Interaction of silver doped carbon nanotubes-cyclodextrin nanocomposites with Escherichia coli bacteria during water purification

Silver doped multi-walled carbon nanotube/β-cyclodextrin (1% Ag-MWCNTs/β-CD) nanocomposite was prepared by reductive pre-treatment of Ag+ on MWCNTs, followed by binding with β-CD. Crystalline structure, morphology and crystallite size estimation were carried out by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The interaction between Escherichia coli (E. coli), ATCC 25922 bacteria and 1% Ag doped MWCNTs/β-CD nanocomposite was investigated by FE-SEM. The antibacterial activity of the nanocomposite was studied by monitoring the absorbance of contaminated water using a UV-vis spectrophotometer. The nanocomposites caused a growth delay in the growth rate of E. coli bacteria. The structural analysis of the bacteria by FE-SEM showed clusters of nanocomposite anchored to the bacterial cell wall during the initial stages of interaction. Results also indicate that treated bacteria show significant damage on the outer membranes, which were recognised by the formation of ‘pits’. The study shows that 1% Ag-MWCNTs/β-CD nanocomposite is bactericidal.

Download Full-text

Extraction and characterisation of cellulose nanocrystals (CNCs) from sugarcane bagasse using ionic liquids

10.51415/10321/3219 ◽

2019 ◽

Author(s):

◽

Gcinile Pretty Mdletshe

Keyword(s):

Electron Microscopy ◽

Ionic Liquids ◽

Sugarcane Bagasse ◽

Cellulose Nanocrystals ◽

Crystallinity Index ◽

Attenuated Total Reflection ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Pre Treatment

Lignocellulosic materials have the potential to partly replace fossil-based resources as a source of bio-fuels, bio-chemicals, bio-composites and other bio-products. In this study, ionic liquids (ILs) were used in the pre-treatment of ground sugarcane bagasse (SCB). The ILs used were 1-butyl-3-methylimidazolium hydrogen sulphate or 1-butyl-3-methylimidazolium methyl sulphate at varied times. The ILs were able to remove lignin and hemicellulose from biomass. The IL [bmim][HSO4] had the highest amount of lignin removed after 12 h than all samples. Moreover, it resulted in the greatest cellulose amount. Milled SCB was pre-treated with IL/dimethyl sulphoxide (DMSO) mixtures. The IL [bmim][HSO4] was able to produce cellulose nanocrystals (CNCs) at 90 % IL and 100 % IL. The other IL failed to produce CNCs. Freeze drying the CNC suspension showed morphologies of long fibrous structures and rods which were evident in the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The crystallinity index of cellulose in the form of CNCs was calculated from powder X-ray diffraction (P-XRD). Thermal analysis of the CNCs was obtained from thermogravimetric analysis (TGA). Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to confirm the absence of lignin and hemicellulose in CNCs. The size distribution of CNCs was obtained by using a dynamic light scattering (DLS) which showed that all the CNCs for the 100 % IL [bmim][HSO4] pre-treatment had a length < 500 nm. It was found that [bmim][HSO4], with no DMSO, was the most effective in terms of cellulose dissolution and the crystal sizes of CNCs. The conversion of cellulose to CNCs was successful with a 80 % and 100 % conversion for 90 % [bmim][HSO4]/DMSO and 100 % [bmim][HSO4], respectively.

Download Full-text

Screening of Condensed Tannins from Canadian Prairie Forages for Anti–Escherichia coli O157:H7 with an Emphasis on Purple Prairie Clover (Dalea purpurea Vent)†

Journal of Food Protection ◽

10.4315/0362-028x.jfp-12-259 ◽

2013 ◽

Vol 76 (4) ◽

pp. 560-567 ◽

Cited By ~ 22

Author(s):

Y. WANG ◽

L. JIN ◽

K. H. OMINSKI ◽

M. HE ◽

Z. XU ◽

...

