Ultrastructure of Staphylococcus epidermidis after freeze-etching and thin sectioning

1973 ◽  
Vol 19 (2) ◽  
pp. 294-295
Author(s):  
James E. Gilchrist ◽  
Irving W. DeVoe
Keyword(s):  
Staphylococcus Aureus ◽  
Outer Layer ◽  
Staphylococcus Epidermidis ◽  
Cell Walls ◽  
Cytoplasmic Membrane ◽  
Middle Layer ◽  
Dense Layer ◽  
Thin Sections ◽  
Thin Sectioning ◽  
Freeze Etching

A considerable quantity of information is now available on the ultrastructure of Staphylococcus (1, 2, 4, 7, 8, 10, 11, 12). Cell walls of these organisms in thin sections have been shown to consist of three layers: a dense outer layer, a rather electron translucent middle layer, and a very dense layer next to the cytoplasmic membrane (2, 7, 11, 12). Bulger and Bulger (2) have pointed out the presence of circumferential substructure in the middle layer of the wall in a strain of Staphylococcus aureus isolated as the causative agent in fatal pneumonia.Numerous mesosomes of both the vesicular and laminar types are evident in thin sections of staphylococci from several studies (1, 4, 7, 11). Moreover, single vesicular structures that appear to be invaginations of the trilaminar cytoplasmic membrane have been pointed out by Suganuma (11) and Beaton (1).

Comparative ultrastructure of selected oral streptococci: thin-sectioning and freeze-etching studies

1976 ◽  
Vol 22 (4) ◽  
pp. 475-485 ◽  
Author(s):  
Stanley C. Holt ◽  
E. R. Leadbetter
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Cytoplasmic Membrane ◽  
Close Association ◽  
Oral Streptococci ◽  
Outermost Layer ◽  
Thin Sectioning ◽  
Freeze Etching ◽  
Comparative Ultrastructure ◽  
Crystalline Array

The ultrastructure of Streptococcus mutans, serotypes a–e, S. sanguis, S. mitis, and S. salivarius HHT, were examined by the techniques of thin-sectioning and freeze-etching. The cell walls varied in width between 15 and 46 nm and were covered with an electron-dense fibrillar or fuzz layer. The cytoplasmic membrane was in close association with numerous mesosomes which were, in turn, either closely associated or in contact with the bacterial chromosome. In freeze-etch replicas, the outermost layer of the cell wall was fibrous, and the cytoplasmic membrane was covered with particles composed of several subunits. Both particle-clusters and particle-free areas occurred on the surfaces of the cytoplasmic membrane, as well as a crystalline array in the ground plasm of the cell.

Review — The Orientation of Cellulose Microfibrils in the cell walls of Tracheids in Conifers

IAWA Journal ◽  
2005 ◽  
Vol 26 (2) ◽  
pp. 161-174 ◽  
Author(s):  
Hisashi Abe ◽  
Ryo Funada
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Outer Layer ◽  
Cell Walls ◽  
Secondary Wall ◽  
Middle Layer ◽  
Cellulose Microfibrils ◽  
Conifer Species ◽  
Predominant Orientation ◽  
Scanning Electron

We examined the orientation of cellulose microfibrils (Mfs) in the cell walls of tracheids in some conifer species by field emission-scanning electron microscopy (FE-SEM) and developed a model on the basis of our observations. Mfs depositing on the primary walls in differentiating tracheids were not well-ordered. The predominant orientation of the Mfs changed from longitudinal to transverse, as the differentiation of tracheids proceeded. The first Mfs to be deposited in the outer layer of the secondary wall (S1 layer) were arranged as an S-helix. Then the orientation of Mfs changed gradually, with rotation in the clockwise direction as viewed from the lumen side of tracheids, from the outermost to the innermost S1 layer. Mfs in the middle layer of the secondary wall (S2 layer) were oriented in a steep Z-helix with a deviation of less than 15° within the layer. The orientation of Mfs in the inner layer of the secondary wall (S3 layer) changed, with rotation in a counterclockwise direction as viewed from the lumen side, from the outermost to the innermost S3 layer. The angle of orientation of Mfs that were deposited on the innermost S3 layer varied among tracheids from 40° in a Z-helix to 20° in an S-helix.

