scholarly journals Electron microscopy reveals unexpected cytoplasm and envelope changes during thymineless death in Escherichia coli

2021 ◽  
Author(s):  
T.V. Pritha Rao ◽  
Andrei Kuzminov
Keyword(s):  
Electron Microscopy ◽  
Dna Replication ◽  
Morphological Changes ◽  
Cell Envelope ◽  
Microscopy Study ◽  
Negative Control ◽  
Chromosome Damage ◽  
Chromosomal Damage ◽  
E Coli ◽  
Thymineless Death

Bacterial rod-shaped cells experiencing irreparable chromosome damage should filament without other morphological changes. Thymineless death (TLD) strikes thymidine auxotrophs denied external thymine/thymidine (T) supplementation. Such T-starved cells cannot produce the DNA precursor dTTP and therefore stop DNA replication. Stalled replication forks in T-starved cells were always assumed to experience mysterious chromosome lesions, but recently TLD was found to be independent of origin-dependent DNA replication, with the chromosome still remaining the main TLD target. T-starvation also induces morphological changes, as if thymidine prevents cell envelope or cytoplasm problems that otherwise translate into chromosome damage. We used transmission electron microscopy to examine cytoplasm and envelope changes in T-starved E. coli cells, using treatment with a DNA gyrase inhibitor as a control for "pure" chromosome death. Besides the expected cell filamentation in response to both treatments, we see the following morphological changes specific for T-starvation, that might lead to chromosome damage: 1) significant cell widening; 2) nucleoid diffusion; 3) cell pole damage; 4) formation of numerous cytoplasmic bubbles. We conclude that T-starvation does impact both the cytoplasm and the cell envelope in ways that could potentially affect the chromosome. Importance Thymineless death is a dramatic and medically-important phenomenon, whose mechanisms remain a mystery. Unlike most other auxotrophs in the absence of the required supplement, thymidine-requiring E. coli mutants not only go static in the absence of thymidine, but rapidly die of chromosomal damage of unclear nature. Since this chromosomal damage is independent of replication, we examined fine morphological changes in cells undergoing thymineless death in order to identify what could potentially affect the chromosome. We report several cytoplasm and cell envelope changes that develop in thymidine-starved cells, but not in gyrase-inhibitor-treated cells (negative control), that could be linked to subsequent irreparable chromosome damage. This is the first electron microscopy study of cell undergoing "genetic death" due to irreparable chromosome lesions.

scholarly journals Atomic Force Microscopy Study of the Effect of Antimicrobial Peptides on the Cell Envelope of Escherichia coli

2005 ◽  
Vol 49 (10) ◽  
pp. 4085-4092 ◽  
Author(s):  
M. Meincken ◽  
D. L. Holroyd ◽  
M. Rautenbach
Keyword(s):  
Escherichia Coli ◽  
Atomic Force Microscopy ◽  
Morphological Changes ◽  
Cell Envelope ◽  
Microscopy Study ◽  
Target Cells ◽  
Force Microscopy ◽  
E Coli ◽  
Atomic Force ◽  
Before And After

ABSTRACT The influences of the antibacterial magainin 2 and PGLa from the African clawed frog (Xenopus laevis) and the hemolytic bee venom melittin on Escherichia coli as the target cell were studied by atomic force microscopy (AFM). Nanometer-scale images of the effects of the peptides on this gram-negative bacterium's cell envelope were obtained in situ without the use of fixing agents. These high-resolution AFM images of the surviving and intact target cells before and after peptide treatment showed distinct changes in cell envelope morphology as a consequence of peptide action. Although all three peptides are lytic to E. coli, it is clear from this AFM study that each peptide causes distinct morphological changes in the outer membrane and in some cases the inner membrane, probably as a consequence of different mechanisms of action.

Replication of Bacteriophage 186 DNA

1972 ◽  
Vol 30 ◽  
pp. 194-195
Author(s):  
Dhruba K. Chattoraj ◽  
Ross B. Inman
Keyword(s):  
Electron Microscopy ◽  
Dna Replication ◽  
Frame Of Reference ◽  
Dna Molecules ◽  
E Coli ◽  
Phage Dna ◽  
Partial Denaturation

Electron microscopy of replicating intermediates has been quite useful in understanding the mechanism of DNA replication in DNA molecules of bacteriophage, mitochondria and plasmids. The use of partial denaturation mapping has made the tool more powerful by providing a frame of reference by which the position of the replicating forks in bacteriophage DNA can be determined on the circular replicating molecules. This provided an easy means to find the origin and direction of replication in λ and P2 phage DNA molecules. DNA of temperate E. coli phage 186 was found to have an unique denaturation map and encouraged us to look into its mode of replication.