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Transmission Electron Microscopy ◽

Condensed Tannins ◽

Brown Seaweed ◽

Coli Strain ◽

Escherichia Coli O157 ◽

Canadian Prairie ◽

E Coli ◽

Transmission Electron

Tannins from forages grown (n = 10) on the Canadian prairie, as well as from Quebracho, Rhus semialata, and brown seaweed (Ascophyllum nodosum), were screened for anti–Escherichia coli O157:H7 activity against E. coli O157:H7 strain 3081 at a concentration of 400 μg/ml for each tannin type, except for brown seaweed, which was at 50 μg/ml. Growth of the bacteria was assessed by measuring the optical density at 600 nm over 24 h. Tannin from seaweed at a concentration of 50 μg/ml inhibited growth of strain 3081. Among the terrestrial forages, only condensed tannins (CT) from purple prairie clover (Dalea purpurea Vent; PPC) increased (P < 0.05) the lag time and reduced (P < 0.05) the growth rate of E. coli O157:H7. The anti–E. coli O157:H7 activity of PPC CT was further assessed by culturing E. coli strain ATCC 25922 and eight strains of E. coli O157:H7 with PPC CT at 0, 25, 50, 100, or 200 μg/ml. Selected strains were enumerated after 0, 6, and 24 h of incubation, and fatty acid composition was determined after 24 h of incubation. E. coli strain 25922 was cultured with 0, 50, or 200 μg of CT per ml and harvested during the exponential growth phase for examination by transmission electron microscopy. Increasing CT concentration linearly increased (P < 0.001) the lag times of seven strains and linearly reduced (P < 0.001) the growth rates of eight E. coli O157:H7 strains. Proportions of unsaturated fatty acids in the total fatty acids were decreased (P < 0.01) by CT at 50 μg/ml. Transmission electron microscopy showed that CT disrupted the outer membrane structure. Anti–E. coli O157:H7 activity of PPC CT at levels of up to 200 μg/ml was bacteriostatic rather than bactericidal, and the mechanism of anti–E. coli activity may involve alteration in the fatty acid composition and disruption of the outer membrane of the cell.

Download Full-text

Nd@TiO2 Nanocomposite for Photocatalytic Inactivation of Escherichia coli

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2020.16951 ◽

2020 ◽

Vol 20 (3) ◽

pp. 1447-1453 ◽

Cited By ~ 1

Author(s):

De-Shuai Zhen ◽

Xiao-Hu Luo ◽

De Yang ◽

Hong-Tao Zou ◽

Er-Hu Xiong ◽

...

Keyword(s):

Escherichia Coli ◽

Diffuse Reflectance Spectroscopy ◽

Anatase Phase ◽

Sol Gel ◽

High Specific Surface Area ◽

X Ray Diffraction ◽

E Coli ◽

Simulated Solar Light ◽

Solar Light Irradiation ◽

Transmission Electron

In present work, a novel Nd@TiO2 Nanocomposite, synthesized successfully by a facile sol–gel method, reveals significant light-activated antibacterial activity. The X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) show the anatase phase and globular shape of Nd@TiO2. UV-vis diffuse reflectance spectroscopy and low temperature N2 adsorption (BET) indicate Nd0.02@TiO2 has the narrow band gap (3.0 eV) and a high specific surface area (121.1 m2·g-1). Furthermore, the prepared Nd@TiO2 exhibits unprecedented higher photocatalytic activity than P25 TiO2. In water, Nd@TiO2 has higher inactivation against Escherichia coli (E. coli) bacteria under simulated solar light irradiation 70 min than TiO2, and the highest antibacterial efficiency (91.5%) of E. coli was achieved on Nd0.02@TiO2.

Download Full-text

Comparison in Gnotobiotic Pigs of Lesions Caused by Verotoxigenic and Non-verotoxigenic Escherichia coli

Veterinary Pathology ◽

10.1177/030098588802500304 ◽

1988 ◽

Vol 25 (3) ◽

pp. 205-210 ◽

Cited By ~ 12

Author(s):

G. A. Hall ◽

N. Chanter ◽

A. P. Bland

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Transmission Electron Microscopy ◽