Ultrastructural comparisons of fungus hyphal cells using frozen-etched replicas and thin sections of the fungus Pyrenochaeta terrestris

1968 ◽  
Vol 14 (3) ◽  
pp. 205-210 ◽  
Author(s):  
W. M. Hess
Keyword(s):  
Electron Scattering ◽  
Cell Walls ◽  
Sole Carbon Source ◽  
Membrane Systems ◽  
Thin Sections ◽  
Fixed Membrane ◽  
Pyrenochaeta Terrestris ◽  
Freeze Etching ◽  
Fixed Cell ◽  
Etched Membrane

The ultrastructure of P. terrestris hyphal cells was investigated to compare frozen-etched replicas with chemically fixed thin sections. The fungus used in this study uses glycerol as a sole carbon source and survives the freezing procedures necessary for freeze-etching; thus frozen-etched replicas reflect the living state.Frozen-etched membrane systems have particles of various sizes and concentrations and have a smooth appearance as contrasted to chemically fixed membrane systems, which have particles difficult to distinguish and somewhat irregular membrane systems. Frozen-etched cell walls are seen to contain particles, and microfibrillar orientation is evident in older cell walls, whereas substructure is not evident in chemically fixed cell walls, although secretion products of the fungus accumulate on cell surfaces.Chemically fixed ground cytoplasm has ribosomes and areas of high- and low-electron scattering which are not seen with freeze-etching. Cells fixed in glutaraldehyde–acrolein–OsO4 more nearly resemble frozen-etched cells than cells fixed in potassium permanganate.

Ultrastructure of the cell envelope and septation process in Caryophanon latum as revealed by thin section and freeze-etching techniques

1974 ◽  
Vol 20 (10) ◽  
pp. 1435-1442 ◽  
Author(s):  
W. C. Trentini ◽  
H. E. Gilleland Jr.
Keyword(s):  
Cytoplasmic Membrane ◽  
External Surface ◽  
Cell Envelope ◽  
Optimal Conditions ◽  
Structural Detail ◽  
Cross Sectional ◽  
External Wall ◽  
Thin Sectioning ◽  
Freeze Etching ◽  
Peptidoglycan Layer

With optimal conditions of thin-sectioning and freeze-etching, the cell wall of Caryophanon latum was composed of a thick peptidoglycan layer plus two external wall layers. The freeze-etched appearance of the external surface of the outer layer was smooth and lacked structural detail. The numerous cross septa within a trichome were formed by the symmetrical and concurrent ingrowth of the cytoplasmic membrane and the peptidoglycan layer. The site of septum initiation was identifiable by a dart-shaped ingrowth of the peptidoglycan layer rather than by the presence of a mesosome. However, small simple mesosomes were occasionally seen associated with the developing septum. The peptidoglycan in the septum had thickened to at least double the thickness of the wall peptidoglycan layer by the time of septum completion. The external wall layers did not participate in septum formation but did participate in trichome separation. The separation of the septal peptidoglycan was completed during the early ingrowth of the external wall layers. A unique cross-sectional view of a developing septum closing like an iris diaphragm as seen in a freeze-etched preparation was observed.

scholarly journals ULTRASTRUCTURE AND CALCIUM TRANSPORT IN CRUSTACEAN MUSCLE MICROSOMES

1971 ◽  
Vol 48 (1) ◽  
pp. 49-60 ◽  
Author(s):  
R. J. Baskin
Keyword(s):  
Freeze Drying ◽  
Calcium Uptake ◽  
Membrane Thickness ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Crustacean Muscle ◽  
Thin Sectioning ◽  
Critical Point Drying ◽  
Freeze Etching ◽  
Microscopic Techniques

Fragmented sarcoplasmic reticulum (FSR) from crustacean muscle was examined following preparation by a variety of electron microscopic techniques. The 30–40 A particles which appeared on the outer surface of FSR vesicles following negative staining were not observed following preparation by freeze-drying, freeze-etching, thin sectioning, or critical-point drying. Crustacean FSR exhibited high values of calcium uptake and extensive nodular formation in the presence of oxalate. 80–90 A diameter membrane particles were seen in freeze-etch preparations of both intact lobster muscle and FSR vesicles. Thin sections of FSR vesicles revealed a membrane thickness of 60–70 A. The membrane appeared to be triple layered, each layer having a thickness of 20–25 A.

