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.

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

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Michaela Wenzel ◽  
Marien P. Dekker ◽  
Biwen Wang ◽  
Maroeska J. Burggraaf ◽  
Wilbert Bitter ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Large Scale ◽  
Embedding Method ◽  
Peripheral Membrane Proteins ◽  
Transmission Electron ◽  
Cell Sample ◽  
Flat Embedding ◽  
Induced Changes ◽  
Membrane Deformations

AbstractTransmission electron microscopy of cell sample sections is a popular technique in microbiology. Currently, ultrathin sectioning is done on resin-embedded cell pellets, which consumes milli- to deciliters of culture and results in sections of randomly orientated cells. This is problematic for rod-shaped bacteria and often precludes large-scale quantification of morphological phenotypes due to the lack of sufficient numbers of longitudinally cut cells. Here we report a flat embedding method that enables observation of thousands of longitudinally cut cells per single section and only requires microliter culture volumes. We successfully applied this technique to Bacillus subtilis, Escherichia coli, Mycobacterium bovis, and Acholeplasma laidlawii. To assess the potential of the technique to quantify morphological phenotypes, we monitored antibiotic-induced changes in B. subtilis cells. Surprisingly, we found that the ribosome inhibitor tetracycline causes membrane deformations. Further investigations showed that tetracycline disturbs membrane organization and localization of the peripheral membrane proteins MinD, MinC, and MreB. These observations are not the result of ribosome inhibition but constitute a secondary antibacterial activity of tetracycline that so far has defied discovery.

AQUEOUS SYNTHESIS OF HIGH QUANTUM YIELD AND MONODISPERSED THIOL-CAPPED CdxZn1-xTe QUANTUM DOTS BASED ON ELECTROCHEMICAL METHOD

NANO ◽  
2012 ◽  
Vol 07 (02) ◽  
pp. 1250011 ◽  
Author(s):  
JUNWEI LI ◽  
YANG JIANG ◽  
YUGANG ZHANG ◽  
DI WU ◽  
ANQI LUO ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Quantum Yield ◽  
Electrochemical Method ◽  
Large Scale ◽  
Ostwald Ripening ◽  
Visible Absorption ◽  
Aqueous Synthesis ◽  
Transmission Electron

A facile green approach has been developed to control the growth regime in the aqueous synthesis of CdxZn1-xTe semiconductor quantum dots (QDs) based on the electrochemistry method. The Low growth temperature and slow injection of Te precursor are used to prolong the diffusion controlled stage and thus suppress Ostwald ripening during the nanocrystal growth. The experimental results showed that a low concentration of Te precursor will definitely influence the growth procedure. The UV–visible absorption spectra, as well as transmission electron microscopy (TEM) shows the QDs a good monodispersity at any interval of the reaction procedure. The high-resolution transmission electron microscopy (HRTEM) images and powder X-ray diffraction (XRD) pattern suggested that the as-prepared QDs have high crystallinity and cubic structure. The size and composition-dependent fluorescent emission wavelength of the resultant CdxZn1-xTe alloyed QDs can be tuned from 460 to 610 nm, and their photoluminescent quantum yield can reach up to 70%. Especially in the wavelength range of 510–578 nm, the overall PL QYs of the as-prepared CdxZn1-xTe QDs were above 50%. The current work suggests that electrochemical method is an attractive approach to the synthesis of high-quality II-VI ternary alloyed semiconductor QDs at large-scale with a prominent cost advantage.

Cleavage in the chick embryo

Development ◽  
1978 ◽  
Vol 43 (1) ◽  
pp. 55-69
Author(s):  
Ruth Bellairs ◽  
F. W. Lorenz ◽  
Tania Dunlap
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chick Embryo ◽  
Cell Membrane ◽  
Cortical Region ◽  
Chick Embryos ◽  
Membrane Formation ◽  
Transmission Electron

Chick embryos ranging from the stage of first cleavage to that of about 700 cells were removed from the oviduct and examined by transmission electron microscopy. Beneath the cell membrane is a yolk-free cortical region containing microfilaments. Beneath this lies cytoplasm which contains yolk spheres which are graded in size, the dorsal ones being smaller than the ventral ones. The subgerminal periblast possesses a greater proportion of yolk to cytoplasm than do the cells proper, but it merges with the cytoplasm at the incomplete borders of the ‘open’ cells. Specialized accumulations of membranes lie in the marginal periblast, and it is suggested that they play a role in cell membrane formation.

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.

Ordering of InGaAs Quantum Dots Grown by Molecular Beam Epitaxy under As2 gas flux

2015 ◽  
Vol 1792 ◽  
Author(s):  
Mourad Benamara ◽  
Yuriy I. Mazur ◽  
Peter Lytvyn ◽  
Morgan E. Ware ◽  
Vitaliy Dorogan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Quantum Dots ◽  
Atomic Force Microscopy ◽  
Molecular Beam Epitaxy ◽  
Large Scale ◽  
Molecular Beam ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron

ABSTRACTThe influence of the substrate temperature on the morphology and ordering of InGaAs quantum dots (QD), grown on GaAs (001) wafers by Molecular Beam Epitaxy (MBE) under As2 flux has been studied using Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and Photoluminescence (PL) measurements. The experimental results show that lateral and vertical orderings occur for temperatures greater than 520°C and that QDs self-organize in a 6-fold symmetry network on (001) surface for T=555°C. Vertical orderings of asymmetric QDs, along directions a few degrees off [001], are observed on a large scale and their formation is discussed.

scholarly journals Growth Mechanism of Periodic-Structured MoS2 by Transmission Electron Microscopy

Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 135
Author(s):  
Arvind Mukundan ◽  
Yu-Ming Tsao ◽  
Sofya B. Artemkina ◽  
Vladimir E. Fedorov ◽  
Hsiang-Chen Wang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Growth Mechanism ◽  
Large Scale ◽  
Periodic Structures ◽  
Chemical Vapor ◽  
Composition Analysis ◽  
Transmission Electron ◽  
Growth Phenomenon ◽  
Periodic Growth

Molybdenum disulfide (MoS2) was grown on a laser-processed periodic-hole sapphire substrate through chemical vapor deposition. The main purpose was to investigate the mechanism of MoS2 growth in substrate with a periodic structure. By controlling the amount and position of the precursor, adjusting the growth temperature and time, and setting the flow rate of argon gas, MoS2 grew in the region of the periodic holes. A series of various growth layer analyses of MoS2 were then confirmed by Raman spectroscopy, photoluminescence spectroscopy, and atomic force microscopy. Finally, the growth mechanism was studied by transmission electron microscopy (TEM). The experimental results show that in the appropriate environment, MoS2 can be successfully grown on substrate with periodic holes, and the number of growth layers can be determined through measurements. By observing the growth mechanism, composition analysis, and selected area electron diffraction diagram by TEM, we comprehensively understand the growth phenomenon. The results of this research can serve as a reference for the large-scale periodic growth of MoS2. The production of periodic structures by laser drilling is advantageous, as it is relatively simpler than other methods.

scholarly journals An Improved Fixation Method for Transmission Electron Microscopy for the Histological Study of the Lens

1991 ◽  
Vol 68 (5) ◽  
pp. 295-298 ◽  
Author(s):  
Hideki SAKAI ◽  
Kuniaki TAKATA ◽  
Minoru FUKUDA ◽  
Takaaki FUJIWARA ◽  
Hiroshi HIRANO
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Histological Study ◽  
Fixation Method ◽  
Transmission Electron

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.

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