Intestinal Tissue ◽

E Coli ◽

Histological Sections ◽

Transmission Electron ◽

Colony Forming Units ◽

Gnotobiotic Pigs

To compare the pathogenesis of calf and rabbit strains of E. coli. gnotobiotic pigs were infected with 1010 colony forming units (cfu) of verotoxigenic strain RDEC-1 or S102-9, or a non-verotoxigenic E. coli (X114/83). Pigs were killed 4 days later, and intestinal tissue was fixed and examined by light, scanning, and transmission electron microscopy. Strains S102-9 and RDEC-1 caused diarrhea, attached to enterocytes, and effaced microvilli, confirming that the calf and rabbit strains possessed similar mechanisms of pathogenicity. Non-verotoxigenic strain X114/83 did not cause diarrhea, but in 5/5 piglets it was detected in histological sections adherent to enterocyte surfaces. Exfoliated enterocytes were seen in 4/5. Bacteria attached to enterocytes by “cups” and “pedestals,” with effacement of microvilli, were seen by electron microscopy in 1/5 piglets. It was concluded that strain S102-9 appears to be an animal equivalent of human enterohemorrhagic E. coli. that verotoxin is not essential in the pathogenesis of attaching and effacing lesions, and that the lesions induced by S102-9 are more severe in gnotobiotic pigs than in gnotobiotic or conventional calves.

Download Full-text

Structure-Function Relationship of Antibacterial Synthetic Peptides Homologous to a Helical Surface Region on Human Lactoferrin against Escherichia coli Serotype O111

Infection and Immunity ◽

10.1128/iai.66.6.2434-2440.1998 ◽

1998 ◽

Vol 66 (6) ◽

pp. 2434-2440 ◽

Cited By ~ 72

Author(s):

Daniel S. Chapple ◽

David J. Mason ◽

Christopher L. Joannou ◽

Edward W. Odell ◽

Vanya Gant ◽

...

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Transmission Electron Microscopy ◽

Flow Cytometry ◽

Antibacterial Activity ◽

Synthetic Peptides ◽

Membrane Integrity ◽

E Coli ◽

Transmission Electron ◽

Helical Region

ABSTRACT Lactoferricin includes an 11-amino-acid amphipathic alpha-helical region which is exhibited on the outer surface of the amino-terminal lobe of lactoferrin. Synthetic peptides homologous to this region exhibited potent antibacterial activity against a selected range of both gram-negative and gram-positive bacteria. An analog synthesized with methionine substituted for proline at position 26, which is predicted to disrupt the helical region, abolished antibacterial activity against Escherichia coli and considerably reduced antibacterial activity against Staphylococcus aureus and anAcinetobacter strain. The mode of action of human lactoferrin peptide (HLP) 2 against E. coli serotype O111 (NCTC 8007) was established by using flow cytometry, surface plasmon resonance, and transmission electron microscopy. Flow cytometry was used to monitor membrane potential, membrane integrity, and metabolic processes by using the fluorescent probes bis-1,3-(dibutylbarbituric acid)-trimethine oxonol, propidium iodide, and carbonyl cyanide m-chlorophenylhydrazone, respectively. HLP 2 was found to act at the cell membrane, causing complete loss of membrane potential after 10 min and of membrane integrity within 30 min, with irreversible damage to the cell as shown by rapid loss of viability. The number of particles, measured by light scatter on the flow cytometer, dropped significantly, showing that bacterial lysis resulted. The peptide was shown to bind toE. coli O111 lipopolysaccharide by using surface plasmon resonance. Transmission electron microscopy revealed bacterial distortion, with the outer membrane becoming detached from the inner cytoplasmic membrane. We conclude that HLP 2 causes membrane disruption of the outer membrane, resulting in lysis, and that structural considerations are important for antibacterial activity.

Download Full-text

Antibacterial Mechanism of Catfish Bone Hydrolysate Revealed by Atomic Force and Transmission Electron Microscopy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.554-556.1346 ◽

2012 ◽

Vol 554-556 ◽

pp. 1346-1349

Author(s):

Xiao Qing Ren ◽

Peng Liang ◽

Li Zhen Ma ◽

Hong Shun Yang

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Bacterial Membrane ◽

Antibacterial Mechanism ◽

E Coli ◽

Atomic Force ◽

Transmission Electron ◽

Bacterial Cell Membrane ◽

Volume Decrease ◽

Coli Growth

The aim of this study was to investigate the effect of the catfish bone hydrolysate (CBH) on morphology of bacteria which were observed by atomic force microscope (AFM) and transmission electron microscope (TEM). The CBH was found to inhibit Escherichia coli (E. coli) growth. The CBH at 10 mg/ml caused the significant fragmentariness in the bacterial membrane and a severe volume decrease. A possible mechanism is that CBH damages the structure of bacterial cell membrane which causes E. coli bacteria to die eventually.