Fine structure of the macroconidia of Fusarium solani

1975 ◽  
Vol 53 (19) ◽  
pp. 2134-2146 ◽  
Author(s):  
J. P. Tewari ◽  
W. P. Skoropad
Keyword(s):  
Cell Wall ◽  
Fusarium Solani ◽  
Superficial Layer ◽  
Dense Layer ◽  
Inoculum Potential ◽  
Chemical Fixation ◽  
Thin Sections ◽  
Innermost Layer ◽  
Freeze Etching ◽  
Myelin Figures

Ultrastructure of the macroconidia of Fusarium solani as visualized by transmission (ultrathin sectioning and freeze-etching) and scanning electron microscopy is described. The cell wall has four layers. The innermost layer is electron-lucid followed by an electron-dense layer. The next outer layer is spongy in appearance followed by a superficial layer consisting of fine filamentous processes. Freeze-etch replicas of conidia directly removed from the sporodochia and still suspended in the mucilaginous material (in which they are produced) frequently show the conidia connected by the superficial filamentous processes in the cell wall. This agglutination of the conidia is likely to increase the inoculum potential of this pathogen at the sites of infection. Structure of various membrane systems in the cells is described. The endoplasmic reticulum is fairly extensive and fenestrated. Thin sections of routinely fixed conidia show myelin figures. However, such structures were not seen in replicas of conidia that were freeze-etched without use of chemical fixation or cryoprotection.

Teliospores of Entorrhiza casparyana (Ustilaginales): a correlated thin-sectioning and freeze–fracture study of endogenously dormant spores

1984 ◽  
Vol 62 (12) ◽  
pp. 2525-2539 ◽  
Author(s):  
Brian A. Fineran ◽  
Judith M. Fineran
Keyword(s):  
Outer Layer ◽  
Freeze Fracture ◽  
Middle Layer ◽  
Wall Material ◽  
Lipid Bodies ◽  
Freeze Fracturing ◽  
Thin Sectioning ◽  
Single Nucleus ◽  
Fracture Study ◽  
Small Clusters

A correlated thin-sectioning and freeze–fracturing approach was used to reveal the ultrastructure of endogenously dormant teliospores in the smut fungus Entorrhiza casparyana (Magn.) Lagerh. Conventional fixation and embedding methods yielded poor preservation of the wall and protoplasm. Successful preservation was achieved by fixing frozen and cryosectioned spores in glutaraldehyde and subsequently processing by standard procedures for transmission electron microscopy. Freeze–fracturing provided cross- and contour-fractured views of the protoplasm and the different layers of the wall. The wall is thick, consisting of three main layers: outer, middle, and inner, with the outer and inner layers further differentiated into zones. The warty zone dominates the outer layer and consists of radial protuberances (warts) with the regions between filled to varying degrees with similar wall material containing electron-transparent lamellae. The extent of differentiation of the warty zone is reflected in the surface morphology of the spores, which ranges from verrucose to almost smooth. At the base of the outer layer is an electron-translucent irregular zone. The middle and inner layers are regular in thickness around the spore, with the middle layer being the most electron dense. The inner layer is differentiated into three zones. The most distinctive is zone 2 which in freeze–fractured walls has an unique mosaic of striae. Cytochemical staining of the wall for polysaccharide material gives a positive reaction only for the warty zone. The protoplasm contains a single nucleus and is dominated by numerous spheroidal storage lipid bodies. Squeezed among the lipid bodies are organelles, believed to be microbodies, containing a granular matrix and often electron-transparent areas. These organelles failed to show catalase activity with the 3,3′-diaminobenzidine method. Occasional short profiles of endoplasmic reticulum cisternae, a few mitochondria with sparse cristae, dispersed small clusters of glycogen, and sometimes scattered ribosomes are also present in the cytoplasm. All these features are typical of dormant spores with a low metabolic activity.

