Light and electron microscopy of a host–fungus interaction in the roots of some epiphytic ferns from Costa Rica

1995 ◽  
Vol 73 (7) ◽  
pp. 991-996 ◽  
Author(s):  
E. Schmid ◽  
F. Oberwinkler ◽  
L. D. Gómez
Keyword(s):  
Electron Microscopy ◽  
Costa Rica ◽  
Matrix Material ◽  
Light And Electron Microscopy ◽  
Root Hairs ◽  
Host Cells ◽  
Cortical Cells ◽  
Host Fungus ◽  
Hyphal Coils ◽  
Uniform Diameter

The roots of 11 epiphytic fern species from the genera Elaphaglossum, Peltapteris, Hymenophyllum, Grammitis, and Lellingeria were studied by means of light and electron microscopy. All species showed a similar association with an ascomycete that traversed the root hairs and formed intracellular hyphal coils within cytoplasmic epidermal and outer cortical cells. The unbranched fungal hyphae were of a uniform diameter. They were surrounded by a flocculent matrix material and by the host plasmalemma. Cytoplasmic hyphae also occurred within degenerated host cells. The host–fungus interaction showed similarities to Ericoid mycorrhizae. Key words: ferns, mycorrhiza, ascomycete, ultrastructure, Costa Rica.

Light and electron microscopy of the host–fungus interaction in the achlorophyllous gametophyte of Botrychium lunaria

1994 ◽  
Vol 72 (2) ◽  
pp. 182-188 ◽  
Author(s):  
E. Schmid ◽  
F. Oberwinkler
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Key Words ◽  
Host Cell ◽  
Matrix Material ◽  
Light And Electron Microscopy ◽  
Thick Layer ◽  
Fungal Endophyte ◽  
Host Fungus ◽  
Translucent Material

The host–fungus interaction between the achlorophyllous gametophyte of Botrychium lunaria and its fungal endophyte was studied by means of light and electron microscopy. Aseptate hyphae with a multilayered cell wall formed intracellular coils. The interface consisted of a thick layer of fibrillar matrix material, an electron-translucent zone, and the host plasmalemma. Several vesicles that show different stages of development and degeneration occurred within one host cell. Degenerating vesicles were encased by large amounts of an electron-translucent material. Arbuscules were not observed. The fungus did not infect the young sporophyte but degenerated within intact gametophyte cells. Key words: Botrychium lunaria, gametophyte, mycorrhiza, ultrastructure.

Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust

1987 ◽  
Vol 65 (8) ◽  
pp. 1586-1598 ◽  
Author(s):  
L. Shain ◽  
U. Järlfors
Keyword(s):  
Electron Microscopy ◽  
Leaf Rust ◽  
Light And Electron Microscopy ◽  
Infection Process ◽  
The Other ◽  
Host Cells ◽  
Eastern Cottonwood ◽  
Melampsora Medusae ◽  
Wall Appositions ◽  
Infected Cells

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

scholarly journals AutoCLEM: An Automated Workflow for Correlative Live-Cell Fluorescence Microscopy and Cryo-Electron Tomography

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xiaofeng Fu ◽  
Jiying Ning ◽  
Zhou Zhong ◽  
Zandrea Ambrose ◽  
Simon Charles Watkins ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Speed ◽  
Electron Tomography ◽  
Light And Electron Microscopy ◽  
Live Cell ◽  
Host Cells ◽  
Spatiotemporal Information ◽  
Fluorescence Light ◽  
Correlation Process ◽  
Electron Imaging

AbstractCorrelative light and electron microscopy (CLEM) combines the strengths of both light and electron imaging modalities and enables linking of biological spatiotemporal information from live-cell fluorescence light microscopy (fLM) to high-resolution cellular ultra-structures from cryo-electron microscopy and tomography (cryoEM/ET). This has been previously achieved by using fLM signals to localize the regions of interest under cryogenic conditions. The correlation process, however, is often tedious and time-consuming with low throughput and limited accuracy, because multiple correlation steps at different length scales are largely carried out manually. Here, we present an experimental workflow, AutoCLEM, which overcomes the existing limitations and improves the performance and throughput of CLEM methods, and associated software. The AutoCLEM system encompasses a high-speed confocal live-cell imaging module to acquire an automated fLM grid atlas that is linked to the cryoEM grid atlas, followed by cryofLM imaging after freezing. The fLM coordinates of the targeted areas are automatically converted to cryoEM/ET and refined using fluorescent fiducial beads. This AutoCLEM workflow significantly accelerates the correlation efficiency between live-cell fluorescence imaging and cryoEM/ET structural analysis, as demonstrated by visualizing human immunodeficiency virus type 1 (HIV-1) interacting with host cells.

