scholarly journals Gram-negative trimeric porins have specific LPS binding sites that are essential for porin biogenesis

2016 ◽  
Vol 113 (34) ◽  
pp. E5034-E5043 ◽  
Author(s):  
Wanatchaporn Arunmanee ◽  
Monisha Pathania ◽  
Alexandra S. Solovyova ◽  
Anton P. Le Brun ◽  
Helen Ridley ◽  
...  
Keyword(s):  
Binding Sites ◽  
Calcium Ion ◽  
Gram Negative Bacteria ◽  
Core Oligosaccharide ◽  
Gram Negative ◽  
X Ray ◽  
Cross Links ◽  
Phosphate Groups ◽  
Positively Charged ◽  
Lps Binding

The outer membrane (OM) of gram-negative bacteria is an unusual asymmetric bilayer with an external monolayer of lipopolysaccharide (LPS) and an inner layer of phospholipids. The LPS layer is rigid and stabilized by divalent cation cross-links between phosphate groups on the core oligosaccharide regions. This means that the OM is robust and highly impermeable to toxins and antibiotics. During their biogenesis, OM proteins (OMPs), which function as transporters and receptors, must integrate into this ordered monolayer while preserving its impermeability. Here we reveal the specific interactions between the trimeric porins of Enterobacteriaceae and LPS. Isolated porins form complexes with variable numbers of LPS molecules, which are stabilized by calcium ions. In earlier studies, two high-affinity sites were predicted to contain groups of positively charged side chains. Mutation of these residues led to the loss of LPS binding and, in one site, also prevented trimerization of the porin, explaining the previously observed effect of LPS mutants on porin folding. The high-resolution X-ray crystal structure of a trimeric porin–LPS complex not only helps to explain the mutagenesis results but also reveals more complex, subtle porin–LPS interactions and a bridging calcium ion.

scholarly journals Glucosamine Found as a Substituent of Both Phosphate Groups in Bordetella Lipid A Backbones: Role of a BvgAS-Activated ArnT Ortholog

2008 ◽  
Vol 190 (12) ◽  
pp. 4281-4290 ◽  
Author(s):  
Nico Marr ◽  
Alina Tirsoaga ◽  
Didier Blanot ◽  
Rachel Fernandez ◽  
Martine Caroff
Keyword(s):  
Lipid A ◽  
Biological Activities ◽  
Antigenic Determinants ◽  
Gram Negative Bacteria ◽  
Core Oligosaccharide ◽  
Gene Encoding ◽  
Gram Negative ◽  
Host Immune Responses ◽  
Covalently Linked ◽  
Phosphate Groups

ABSTRACT Endotoxins are amphipathic lipopolysaccharides (LPSs), major constituents of the outer membrane of gram-negative bacteria. They consist of a lipid region, covalently linked to a core oligosaccharide, to which may be linked a repetitive glycosidic chain carrying antigenic determinants. Most of the biological activities of endotoxins have been associated with the lipid moiety of the molecule: unique to gram-negative bacteria, LPS is a ligand of the mammalian TLR4-MD2-CD14 pathogen recognition receptor complex. Lipid A preparations are often heterogeneous with respect to both the numbers and the lengths of fatty acids and the natures of substituents on the phosphate groups when present. The variants can significantly affect host immune responses. Nine species in the Bordetella genus have been described, and the fine LPS structures of seven of them have been published. In this report, lipids A from Bordetella pertussis Tohama I and B. bronchiseptica strain 4650 were further characterized and revealed to have a glucosamine substituting both lipid A phosphate groups of the diglucosamine backbone. These substitutions have not been previously described for bordetellae. Moreover, a B. pertussis transposon mutation that maps within a gene encoding a Bordetella ArnT (formerly PmrK) glycosyl transferase ortholog does not carry this substitution, thus providing a genetic basis for the modification. Reverse transcriptase PCR of this locus showed that it is Bvg regulated, suggesting that the ability of Bordetella to modify lipid A via this glucosamine modification is a potential virulence trait.

scholarly journals Rational Design of Ag/ZnO Hybrid Nanoparticles on Sericin/Agarose Composite Film for Enhanced Antimicrobial Applications

2020 ◽  
Vol 22 (1) ◽  
pp. 105
Author(s):  
Wanting Li ◽  
Zixuan Huang ◽  
Rui Cai ◽  
Wan Yang ◽  
Huawei He ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Antimicrobial Activity ◽  
Composite Film ◽  
Water Absorption ◽  
Rational Design ◽  
Hybrid Nanoparticles ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
X Ray

