Scanning Electron Microscope: Potentials in the Morphology of Microorganisms

Bartlett, Grant A.

doi:10.1126/science.158.3806.1318

Cited by 23 publications

(5 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This phenomena was examined using scanning electron microscopy in order to visualize antibiotic-induced morphological changes. A number of previous studies have substantiated the utility of scanning electron microscopy for examining the surface morphology of microorganisms (Bartlett, 1967;Barnes et al, 1971;Klainer and Perkins, 1971) and this technique has been used to study antibiotic-induccd changes in the surface of microorganisms (Greenwood and O'Grady, 1969). The critical point drying technique was used in this study because it provides the most artifact-free method for sample preparation with maintenance of cell size and dimensions.…”

Section: Resultsmentioning

confidence: 99%

Disruption of Escherichia coli outer membranes by EM 49. A new membrane active peptide antibiotic

1976

View full text Add to dashboard Cite

A new peptide antibiotic, EM 49, is shown to disrupt the structure of Escherichia coli outer membranes and release outer membrane fragments into the surrounding media. Evidence supporting this conclusion indludes EM 49 stimulated release of outer membrane phospholipids, lipopolysaccharide, and membrane fragments having a phospholipid and polypeptide composition similar to outer membranes. The density of the membrane fragments released by EM 49 was 1.22 g/cm3, which was identical to isolated outer membranes. Approximately 10 to 15% of the E. coli lipopolysaccharide was released upon treatment with EM 49. Both scanning and transmission electron microscopy revealed that the antibiotic caused the formation of numerous protrusions or blebs on the surface of E. coli with apparent release of membrane vesicles from the cells. Direct interaction between EM 49 and outer membranes was demonstrated using outer membranes labeled with the fluorescent dye diphenylhexatriene. Treatment of the fluorescent-labeled outer membranes with EM 49 increased fluorescence intensity and decreased polarization, indicating that the peptide perturbed outer-membrane structure. In addition, strong interactions between EM 49 and purified E. coli phospholipids were detected using the Hummel and Dreyer technique. Association constants between the peptide and phospholipids were approximately 10(5) M-1. A model for the disruptive effect of EM 49 on outer-membrane structure is proposed in which the fatty acid chain of the antibiotic is inserted into the hydrophobic core of the membrane. This orientation would allow the polycationic, peptide portion of the antibiotic to disrupt the antibiotic to disrupt the normal electrostatic interactions between divalent cations and components of the outer membrane. Evidence supporting this conclusion includes specific protection of E. coli from EM 49 by Mg2+ and Ca2+ and inhibition of EM 49 stimulated phospholipid release by these cations. Disruption of the antibiotic to penetrate to the inner membrane, which is probably the primary killing site of EM 49.

show abstract

Section: Resultsmentioning

confidence: 99%

Disruption of Escherichia coli outer membranes by EM 49. A new membrane active peptide antibiotic

1976

View full text Add to dashboard Cite

show abstract

“…Scanning electron microscopy (SEM) has been used effectively in studying the morphological changes during the growth of other microorganisms (3,6,9). In the present study, we in a critical-point bomb (5; R. S. Merkal et al, Amer.…”

mentioning

confidence: 99%

Scanning Electron Microscopy of the H37Ra Strain of Mycobacterium tuberculosis Exposed to Isoniazid

Takayama

Wang

Merkal

1973

Antimicrob Agents Chemother

View full text Add to dashboard Cite

The morphology of cells of the H37Ra strain of Mycobacterium tuberculosis exposed to 0.5 μg of isonicotinic acid hydrazide (isoniazid) per ml was examined by scanning electron microscopy (SEM). Cells that were exposed to isoniazid for 3 h showed no detectable change, whereas cells exposed to the drug for 24 h exhibited diverse morphological features. From our examination of these SEM pictures, we have reconstructed the probable sequence of morphological changes to be as follows: (i) the wrinkling of the cell surface was ascribed as the earliest observable change, (ii) the cell surface then became very rough and ragged, (iii) eventually the cytoplasmic material was extruded from the cell, (iv) this event produced a collapsed cell, (v) the cells began to fragment, (vi) the fragmented cells then coalesced to form an amorphous mass of cell debris.

show abstract

“…One powerful approach for the identification and classification of microorganisms is optical and electron microscope imaging of their morphology and intracellular organelles [5,6]. On the other hand, gene amplification and sequencing of DNA and RNA have been adopted as important tools for classifying a broad range of bacteria and fungi targets.…”

Section: Introductionmentioning

confidence: 99%

Identifying different types of microorganisms with terahertz spectroscopy

Yoon

Jun

et al. 2019

Biomed. Opt. Express

View full text Add to dashboard Cite

Most microbial detection techniques require pretreatment, such as fluorescent labeling and cultivation processes. Here, we propose novel tools for classifying and identifying microorganisms such as molds, yeasts, and bacteria based on their intrinsic dielectric constants in the THz frequency range. We first measured the dielectric constant of films that consisted of a wide range of microbial species, and extracted the values for the individual microbes using the effective medium theory. The dielectric constant of the molds was 1.24-1.85, which was lower than that of bacteria ranging from 2.75-4.11. The yeasts exhibited particularly high dielectric constants reaching 5.63-5.97, which were even higher than that of water. These values were consistent with the results of low-density measurements in an aqueous environment using microfluidic metamaterials. In particular, a blue shift in the metamaterial resonance occurred for molds and bacteria, whereas the molds have higher contrast relative to bacteria in the aqueous environment. By contrast, the deposition of the yeasts induced a red shift because their dielectric constant was higher than that of water. Finally, we measured the dielectric constants of peptidoglycan and polysaccharides such as chitin, α-glucan, and β-glucans (with short and long branches), and confirmed that cell wall composition was the main cause of the observed differences in dielectric constants for different types of microorganisms.

show abstract

Scanning Electron Microscope: Potentials in the Morphology of Microorganisms

Cited by 23 publications

References 6 publications

Disruption of Escherichia coli outer membranes by EM 49. A new membrane active peptide antibiotic

Disruption of Escherichia coli outer membranes by EM 49. A new membrane active peptide antibiotic

Scanning Electron Microscopy of the H37Ra Strain of Mycobacterium tuberculosis Exposed to Isoniazid

Identifying different types of microorganisms with terahertz spectroscopy

Contact Info

Product

Resources

About