scholarly journals Reovirus Forms Neo-Organelles for Progeny Particle Assembly within Reorganized Cell Membranes

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Isabel Fernández de Castro ◽  
Paula F. Zamora ◽  
Laura Ooms ◽  
José Jesús Fernández ◽  
Caroline M.-H. Lai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Viral Replication ◽  
Cell Membranes ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Pharmacological Intervention ◽  
Genome Replication ◽  
Particle Assembly ◽  
Intermediate Compartment

ABSTRACTMost viruses that replicate in the cytoplasm of host cells form neo-organelles that serve as sites of viral genome replication and particle assembly. These highly specialized structures concentrate viral replication proteins and nucleic acids, prevent the activation of cell-intrinsic defenses, and coordinate the release of progeny particles. Despite the importance of inclusion complexes in viral replication, there are key gaps in the knowledge of how these organelles form and mediate their functions. Reoviruses are nonenveloped, double-stranded RNA (dsRNA) viruses that serve as tractable experimental models for studies of dsRNA virus replication and pathogenesis. Following reovirus entry into cells, replication occurs in large cytoplasmic structures termed inclusions that fill with progeny virions. Reovirus inclusions are nucleated by viral nonstructural proteins, which in turn recruit viral structural proteins for genome replication and particle assembly. Components of reovirus inclusions are poorly understood, but these structures are generally thought to be devoid of membranes. We used transmission electron microscopy and three-dimensional image reconstructions to visualize reovirus inclusions in infected cells. These studies revealed that reovirus inclusions form within a membranous network. Viral inclusions contain filled and empty viral particles and microtubules and appose mitochondria and rough endoplasmic reticulum (RER). Immunofluorescence confocal microscopy analysis demonstrated that markers of the ER and ER-Golgi intermediate compartment (ERGIC) codistribute with inclusions during infection, as does dsRNA. dsRNA colocalizes with the viral protein σNS and an ERGIC marker inside inclusions. These findings suggest that cell membranes within reovirus inclusions form a scaffold to coordinate viral replication and assembly.IMPORTANCEViruses alter the architecture of host cells to form an intracellular environment conducive to viral replication. This step in viral infection requires the concerted action of viral and host components and is potentially vulnerable to pharmacological intervention. Reoviruses form large cytoplasmic replication sites called inclusions, which have been described as membrane-free structures. Despite the importance of inclusions in the reovirus replication cycle, little is known about their formation and composition. We used light and electron microscopy to demonstrate that reovirus inclusions are membrane-containing structures and that the endoplasmic reticulum (ER) and the ER-Golgi intermediate compartment interact closely with these viral organelles. These findings enhance our understanding of the cellular machinery usurped by viruses to form inclusion organelles and complete an infectious cycle. This information, in turn, may foster the development of antiviral drugs that impede this essential viral replication step.

A correlated light and electron microscopic study of symbiotic growth and differentiation in Pisum sativum root nodules

1976 ◽  
Vol 54 (18) ◽  
pp. 2163-2186 ◽  
Author(s):  
William Newcomb
Keyword(s):  
Electron Microscopy ◽  
Pisum Sativum ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Light And Electron Microscopy ◽  
Infection Thread ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Garden Pea ◽  
Host Cytoplasm

Plants of the garden pea Pisum sativum cv. Little Marvel were grown in aeroponic culture to facilitate observations and microscopy and were inoculated with Rhizobium leguminosarum, and nodules were sampled at five weekly intervals for light and electron microscopy. The invasion of the cortical cells by the infection thread, the structure of the infection thread, and the release of bacteria from it into the host cytoplasm and the subsequent symbiotic growth and differentiation of the two organisms are described in detail. The fine structure of the nodule is correlated with light microscopic observations and morphogenesis. A restriction in the use of the term 'vesicle' is proposed because of the current multiple and confusing usage of the term. The loss of the nodule meristem and its morphogenetic significance are discussed.