Silver-based hybrid nanomaterials are receiving increasing attention as potential alternatives for traditional antimicrobial agents. Here, we proposed a simple and eco-friendly strategy to efficiently assemble zinc oxide nanoparticles (ZnO) and silver nanoparticles (AgNPs) on sericin-agarose composite film to impart superior antimicrobial activity. Based on a layer-by-layer self-assembly strategy, AgNPs and ZnO were immobilized on sericin-agarose films using the adhesion property of polydopamine. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray powder diffraction spectroscopy were used to show the morphology of AgNPs and ZnO on the surface of the composite film and analyze the composition and structure of AgNPs and ZnO, respectively. Water contact angle, swelling ratio, and mechanical property were determined to characterize the hydrophilicity, water absorption ability, and mechanical properties of the composite films. In addition, the antibacterial activity of the composite film was evaluated against Gram-positive and Gram-negative bacteria. The results showed that the composite film not only has desirable hydrophilicity, high water absorption ability, and favorable mechanical properties but also exhibits excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria. It has shown great potential as a novel antimicrobial biomaterial for wound dressing, artificial skin, and tissue engineering.

Synthesis and Characterization of Cadmium with Titanium Oxide (Cd-TiO2) Nanocomposite: Testing its Antibacterial Effect

2021 ◽  
Vol 12 (4) ◽  
pp. 2523-2529
Author(s):  
Daniel Sam N ◽  
Anish C I ◽  
Sabeena G ◽  
Rajaduraipandian S ◽  
Manobala ◽  
...  
Keyword(s):  
Sol Gel ◽  
Gram Negative Bacteria ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Gram Negative ◽  
X Ray ◽  
Weight Percentage ◽  
Inhibition Concentration ◽  
Xrd Patterns

Sol gel methods were used for the study of the antimicrobial activity of Cd-TiO2 against gram-negative and positive bacteria. These Cd-TiO2 have been characterized by various optical and techniques. They have been exhibited by X-ray diffraction, scanning electron microscopy, ultraviolet spectroscopy, and infrared spectroscopy. The structures of the various XRD patterns indicate that the product has a structure. The particle size of Cd-TiO2 is 35nm. The SEM images confirm the spherical appearance of the sample. The energy X-ray spectra have been confirmed as well and then C, O, Ti, Cd, Pt element are present in Cd-TiO2. The weight percentage of Cadmium is 5.8%, Ti is 51.03%, C is 5.13% and O is 31.75% in Cd-TiO2. BET image shows that the major pore size distribution of Cd-TiO2 is ranged from 2.24 nm. The Cd-TiO2 that the antibacterial activity when tested against the pathogens only gram-negative bacteria such as Pseudomonas. The zone of minimum inhibition concentration was measured in a range of 20mm in 25μl and 30mm in 100μl.

ANTIMICROBIAL ACTIVITY OF COPPER KAOLINITE AND SURFACTANT MODIFIED COPPER KAOLINITE AGAINST GRAM POSITIVE AND GRAM NEGATIVE BACTERIA

2016 ◽  
Vol 78 (3-2) ◽  
Author(s):  
Nor Syafawani Sarah Md Saad ◽  
Nik Ahmad Nizam Nik Malek ◽  
Chun Shiong Chong
Keyword(s):  
Antimicrobial Activity ◽  
Synergistic Effects ◽  
Wide Spectrum ◽  
Copper Nitrate ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
X Ray ◽  
Gram Positive Bacteria ◽  
Diffusion Technique

The aim of this research was to determine the antimicrobial activity of kaolinite modified with antimicrobial compounds against Gram positive and Gram negative bacteria. Copper kaolinite (Cu-kaolinite) was prepared by loading raw kaolinite with copper nitrate trihydrate (CuNO3) while surfactant modified Cu-kaolinite (SM-Cu-kaolinite) was prepared by adding cationic surfactants hexadecyltrimethyl ammonium (HDTMA) on Cu-Kaolinite. Samples was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyzer. The antimicrobial activity of the samples was tested against Gram negative bacteria (Escherichia coli ATCC 11229 and Pseudomonas aeruginosa ATCC 15442), and Gram positive bacteria (Staphylococcus aureus ATCC 6538 and Enterococcus faecalis ATCC 29212) through disc diffusion technique (DDT) and minimum inhibition concentration (MIC). The results showed that the antimicrobial activity of Cu-kaolinite increased after modified with HDTMA due to the synergistic effects of Cu ions and HDTMA molecules on the kaolinite. The antimicrobial activity for surfactant modified Cu-kaolinite was greater for Gram positive bacteria compared to Gram negative bacteria. In conclusion, the attachment of HDTMA on Cu-kaolinite contributed to the enhanced antimicrobial activity against wide spectrum of bacteria (Gram positive and Gram negative bacteria).