Interaction of Gram-Negative Bacteria with the Lysosomal Fraction of Polymorphonuclear Leukocytes II. Changes in the Cell Envelope of Escherichia coli

1970 ◽  
Vol 1 (3) ◽  
pp. 311-318
Author(s):  
D. Friedberg ◽  
I. Friedberg ◽  
M. Shilo
Keyword(s):  
Escherichia Coli ◽  
Polymorphonuclear Leukocytes ◽  
Cytoplasmic Membrane ◽  
Morphological Changes ◽  
Cell Envelope ◽  
Gram Negative Bacteria ◽  
Intact Cells ◽  
Lysosomal Fraction ◽  
E Coli ◽  
Absorbing Material

Interaction of lysosomal fraction with Escherichia coli caused damage to the cell envelope of these intact cells and to the cytoplasmic membrane of E. coli spheroplasts. The damage to the cytoplasmic membrane was manifested in the release of 260-nm absorbing material and β-galactosidase from the spheroplasts, and by increased permeability of cryptic cells to O -nitrophenyl-β- d -galactopyranoside; damage to the cell wall was measured by release of alkaline phosphatase. Microscope observation showed morphological changes in the cell envelope.

scholarly journals Electron microscopy study of the alteration of P‐fimbriated E. coli adhesion to human uroepithelial cells

2012 ◽  
Vol 26 (S1) ◽  
Author(s):  
Lindsey L Kimble ◽  
Bridget D Mathison ◽  
Kerrie L Kaspar ◽  
Christina Khoo ◽  
Boon P Chew
Keyword(s):  
Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
E Coli ◽  
Uroepithelial Cells

scholarly journals Fabrication & Characterization of Chitosan Coated Biologically Synthesized TiO2 Nanoparticles against PDR E. coli of Veterinary Origin

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Naheed Zafar ◽  
Bushra Uzair ◽  
Muhammad Bilal Khan Niazi ◽  
Shamaila Sajjad ◽  
Ghufrana Samin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Antibacterial Activity ◽  
Titanium Dioxide ◽  
Morphological Changes ◽  
Titanium Dioxide Nanoparticles ◽  
Chitosan Nanoparticles ◽  
Diffusion Method ◽  
Potential Threat ◽  
E Coli

Treatment of pandrug resistant (PDR) Escherichia coli strain is the leading causative agent of bovine mastitis worldwide. Hence, becoming a potential threat to veterinary and public health. Therefore, to control the infection new nontoxic, biocompatible antimicrobial formulation with enhanced antibacterial activity is massively required. Current study was planned to synthesize chitosan coated titanium dioxide nanoparticles (CS-NPs coated TiO2). Coating was being done by chitosan nanoparticles (CS-NPs) using ionic gelation method. Aqueous solution of Moringa concanensis leaf extract was used to synthesize titanium dioxide nanoparticles (TiO2 NPs). The synthesized nanoformulations were characterized by using XRD, SEM, and FTIR. X-ray diffraction (XRD) analysis indicated the crystalline phase of TiO2 NPs and CS-NPs coated TiO2 NPs. Scanning Electron Microscopy (SEM) confirmed spherical shaped nanoparticles size of chitosan NPs ranging from 19–25 nm and TiO2 NPs 35–50 nm. Thesize of CS-NPs coated TiO2 NPs was in the range of 65–75 nm. The UV-Vis Spectra and band gap values illustrated the red shift in CS-NPs coated TiO2 NPs. Fourier transform infrared (FTIR) spectroscopy confirmed the linkages between TiO2 NPs and chitosan biopolymer, Zeta potential confirmed the stability of CS-NPs coated TiO2 NPs by showing 95 mV peak value. In-vitro antibacterial activity of CS-NPs coated TiO2 NPs and Uncoated TiO2 NPs was evaluated by disc diffusion method against PDR strain of E. coli isolated from mastitic milk samples. The antibacterial activity of all the synthesized nanoformulations were noted and highest antibacterial activity was shown by CS-NPs coated TiO2-NPs against pandrug resistant (PDR) E. coli strain with the prominent zone of inhibition of 23 mm. Morphological changes of E. coli cells after the treatment with MIC concentration (0.78 μg/ml) of CS-NPs coated TiO2 NPs were studied by transmission electron microscopy TEM showedrigorous morphological defectand has distorted the general appearance of the E. coli cells. Cytotoxicity (HepG2 cell line) and hemolytic (human blood) studies confirmed nontoxic/biocompatible nature of CS-NPs coated biologically synthesized TiO2 NPs. The results suggested that biologically synthesized and surface modified TiO2 NPs by mucoadhesive polysaccharides (e.g. chitosan) coating would be an effective and non-toxic alternative therapeutic agent to be used in livestock industry to control drug resistant veterinary pathogens.

