scholarly journals Comparison of Two Transmission Electron Microscopy Methods to Visualize Drug-Induced Alterations of Gram-Negative Bacterial Morphology

Antibiotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 307
Author(s):  
Hang Thi Nguyen ◽  
Lisa A. O’Donovan ◽  
Henrietta Venter ◽  
Cecilia C. Russell ◽  
Adam McCluskey ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Bacterial Cells ◽  
Drug Induced ◽  
Gram Negative ◽  
Transmission Electron ◽  
Bacterial Morphology ◽  
Clear Delineation ◽  
Bacterial Cell Membrane ◽  
Membrane Ultrastructure

In this study, we optimized and compared different transmission electron microscopy (TEM) methods to visualize changes to Gram-negative bacterial morphology induced by treatment with a robenidine analogue (NCL195) and colistin combination. Aldehyde-fixed bacterial cells (untreated, treated with colistin or NCL195 + colistin) were prepared using conventional TEM methods and compared with ultrathin Tokuyasu cryo-sections. The results of this study indicate superiority of ultrathin cryo-sections in visualizing the membrane ultrastructure of Escherichia coli and Pseudomonas aeruginosa, with a clear delineation of the outer and inner membrane as well as the peptidoglycan layer. We suggest that the use of ultrathin cryo-sectioning can be used to better visualize and understand drug interaction mechanisms on the bacterial cell membrane.

Molecular and atomic analysis of uranium complexes formed by three eco-types of Acidithiobacillus ferrooxidans

2002 ◽  
Vol 30 (4) ◽  
pp. 669-672 ◽  
Author(s):  
M. Merroun ◽  
C. Hennig ◽  
A. Rossberg ◽  
G. Geipel ◽  
T. Reich ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Acidithiobacillus Ferrooxidans ◽  
Energy Dispersive ◽  
Bacterial Cells ◽  
X Ray ◽  
Uranium Complexes ◽  
Transmission Electron ◽  
Polyphosphate Bodies ◽  
Atomic Analysis

A combination of EXAFS, transmission electron microscopy and energy-dispersive X-ray was used to conduct a molecular and atomic analysis of the uranium complexes formed by Acidithiobacillus ferrooxidans. The results demonstrate that this bacterium accumulates uranium as phosphate compounds. We suggest that at toxic levels when the uranium enters the bacterial cells, A. ferrooxidans can detoxify and efflux this metal by a process in which its polyphosphate bodies are involved.

Determination of Bacterial Cell Dry Mass by Transmission Electron Microscopy and Densitometric Image Analysis

1998 ◽  
Vol 64 (2) ◽  
pp. 688-694 ◽  
Author(s):  
M. Loferer-Krößbacher ◽  
J. Klima ◽  
R. Psenner
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Image Analysis ◽  
Bacterial Biomass ◽  
Dry Weight ◽  
Dry Mass ◽  
Bacterial Cells ◽  
E Coli ◽  
Transmission Electron ◽  
Bacterial Assemblages

ABSTRACT We applied transmission electron microscopy and densitometric image analysis to measure the cell volume (V) and dry weight (DW) of single bacterial cells. The system was applied to measure the DW ofEscherichia coli DSM 613 at different growth phases and of natural bacterial assemblages of two lakes, Piburger See and Gossenköllesee. We found a functional allometric relationship between DW (in femtograms) and V (in cubic micrometers) of bacteria (DW = 435 · V 0.86); i.e., smaller bacteria had a higher ratio of DW to V than larger cells. The measured DW of E. coli cells ranged from 83 to 1,172 fg, and V ranged from 0.1 to 3.5 μm3(n = 678). Bacterial cells from Piburger See and Gossenköllesee (n = 465) had DWs from 3 fg (V = 0.003 μm3) to 1,177 fg (V = 3.5 μm3). Between 40 and 50% of the cells had a DW of less than 20 fg. By assuming that carbon comprises 50% of the DW, the ratio of carbon content to Vof individual cells varied from 466 fg of C μm−3 forVs of 0.001 to 0.01 μm3 to 397 fg of C μm−3 (0.01 to 0.1 μm3) and 288 fg of C μm−3 (0.1 to 1 μm3). Exponentially growing and stationary cells of E. coli DSM 613 showed conversion factors of 254 fg of C μm−3 (0.1 to 1 μm3) and 211 fg of C μm−3 (1 to 4 μm3), respectively. Our data suggest that bacterial biomass in aquatic environments is higher and more variable than previously assumed from volume-based measurements.