Some histochemical features of anther wall of Leucojum aestivum (Amaryllidaceae) during pollen development

Biologia ◽  
2012 ◽  
Vol 67 (5) ◽  
Author(s):  
Nuran Ekici ◽  
Feruzan Dane
Keyword(s):  
Cell Walls ◽  
Cell Activation ◽  
Developmental Stages ◽  
Middle Layer ◽  
Point Of View ◽  
Anther Wall ◽  
Vascular Bundles ◽  
Thin Sections ◽  
Leucojum Aestivum ◽  
Rna Content

AbstractIn this study, polysaccharide and RNA contents of anthers were investigated on different phases of sporogenesis by using light microscopy techniques from histological and cytological point of view in Leucojum aestivum. Paraffin and semi-thin sections of anthers were stained with toluidine blue and PAS. Anthers were tetrasporangiate. The wall of the anther consists of an epidermis, endothecium, middle layer and glandular tapetum. During one nucleated microspore and mature pollen phase microspores and tapetum cells began to degenerate and they were become very rich of RNA in L. aestivum. And also RNA content was increased in endothecium and middle layer cells except the epidermis cells of anther wall. An increase in RNA content indicates cell activation. Polysaccharides were not seen in young anther wall but they were seen in older ones. They were generally condensed in the cell walls and especially in the cell walls of vascular bundles of connective tissue. This could be thought that insoluble polysaccharides were used in metabolic events in early developmental stages. Appearance of polysaccharides in late phases was indicated that polysaccharides were used in the formation of cuticule and differentiation of endothelium cell walls.

Use of detergents to facilitate penetration of fixatives into thick-walled fungal spores

1978 ◽  
Vol 36 (2) ◽  
pp. 400-401
Author(s):  
Mercedes R. Edwards
Keyword(s):  
Potassium Permanganate ◽  
Cell Walls ◽  
Fungal Spores ◽  
Thin Sections ◽  
Cell Structures ◽  
Thin Sectioning ◽  
Aerial Hyphae ◽  
Plastic Embedding

Fungi are difficult to prepare for good ultra-thin sectioning. Aerial hyphae and certain types of spores have rigid layered walls with outer coats relatively impermeable to common fixatives such as glutaraldehyde and osmium. The slow penetration of these reagents into the cell apparently leads to the formation of artifacts (e. g., mycelin figures and vesicular systems) indicating bad fixation. Poor plastic embedding ensues and many holes are found in the sections, around cell walls or within the cells. Obtaining suitable thin sections from such materials is almost impossible. This problem has been overcome in part by the use of potassium permanganate, which penetrates fungal cells readily and produces good outline of membranes. However, this fixative can destroy most of the cytoplasmic and nuclear matrices and thus is not adequate for the preservation of ribosomes and other cell structures.

Ultrastructural changes in the conidia of Penicillium notatum during germination

1973 ◽  
Vol 19 (7) ◽  
pp. 797-801 ◽  
Author(s):  
J. F. Martin ◽  
F. Uruburu ◽  
J. R. Villanueva
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Ultrastructural Changes ◽  
Dense Layer ◽  
Penicillium Notatum ◽  
Thin Sections ◽  
Resting Spores ◽  
Different Types ◽  
Germ Tubes ◽  
Isolated Cell

To study the changes in the cell wall of Penicillium notatum during germination, thin sections of resting, swollen, and germinating spores, and mycelium were compared with thin sections of the isolated cell walls. In the cell wall of resting spores four distinct layers were found. The outermost layer of the cell wall of resting spores was released during swelling and the two inner layers were extended to form the cell wall of the germ tube. The cell wall of young germ tubes had only two layers but a new electron-dense layer was formed later on the outside. Mycelial cell walls which appeared thinner than those of conidia showed three distinct layers. Large mitochondria that divide during germination were present in both resting and swollen spores. Two different types of vacuoles were found, both of which decreased in size and in number during germination. Endoplasmic reticulum was almost absent in resting spores but increased substantially during swelling.

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