Ultrastructural and immunological demonstration of the nodulation of the European Alnus glutinosa (L.) Gaertn. host plant by the North-American Alnus crispa var. mollis Fern, root nodule endophyte

1977 ◽  
Vol 23 (11) ◽  
pp. 1529-1547 ◽  
Author(s):  
M. Lalonde ◽  
A. Quispel
Keyword(s):  
Host Plant ◽  
North American ◽  
Root Nodule ◽  
Light And Electron Microscopy ◽  
Root Hairs ◽  
Alnus Glutinosa ◽  
Bacterial Cells ◽  
Cortical Cells ◽  
Alnus Crispa ◽  
The North

The inoculation of the European Alnus glutinosa (L.) Gaertn. host plant by a crushed-nodule inoculum, prepared with the North-American Alnus crispa var. mollis Fern, root nodule, was successful. Fluorescein- and ferritin-labelled antibodies, specific against the A. crispa var. mollis root nodule endophyte (Lalonde et al. 1975), demonstrated the identity of this endophyte in the resulting nodules. The nodulation process of this abnormal host–endophyte system was studied by light and electron microscopy. An excretion of host blebs containing electron-dense polysaccharide material, resulting in the formation of exo-encapsulation threads containing presumptive endophytic bacterial cells, was associated with deformed root hairs. Originating from an exoen-capsulation thread, the endophyte penetrates the root hair cell and then migrates as a hypha toward the cortical cells of the root. Its migration in the cortical cells of the primary nodule results in the induction of a lateral root which develops as the true nodule. The ultrastructure of the A. crispa var. mollis endophyte developing in the primary and true nodule of the abnormal A. glutinosa host was similar to the one induced inside its normal A. crispa var. mollis host. The actinomycetal intruder was a branched and septate hypha able to produce septate vesicles. The endophyte was always encapsulated in an electron-dense polysaccharide material surrounded by a host plasma membrane envelope. However, in this abnormal host–endophyte system, the number of primary nodules formed per root system was drastically reduced, and their appearance was delayed by 1 to 2 weeks. The delayed nodules were effective in fixing nitrogen and able to support satisfactory plant growth in a nitrogen-free medium.

Resistant responses in juvenile seedlings of Pinus densiflora (Japanese red pine) inoculated with Endocronartium harknessii

1989 ◽  
Vol 67 (12) ◽  
pp. 3545-3552 ◽  
Author(s):  
A. A. Hopkin ◽  
P. V. Blenis ◽  
Y. Hiratsuka
Keyword(s):  
Host Cell ◽  
Vascular Tissue ◽  
Pinus Densiflora ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Cortical Cells ◽  
Host Cell Death ◽  
Endocronartium Harknessii ◽  
Infected Cells ◽  
Endodermal Cells

Hypocotyls of Pinus densiflora, a species known to be resistant to western gall rust, were inoculated with Endocronartium harknessii and examined by light and electron microscopy. Host cells, when initially infected, were apparently unaffected, as were the haustoria within them. Seedlings were observed to respond to infection in two ways. In the first type of response, infected cells showed signs of necrosis by 9 days after inoculation, although infecting haustoria appeared normal. By 18 days, most cortical cells in the centre of the infected region were necrotic, as were the haustoria within them. Infected cells at the colony margin still appeared healthy, indicating that host cell necrosis lagged behind infection and only occurred after the haustorium was established. Four weeks after inoculation, a ring of suberized and lignified endodermal cells separated the infected cortex from the uninfected vascular tissue and appeared to prevent further inward growth of the fungus. The second response type involved production of encapsulations around haustoria. Encapsulations appeared to have formed after haustoria senescence and were eventually followed by host cell death.

Root hair infection process and myconodule formation on Alnus incana by Penicillium nodositatum

1994 ◽  
Vol 72 (7) ◽  
pp. 955-962 ◽  
Author(s):  
Jeanine Sequerra ◽  
André Capellano ◽  
Monique Faure-Raynard ◽  
André Moiroud
Keyword(s):  
Root Hair ◽  
Light And Electron Microscopy ◽  
Root Hairs ◽  
Infection Process ◽  
Initial Contact ◽  
Alnus Incana ◽  
Cortical Cells ◽  
Infected Root ◽  
Root Hair Infection ◽  
Polysaccharide Matrix

Penicillium nodositatum infects the roots of alder trees and induces the formation of structures called myconodules, which are similar to young actinorhizae. Root infection of Alnus incana by P. nodositatum as well as myconodule development were studied by light and electron microscopy and observations were compared with those described for the infection by Frankia spp. We have established an obvious homology between the early steps of the infection caused by both microorganisms. The presence of the fungus near the roots induces deformation of root hairs. The infection site is probably localized in a folding of a deformed hair. As soon as hyphae penetrate into the hair, they become enclosed in a polysaccharide matrix. Initially, P. nodositatum colonizes a region near the infected root hair that may correspond to a slightly developed prenodule. Then a nodular primordium is initiated at some distance from the initial contact and the new nodular cortex is invaded by the fungus. The zone of infection is limited to the cortical cells by a barrier of tannins. Myconodules remain small and unilobed and have an outer morphology similar to that of an incompatible Frankia nodule. Key words: Alnus, myconodule formation, Penicillium, root hair infection.