Hexavalent chromium uptake by an Arthrobacter species: Electron microscope studies

1984 ◽  
Vol 42 ◽  
pp. 680-681
Author(s):  
R. Bhatnagar ◽  
R. N. Coleman
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Present Report ◽  
Bacterial Cells ◽  
Chromium Vi ◽  
Transmission Electron ◽  
Bacterial Removal ◽  
Scanning Transmission ◽  
Arthrobacter Species ◽  
Micro Organisms

Many micro-organisms are capable of taking up and accumulating specific metal ions from their environment. As a part of a study to evaluate bacterial removal of chromium from waste liquid streams, bacterial isolate (#96) identified as an Arthrobacter sp. was selected from 362 isolates and was reported to exhibit high tolerance to and uptake of chromium VI as determined by chemical methods.2 The present report describes fine structural studies of #96 with Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) to further understand the location of chromium accumulation and uptake. Attempts have been made to localize chromium on/in bacterial cells using Energy-Dispersive X-ray Microanalysis (EDX) and elemental mapping.

The Relationship Between Pit Membrane Ultrastructure and Chemical Impregnability of Wood

Holzforschung ◽  
1999 ◽  
Vol 53 (4) ◽  
pp. 341-346 ◽  
Author(s):  
Adya Singh ◽  
Bernard Dawson ◽  
Robert Franich ◽  
Faye Cowan ◽  
Jeremy Warnes
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Light Microscopy ◽  
Cell Types ◽  
Transmission Electron ◽  
Pit Membrane ◽  
Before And After ◽  
Ray Cells ◽  
Membrane Ultrastructure ◽  
The Relationship

Summary The woods of Alder and Eucalypt were examined by light microscopy before and after a chemical treatment by the Indurite process to increase the hardness of the wood. The pattern of wood cell impregnation for Alder differed significantly from Eucalypt in some respects. In Alder wood all cell types eg. vessels, fibres and rays, were impregnated in similar proportions. In comparison, in Eucalypt wood the impregnation material was largely confined to ray cells and the lumina of vessels; other cell types were either not impregnated or impregnated in very small numbers. Transmission electron microscopy of Alder and Eucalypt woods suggests that ultrastructural differences in the texture and porosity of pit membranes may be the main reason for the observed differences between these wood species with regard to their impregnability by the impregnation material used.

Repositioning rafoxanide to treat Gram-negative bacilli infections

2020 ◽  
Vol 75 (7) ◽  
pp. 1895-1905 ◽  
Author(s):  
Andrea Miró-Canturri ◽  
Rafael Ayerbe-Algaba ◽  
Ángel Rodríguez Villodres ◽  
Jerónimo Pachón ◽  
Younes Smani
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Morphological Changes ◽  
Gram Negative ◽  
Sepsis Model ◽  
Transmission Electron ◽  
Kill Curve ◽  
Time Kill

Abstract Objectives Repurposing drugs provides a new approach to the fight against MDR Gram-negative bacilli (MDR-GNB). Rafoxanide, a veterinary antihelminthic drug, has shown antibacterial activity in vitro against Gram-positive bacteria. We aimed to analyse the in vitro and in vivo efficacy of rafoxanide in combination with colistin against colistin-susceptible (Col-S) and colistin-resistant (Col-R) GNB. Methods A collection of Col-S and Col-R Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae were used. Chequerboard and time–kill curve analyses were performed to determine the synergy between rafoxanide and colistin. Changes in membrane structure and permeability were analysed using transmission electron microscopy and fluorescence assays. A murine peritoneal sepsis model using Col-R strains of these pathogens was performed to study the efficacy of rafoxanide (10 mg/kg/24 h, IV), colistimethate sodium (CMS) (20 mg/kg/8 h, intraperitoneally) and rafoxanide (10 mg/kg/24 h, IV) plus CMS (20 mg/kg/8 h, intraperitoneally) for 72 h. Results Rafoxanide showed MICs ≥256 mg/L for all Col-S and Col-R strains. Chequerboard and time–kill curve analyses showed that rafoxanide (1 mg/L) is more synergistic with colistin against Col-R than Col-S strains. Col-R, but not Col-S, strains treated with rafoxanide demonstrated higher membrane permeabilization. Transmission electron microscopy visualization confirmed that Col-R strains suffer morphological changes. In the murine peritoneal sepsis model with Col-R strains, rafoxanide plus CMS, compared with CMS alone, increased mouse survival to 53.8% and 73.3%, and reduced bacterial loads in tissues and blood between 2.34 and 4.99 log10 cfu/g or mL, respectively. Conclusions Rafoxanide repurposing, as monotherapy and in combination with CMS, may address the urgent need for new treatments for infections caused by MDR-GNB.

scholarly journals The Decoration of ZnO Nanoparticles by Gamma Aminobutyric Acid, Curcumin Derivative and Silver Nanoparticles: Synthesis, Characterization and Antibacterial Evaluation

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 442
Author(s):  
Chanon Talodthaisong ◽  
Kittiya Plaeyao ◽  
Chatariga Mongseetong ◽  
Wissuta Boonta ◽  
Oranee Srichaiyapol ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Silver Nanoparticles ◽  
Antibacterial Activities ◽  
Aminobutyric Acid ◽  
Gamma Aminobutyric Acid ◽  
Zno Nps ◽  
Gram Positive ◽  
Gram Negative ◽  
Transmission Electron

Zinc oxide nanoparticles (ZnO NPs) are applied in various applications in catalysis, biosensing, imaging, and as antibacterial agents. Here we prepared ZnO nanomaterials decorated by γ-aminobutyric acid (GABA), curcumin derivatives (CurBF2) and silver nanoparticles (CurBF2-AgNPs). The structures of all ZnO nanostructures were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV–VIS spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Further, their antibacterial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were investigated through analysis of minimum inhibitory concentration (MIC) method. Among the prepared nanostructures, the ZnO NPs-GABA/CurBF2-AgNPs showed excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. ZnO NPs fabricated here may have potential use in future anti-bacterial compositions and coatings technologies.