Download Full-text

Effect of Slightly Acidic Electrolyzed Water for Inactivating Escherichia coli O157:H7 and Staphylococcus aureus Analyzed by Transmission Electron Microscopy

Journal of Food Protection ◽

10.4315/0362-028x-73.12.2211 ◽

2010 ◽

Vol 73 (12) ◽

pp. 2211-2216 ◽

Cited By ~ 39

Author(s):

SONGJIAN NAN ◽

YONGYU LI ◽

BAOMING LI ◽

CHAOYUAN WANG ◽

XIAODONG CUI ◽

...

Keyword(s):

Electron Microscopy ◽

Escherichia Coli ◽

Staphylococcus Aureus ◽

Transmission Electron Microscopy ◽

Treatment Time ◽

Escherichia Coli O157 ◽

Electrolyzed Water ◽

E Coli ◽

Transmission Electron ◽

And Staphylococcus Aureus

The use of different available chlorine concentrations (ACCs) of slightly acidic electrolyzed water (SAEW; 0.5 to 30 mg/liter), different treatment times, and different temperatures for inactivating Escherichia coli O157:H7 and Staphylococcus aureus was evaluated. The morphology of both pathogens also was analyzed with transmission electron microscopy. A 3-min treatment with SAEW (pH 6.0 to 6.5) at ACCs of 2 mg/liter for E. coli O157:H7 and 8 mg/liter for S. aureus resulted in 100% inactivation of two cultures (7.92- to 8.75-log reduction) at 25°C. The bactericidal activity of SAEW was independent of the treatment time and temperature at a higher ACC (P > 0.05). E. coli O157:H7 was much more sensitive than S. aureus to SAEW. The morphological damage to E. coli O157:H7 cells by SAEW was significantly greater than that to S. aureus cells. At an ACC as high as 30 mg/liter, E. coli O157:H7 cells were damaged, but S. aureus cells retained their structure and no cell wall damage or shrinkage was observed. SAEW with a near neutral pH may be a promising disinfectant for inactivation of foodborne pathogens.

Download Full-text

Controlling the Antimicrobial Action of Surface Modified Magnesium Hydroxide Nanoparticles

Biomimetics ◽

10.3390/biomimetics4020041 ◽

2019 ◽

Vol 4 (2) ◽

pp. 41 ◽

Cited By ~ 10

Author(s):

Ahmed F. Halbus ◽

Tommy S. Horozov ◽

Vesselin N. Paunov

Keyword(s):

Electron Microscopy ◽

Antimicrobial Activity ◽

Magnesium Hydroxide ◽

Inorganic Nanoparticles ◽

X Ray Diffraction ◽

X Ray ◽

E Coli ◽

Transmission Electron ◽

Surface Modified ◽

Magnesium Hydroxide Nanoparticles

Magnesium hydroxide nanoparticles (Mg(OH)2NPs) have recently attracted significant attention due to their wide applications as environmentally friendly antimicrobial nanomaterials, with potentially low toxicity and low fabrication cost. Here, we describe the synthesis and characterisation of a range of surface modified Mg(OH)2NPs, including particle size distribution, crystallite size, zeta potential, isoelectric point, X-ray diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). We explored the antimicrobial activity of the modified Mg(OH)2NPs on the microalgae (C. reinhardtii), yeast (S. cerevisiae) and Escherichia coli (E. coli). The viability of these cells was evaluated for various concentrations and exposure times with Mg(OH)2NPs. It was discovered that the antimicrobial activity of the uncoated Mg(OH)2NPs on the viability of C. reinhardtii occurred at considerably lower particle concentrations than for S. cerevisiae and E. coli. Our results indicate that the antimicrobial activity of polyelectrolyte-coated Mg(OH)2NPs alternates with their surface charge. The anionic nanoparticles (Mg(OH)2NPs/PSS) have much lower antibacterial activity than the cationic ones (Mg(OH)2NPs/PSS/PAH and uncoated Mg(OH)2NPs). These findings could be explained by the lower adhesion of the Mg(OH)2NPs/PSS to the cell wall, because of electrostatic repulsion and the enhanced particle-cell adhesion due to electrostatic attraction in the case of cationic Mg(OH)2NPs. The results can be potentially applied to control the cytotoxicity and the antimicrobial activity of other inorganic nanoparticles.