scholarly journals Increasing the Shelf Life of Milk by Metal Oxide Nanoparticles and Mild Heat

2020 ◽  
Author(s):  
Mahbooubeh Mirhosseini ◽  
Roghayeh Dehestani
Keyword(s):  
Electron Microscopy ◽  
Antimicrobial Activity ◽  
Metal Oxide ◽  
Pathogenic Bacteria ◽  
Morphological Changes ◽  
Synergistic Effects ◽  
Metal Oxide Nanoparticles ◽  
Oxide Nanoparticles ◽  
E Coli ◽  
Mild Heat

Background: The spread of pathogenic microorganisms in food and beverage and their resistance to antibiotics have raised major concerns for public health. The aim of this study was to investigate the antimicrobial activity of various metal oxide nanoparticles (NPs) including zinc oxide (ZnO), magnesium oxide (MgO), and iron oxide (Fe2O3) NPs against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Furthermore, the antimicrobial activity of these NPs in milk was studied along with mild heat. Methods: In this experimental study, the antibacterial activity of ZnO, MgO, and Fe2O3 NPs were initially evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Later, the antimicrobial effect of these NPs was investigated in milk along with mild heating. To determine the morphological changes in S. aureus and E. coli, electron microscopy scanning was applied before and after the antimicrobial treatments. Results: The MBC and MIC values presented by Fe2O3, ZnO, and MgO NPs against pathogenic bacteria showed that MgO NPs were the most potent substances for inhibiting the growth of S. aureus and E. coli. The results also indicated that use of these NPs had synergistic effects in combination with the heating treatment. Electron microscopy scanning also revealed that treatment with MgO NPs could distort and impair the cell wall of the pathogenic bacteria, leading to the leakage of intracellular components and bacterial death. Conclusion: The results suggest that MgO, ZnO, and Fe2O3 NPs can be applied for industrial food processing as effective antimicrobial compounds to decrease the temperature required for pasteurizing milk.

scholarly journals THE NEGATIVE CONTROL MECHANISM FOR E. coli DNA REPLICATION

1969 ◽  
Vol 63 (4) ◽  
pp. 1410-1417 ◽  
Author(s):  
B. H. Rosenberg ◽  
L. F. Cavalieri ◽  
G. Ungers
Keyword(s):  
Dna Replication ◽  
Control Mechanism ◽  
Negative Control ◽  
E Coli

scholarly journals SARS-CoV-2: High-Resolution Microscopy Study in Human Nasopharyngeal Samples.

2020 ◽  
Author(s):  
Brian Mondeja ◽  
Odalys Valdes ◽  
Sonia Resik ◽  
Ananayla Vizcaino ◽  
Emilio Acosta ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Microscopy Study ◽  
Negative Control ◽  
The Novel ◽  
Rt Pcr ◽  
Novel Coronavirus ◽  
High Resolution Microscopy ◽  
Scanning Electron

Abstract BackgroundThe novel coronavirus SARS-CoV-2 is the etiological agent of COVID-19. This virus has become one of the most dangerous in recent times with a very high rate of transmission. At present, several publications show the typical crown-shape of the novel coronavirus grown in cell cultures. However, an integral ultramicroscopy study done directly from clinical specimens has not been published. Methods Nasopharyngeal swabs were collected from two Cuban individuals, one asymptomatic and RT-PCR negative (negative control) and the other from a COVID-19 symptomatic and RT-PCR positive for SARS CoV-2. Samples were treated with an aldehyde solution and processed by Scanning Electron Microscopy, Confocal Microscopy and, Atomic Force Microscopy. Improvement and segmentation of coronavirus images were performed by mathematic algorithms. Results The images of the negative control sample showed the characteristic healthy microvilli morphology at the apical region of the nasal epithelial cells. As expected, they do not display virus-like structures. The images of the positive sample showed characteristic coronavirus-like particles and evident destruction of microvilli. In some regions, virions gemmating through the cell membrane were observed. Microvilli destruction could explain the anosmia reported by some patients. Virus-particles emerging from the cell-surface with a variable size ranging from 80 to 400 nm were observed by scanning electron microscopy (SEM). A confocal study showed viral antigen recognition in the apical cells zone. Conclusions The integral microscopy study showed that SARS-CoV-2 has a similar image to SARS-CoV. The application of several high-resolution microscopy techniques to clinical samples can help to answer important questions its replicative cycle and immunopathogenic mechanism of this novel coronavirus, relevant for the development of new treatments against this disease.

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