Microscopic Examination of Chilling Injury Symptoms in Ethanol-treated Cucumber Seedling Roots

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 454e-454
Author(s):  
Windy A. Boyd ◽  
Paul H. Jennings
Keyword(s):  
Electron Microscopy ◽  
Cell Walls ◽  
Chilling Injury ◽  
Light And Electron Microscopy ◽  
Ethanol Solution ◽  
Root Tip ◽  
Cucumber Seedling ◽  
Cortical Cells ◽  
Before And After ◽  
Seedling Roots

Cucumber seedlings were germinated for 24 h at 25 °C and half were immersed in a 500 mM ethanol solution for 2 h. After rinsing, seedlings were chilled for 96 h at 2 °C. Control and ethanol-treated samples were taken for light and electron microscopy immediately before and after chilling, and after re-warming for 24 and 72 h. Preliminary experiments revealed visual chilling symptoms such as pinching of the root in a region just above the root tip. This region was excised under a microscope, fixed, and mounted for microscopic observations. The cortical cells of ethanol-treated seedlings before chilling appeared to be irregular in shape with irregular edges, and some epidermal damage was evident. Chilling caused much more epidermal damage in the control seedlings when compared to the ethanol-treated seedlings. After chilling, cortical cells in the control seedlings were observed to be irregularly shaped while those treated with ethanol had round cells. Upon re-warming, control seedlings exhibited increasing epidermal damage with broken cell walls, while ethanol-treated seedlings exhibited more differentiation in the stele.

scholarly journals Exposure to stressors and antimicrobials induces cell-autonomous ultrastructural heterogeneity of an intracellular bacterial pathogen

2020 ◽  
Author(s):  
Marc Schulte ◽  
Michael Hensel ◽  
Katarzyna Miskiewicz
Keyword(s):  
Electron Microscopy ◽  
Salmonella Enterica ◽  
Bacterial Pathogens ◽  
Single Cells ◽  
Physiological State ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Mammalian Host ◽  
Proliferating Cells ◽  
Experimental Conditions

AbstractDespite being clonal, bacterial pathogens show a remarkable physiological heterogeneity during infection of host and within host cells. This diversity is reflected by distinct ultrastructural morphotypes in transmission electron microscopy (TEM). Gram-negative bacteria visualized at high resolution by TEM show a rather simple composition of cytoplasm with a centrally located nucleoid and large number of ribosomes. The cytoplasm is separated from the external environment by inner and outer membranes. In this study, we show that individual cells of Salmonella enterica serovar Typhimurium (STM) are ultrastructural divergent in standard culture conditions, as well as during their intracellular lifestyle in mammalian host cells. STM can basically be discriminated into two morphotypes based on the criterion of cytoplasmic density. We identified environmental conditions which affect cytoplasmic densities. Using chemical treatments and defined mutant strains, we were able to link the occurrence of an electron-dense type to oxidative stress and other noxes. Furthermore, ultrastructural analyses of STM during infection and fluorescence reporter analyses for cell viability were combined in a correlative light and electron microscopy approach. We provide evidence that two newly characterized ultrastructural types with lucent or dense cytoplasm represent viable cells. Moreover, the presence of electron-dense types is stress related and can be experimentally induced only when amino acids are available in the environment. This study sheds more light on diversities between individual bacteria in populations and possible physiological meanings like a stress response to explain the diversities discussed.ImportanceBacterial pathogens show a remarkable resilience to adverse conditions during infection. Although being genetically identical, a clonal population may contain dead, dormant, slowly as well as rapidly proliferating cells. The physiological state of individual cells in a population may be analyzed by fluorescent probes or reporters. In contrast, reliable markers to interrogate single cells regarding viability, response to environmental cues, and exposure to antimicrobial compounds are sparse for ultrastructural approaches. For intracellular Salmonella enterica we observed distinct ultrastructural morphotypes. Using defined experimental conditions, these morphotypes were linked to reactions of bacteria to stressors or antimicrobials. The parameters defined here provide criteria for the interpretation of bacterial heterogeneity on the ultrastructural level.

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