Download Full-text

Synthesis and Antibacterial Aspects of Graphitic C3N4@Polyaniline Composites

Coatings ◽

10.3390/coatings10100950 ◽

2020 ◽

Vol 10 (10) ◽

pp. 950

Author(s):

Mohammad Oves ◽

Mohammad Omaish Ansari ◽

Reem Darwesh ◽

Afzal Hussian ◽

Mohamed F. Alajmi ◽

...

Keyword(s):

Electron Microscopy ◽

Morphological Analysis ◽

Oxidative Polymerization ◽

X Ray Diffraction ◽

X Ray ◽

E Coli ◽

Transmission Electron ◽

Aging Conditions ◽

Polyaniline Composites

In this work, Pani and Pani@g-C3N4 was synthesized by in situ oxidative polymerization methodology of aniline, in the presence of g-C3N4. The as prepared Pani@g-C3N4 was characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction (XRD). The morphological analysis showed well dispersed Pani in g-C3N4, as well as the coating of Pani on g-C3N4. The XRD further revealed this, and peaks of Pani as well as g-C3N4 was observed, thereby suggesting successful synthesis of the composite. The DC electrical conductivity studies under isothermal and cyclic aging conditions showed high stability of composites over 100 °C. Further, the synthesized composite material proved to be an excellent antimicrobial agent against both type i.e., gram positive Streptococcus pneumoniae and negative bacteria Escherichia coli. In the zone inhibition assay 18 ± 0.5, 16 ± 0.75 and 20 ± 0.5, 22 ± 0.5 mm zone diameter were found against E. coli and S. pneumoniae in presence of pure g-C3N4 and Pani@g-C3N4 at 50 µg concentrations, respectively. Further antimicrobial activity in the presence of sunlight in aqueous medium showed that Pani@g-C3N4 is more potent than pure g-C3N4.

Download Full-text

Cerium doped hydroxyapatite nanoparticles synthesized by coprecipitation method

Journal of the Serbian Chemical Society ◽

10.2298/jsc150824007c ◽

2016 ◽

Vol 81 (4) ◽

pp. 433-446 ◽

Cited By ~ 16

Author(s):

Carmen Ciobanu ◽

Cristina Popa ◽

Daniela Predoi

Keyword(s):

Electron Microscopy ◽

Progressive Increase ◽

Morphological Properties ◽

Bacterial Strains ◽

X Ray Diffraction ◽

X Ray ◽

E Coli ◽

Transmission Electron ◽

Ft Raman Spectroscopy ◽

Xrd Studies

The present work reports a simple coprecipitation adapted method for the synthesis of stable Ce substituted to Ca hydroxyapatite (HAp) nanoparticles. The structural and morphological properties of Ce doped hydroxyapatite (Ce:HAp) were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDAX). The optical properties of Ce doped hydroxyapatite were also investigated using Fourier Transform Infrared (FTIR) spectroscopy, FT Raman spectroscopy and photoluminescence analysis. The results of the XRD studies revealed the progressive increase in the a- and c-axes with increasing of Ce concentrations. In the FTIR studies of Ce:HAp powders a similar structure to hydroxyapatite was observed. IR and Raman wavenumbers and the peak strength of the bands associated to the P-O and O-H bonds decreases progressively with the increase of Ce concentration. All the emission maxima could be attributed to the 5d-4f transitions of Ce ions. The displacement of maximum emission bands with the increase of Cerium in the samples is in agreement with the results obtained by XRD studies. The Ce:HAp samples with xCe =0.03 and 0.05 exhibited significant antibacterial activity against Staphylococcus aureus ATCC 6538 and E. coli 714 bacterial strains compared to Ce:HAp samples with xCe =0 (pure HAp) and 0.01.

Download Full-text