Development of bacterial biofilms in dairy processing lines

1995 ◽  
Vol 62 (3) ◽  
pp. 509-519 ◽  
Author(s):  
John W. Austin ◽  
Gilles Bergeron
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Amorphous Matrix ◽  
Raw Milk ◽  
Bacterial Biofilms ◽  
Bacterial Cells ◽  
Contact Sites ◽  
Dairy Processing ◽  
Transmission Electron ◽  
Scanning Electron

SummaryAdherence of bacteria to various milk contact sites was examined by scanning electron microscopy and transmission electron microscopy. New gaskets, endcaps, vacuum breaker plugs and pipeline inserts were installed in different areas in lines carrying either raw or pasteurized milk, and a routine schedule of cleaning-in-place and sanitizing was followed. Removed cleaned and sanitized gaskets were processed for scanning or transmission electron microscopy. Adherent bacteria were observed on the sides of gaskets removed from both pasteurized and raw milk lines. Some areas of Buna-n gaskets were colonized with a confluent layer of bacterial cells surrounded by an extensive amorphous matrix, while other areas of Buna-n gaskets showed a diffuse adherence over large areas of the surface. Most of the bacteria attached to polytetrafluoroethylene (PTFE or Teflon™) gaskets were found in crevices created by insertion of the gasket into the pipeline. Examination of stainless steel endcaps, pipeline inserts, and PTFE vacuum breaker plugs did not reveal the presence of adherent bacteria. The results of this study indicate that biofilms developed on the sides of gaskets in spite of cleaning-in-place procedures. These biofilms may be a source of post-pasteurization contamination.

scholarly journals New flat embedding method for transmission electron microscopy reveals an unknown mechanism of tetracycline

2019 ◽  
Author(s):  
Michaela Wenzel ◽  
Marien P. Dekker ◽  
Biwen Wang ◽  
Maroeska J. Burggraaf ◽  
Wilbert Bitter ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cell Membrane ◽  
Large Scale ◽  
Public Health Problem ◽  
Fixation Method ◽  
Bacterial Cells ◽  
Embedding Method ◽  
Transmission Electron ◽  
Flat Embedding

AbstractTransmission electron microscopy (TEM) is an important imaging technique in bacterial research and requires ultrathin sectioning of resin embedding of cell pellets. This method consumes milli- to deciliters of culture and results in sections of randomly orientated cells. For rod-shaped bacteria, this makes it exceedingly difficult to find longitudinally cut cells, which precludes large-scale quantification of morphological phenotypes. Here, we describe a new fixation method using either thin agarose layers or carbon-coated glass surfaces that enables flat embedding of bacteria. This technique allows for the observation of thousands of longitudinally cut rod-shaped cells per single section and requires only microliter culture volumes. We successfully applied this technique to Gram-positive Bacillus subtilis, Gram-negative Escherichia coli, the tuberculosis vaccine strain Mycobacterium bovis BCG, and the cell wall-lacking mycoplasma Acholeplasma laidlawii. To assess the potential of the technique to quantify morphological phenotypes, we examined cellular changes induced by a panel of different antibiotics. Surprisingly, we found that the ribosome inhibitor tetracycline causes significant deformations of the cell membrane. Further investigations showed that the presence of tetracycline in the cell membrane changes membrane organization and affects the peripheral membrane proteins MinD, MinC, and MreB, which are important for regulation of cell division and elongation. Importantly, we could show that this effect is not the result of ribosome inhibition but is a secondary antibacterial activity of tetracycline that has defied discovery for more than 50 years.SignificanceBacterial antibiotic resistance is a serious public health problem and novel antibiotics are urgently needed. Before a new antibiotic can be brought to the clinic, its antibacterial mechanism needs to be elucidated. Transmission electron microscopy is an important tool to investigate these mechanisms. We developed a flat embedding method that enables examination of many more bacterial cells than classical protocols, enabling large-scale quantification of phenotypic changes. Flat embedding can be adapted to most growth conditions and microbial species and can be employed in a wide variety of microbiological research fields. Using this technique, we show that even well-established antibiotics like tetracycline can have unknown additional antibacterial activities, demonstrating how flat embedding can contribute to finding new antibiotic mechanisms.

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