococcus aureus (MIC at which 90% of the isolates were inhibited [MIC90] = 0.015 micrograms/ml) and Streptococcus pneumoniae (MIC90 = 0.03 micrograms/ml). ABT-719 was also the most active of the compounds tested against ciprofloxacin-resistant S. aureus isolates, with an MIC90 of 0.25 micrograms/ml, compared with 64 micrograms/ml for ciprofloxacin. Against gram-negative organisms, ABT-719 was as active as or slightly more active than ciprofloxacin and was the most active compound against ciprofloxacin-resistant Pseudomonas aeruginosa (MIC90 = 2.0 micrograms/ml). ABT-719 was also the most active compound against both gram-positive and gram-negative anaerobes, with MIC90s ranging from 0.12 to 0.25 micrograms/ml.

scholarly journals Ciprofloxacin, Lomefloxacin, or Levofloxacin as Treatment for Chronic Osteomyelitis

2000 ◽  
Vol 44 (1) ◽  
pp. 164-166 ◽  
Author(s):  
Richard N. Greenberg ◽  
Michael T. Newman ◽  
Saeed Shariaty ◽  
Richard W. Pectol
Keyword(s):  
Chronic Osteomyelitis ◽  
Average Duration ◽  
Effective Therapy ◽  
Efficacy And Safety ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
Duration Of Therapy ◽  
Gram Negative Organisms

ABSTRACT The efficacy and safety of three oral fluoroquinolones (lomefloxacin, levofloxacin, and ciprofloxacin) for the treatment of chronic osteomyelitis were analyzed. Twenty-seven patients had documented infections with quinolone-sensitive organisms and received either lomefloxacin, levofloxacin, or ciprofloxacin. Levofloxacin was effective therapy for 9 of 15 (60%) patients. Lomefloxacin was effective therapy for five of seven (71%) patients, and ciprofloxacin was effective therapy for two of five patients (40%). Average follow-up was 11.8 months for patients who completed the course of therapy, and the average duration of therapy was 60.6 days. Gram-positive bacteria were isolated from 18 patients, and 11 patients were cured. Oral fluoroquinolones can be safe, effective therapy if they are given for a prolonged course as treatment for infections caused by susceptible gram-positive as well as gram-negative organisms and in combination with adequate surgical debridement.

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