Mannich Reaction Product of Quinolin-8-ol (Oxine) and its Antibacterial Activity

1997 ◽  
Vol 50 (8) ◽  
pp. 861 ◽  
Author(s):  
Shaheen Faizi ◽  
Bina Shaheen Siddiqui ◽  
Rubeena Saleem ◽  
Farzana Akhtar ◽  
Khursheed Ali Khan ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Single Crystal ◽  
Mannich Reaction ◽  
Gram Negative Bacteria ◽  
X Ray Diffraction ◽  
Gram Positive ◽  
Gram Negative ◽  
Antimicrobial Screening ◽  
X Ray

Quinolin-8-ol (1) on reaction with 2,6-dichloroaniline and m-nitrobenzaldehyde afforded 7-(α-hydroxy- m-nitrobenzyl)quinolin-8-ol (2), which is an unusual Mannich reaction product. The structure of (2) was determined by spectroscopic and single-crystal X-ray diffraction studies. Preliminary antimicrobial screening showed that (1) and (2) have activity against a large number of Gram-positive and Gram-negative bacteria.

scholarly journals Essential Metal Uptake in Gram-negative Bacteria: X-ray Fluorescence, Radioisotopes, and Cell Fractionation

10.3791/57169 ◽  
2018 ◽  
Author(s):  
Christopher D. Radka ◽  
Lauren L. Radford ◽  
Adriana V.F. Massicano ◽  
Lawrence J. DeLucas ◽  
Suzanne E. Lapi ◽  
...  
Keyword(s):  
Metal Uptake ◽  
Gram Negative Bacteria ◽  
Cell Fractionation ◽  
Gram Negative ◽  
Essential Metal ◽  
X Ray

Nitric Oxide Inhibitory Activity of Xanthones from the Green Fruits of Cratoxylum formosum ssp. pruniflorum

2010 ◽  
Vol 63 (11) ◽  
pp. 1550 ◽  
Author(s):  
Nawong Boonnak ◽  
Achjana Khamthip ◽  
Chatchanok Karalai ◽  
Suchada Chantrapromma ◽  
Chanita Ponglimanont ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Antibacterial Activity ◽  
Inhibitory Activity ◽  
Spectroscopic Methods ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ic50 Values ◽  
Mic Value

Three new xanthones, pruniflorone M-O (1–3), and a new xanthonolignoid, 3-methoxy-5′-demethoxycadensin G (4), were isolated from the green fruits of Cratoxylum formosum ssp. pruniflorum along with three known xanthones (5–7) and a known flavonoid (8). Their structures were elucidated by spectroscopic methods and the structure of 1 was also determined by X-ray crystallography. Compounds 2 and 7 showed potent nitric oxide inhibitory activity with IC50 values of 4.4 and 4.3 μM, respectively. Moreover, 7 also showed strong antibacterial activity against both Gram-positive and Gram-negative bacteria with an MIC value of 4.67 μg mL–1.

scholarly journals Complete Lipooligosaccharide Structure from Pseudoalteromonas nigrifaciens Sq02-Rifr and Study of Its Immunomodulatory Activity

Marine Drugs ◽  
2021 ◽  
Vol 19 (11) ◽  
pp. 646
Author(s):  
Rossella Di Guida ◽  
Angela Casillo ◽  
Antonietta Stellavato ◽  
Celeste Di Meo ◽  
Soichiro Kawai ◽  
...  
Keyword(s):  
Chemical Structure ◽  
Lipid A ◽  
Membrane Integrity ◽  
Immunomodulatory Activity ◽  
Gram Negative Bacteria ◽  
Core Oligosaccharide ◽  
Gram Negative ◽  
Seriola Quinqueradiata ◽  
Specific Polysaccharide

Lipopolysaccharides (LPS) are surface glycoconjugates embedded in the external leaflet of the outer membrane (OM) of the Gram-negative bacteria. They consist of three regions: lipid A, core oligosaccharide (OS), and O-specific polysaccharide or O-antigen. Lipid A is the glycolipid endotoxin domain that anchors the LPS molecule to the OM, and therefore, its chemical structure is crucial in the maintenance of membrane integrity in the Gram-negative bacteria. In this paper, we reported the characterization of the lipid A and OS structures from Pseudoalteromonas nigrifaciens Sq02-Rifr, which is a psychrotrophic Gram-negative bacterium isolated from the intestine of Seriola quinqueradiata. The immunomodulatory activity of both LPS and lipid A was also examined.

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