Studies of the Penetration of Bdellovibrio into Host Cells

1971 ◽  
Vol 29 ◽  
pp. 336-337
Author(s):  
Dinah Abram ◽  
David Chou
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Cell Wall ◽  
Pseudomonas Fluorescens ◽  
Host Cell ◽  
Host Cells ◽  
Sequence Of Events ◽  
Host Cell Wall ◽  
Host Parasite ◽  
Infectious Cycle

The sequence of events in the infectious cycle of the endoparasite Bdello-vibrio bacteriovorus, from its attachment to the host surface to the release of progeny from lysed host are well established. However, the mechanisms involved in the parasite entry through a pore in the host cell wall into its periplasm have been topics for speculations but are not fully understood.Escherichia coli, Pseudomonas fluorescens and Spirillum serpens were infected by several Bdellovibrio strains (109, D and 6-5-S) in mixtures containing 109 to 1010 host cells/ml and host-parasite in ratios of 1:2 to 1:3, and were incubated at 30 C with shaking for 4 hr. At intervals specimens were prepared for electron microscopy and wet mounts were examined by phase optics.

Host – parasite relationships between the fungus Leptosphaerulina crassiasca and peanut

1992 ◽  
Vol 70 (9) ◽  
pp. 1724-1733 ◽  
Author(s):  
Mei-Lee Wu ◽  
Richard T. Hanlin
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Germ Tube ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Detached Leaves ◽  
Host Cell Wall ◽  
Host Parasite ◽  
Germ Tubes ◽  
Infection Hypha

The mode of penetration and infection of the peanut leaf by Leptosphaerulina crassiasca were studied by means of light and electron microscopy. The attachment of the multicellular ascospores to the leaf surface was by a mucilagenous sheath that covered the ascospores at maturity. This sheath expanded rapidly in moisture and it extended along the germ tube as it elongated. Two types of germ tubes appeared to be formed, a short one and a relatively long one. Short germ tubes were not delimited by septa, and they penetrated the cuticle and host epidermal cell wall directly without appressorium formation. Penetration occurred 2–6 h after inoculation. The wall was breached by a relatively broad infection hypha that expanded in width inside the host cell wall. The lack of mechanical rupture at the infection site indicated that penetration may involve enzymatic activity. Intracellular hyphae were present in the epidermal cells, but only intercellular hyphae occurred in the palisade and spongy mesophyll tissues. The intercellular hyphae were frequently appressed to the outer surface of the host cell wall. Infected areas rarely exceeded 1 mm in diameter, and they were only sparsely colonized by hyphae of the pathogen. Host cells in the vicinity of hyphae underwent senescence and death. One to 2 months after inoculation, pseudothecia formed in the dead tissues of detached leaves. In some instances the presence of penetration hyphae by short germ tubes induced the formation of a papilla inside the host cell wall, which either restricted growth of the infection hypha or resulted in the death of the germ tube and the cell from which it arose. Long germ tubes were delimited by simple septa and they terminated in an appressorium; however, details of their behavior were not studied. Key words: Arachis hypogaea, Ascomycotina, Dothideales, leaf scorch, pepper spot.

The Alternaria brassicae – Nectria inventa host–parasite interface

1977 ◽  
Vol 55 (4) ◽  
pp. 448-454 ◽  
Author(s):  
A. Tsuneda ◽  
W. P. Skoropad
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Host Cells ◽  
Alternaria Brassicae ◽  
Adhesive Material ◽  
Large Hole ◽  
Mature Conidium ◽  
Host Cell Wall ◽  
Host Parasite

The Verticillium state of Nectria inventa is a destructive parasite of Alternaria brassicae. Tropic growth of parasite hyphae towards hyphae and conidia of A. brassicae occurs in the vicinity of the host. Upon contact, the parasite hyphae often form appressorium-like bodies on the host cells and produce fibrous adhesive material at the host–parasite interface. Conidia are penetrated more commonly than hyphae. Penetration of the septa in hyphae results in a separation of cells. Penetration of a mature conidium also occurs commonly at a septum. The presence of a large hole in the wall of the host cell and the meshwork of material at the penetration site suggest that enzymatic breakdown of host cell wall occurs. Juvenile conidia are penetrated usually at the basal pore.

Interactions Between Salmonella Typhimurium, Enteropathogenic Escherichia Coli (EPEC), and Host Epithelial Cells

1995 ◽  
Vol 9 (1) ◽  
pp. 31-36 ◽  
Author(s):  
B.B. Finlay
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Salmonella Typhimurium ◽  
Host Cell ◽  
Inositol Phosphate ◽  
Enteric Pathogens ◽  
Host Protein ◽  
Host Cells ◽  
Enteropathogenic Escherichia Coli ◽  
Sequence Of Events

The interactions that occur between pathogenic micro-organisms and their host cells are complex and intimate. We have used two enteric pathogens, Salmonella typhimurium and enteropathogenic Escherichia coli (EPEC), to examine the interactions that occur between these organisms and epithelial cells. Although these are enteric pathogens, the knowledge and techniques developed from these systems may be applied to the study of dental pathogens. Both S. typhimurium and EPEC disrupt epithelial monolayer integrity, although by different mechanisms. Both pathogens cause loss of microvilli and re-arrangement of the underlying host cytoskeleton. Despite these similarities, both organisms send different signals into the host cell. EPEC signal transduction involves generation of intracellular calcium and inositol phosphate fluxes, and activation of host tyrosine kinases that results in tyrosine phosphorylation of a 90-kDa host protein. Bacterial mutants have been identifed that are deficient in signaling to the host. We propose a sequence of events that occur when EPEC interacts with epithelial cells. Once inside a host cell, S. typhimurium remains within a vacuole. To define some of the parameters of the intracellular environment, we constructed genetic fusions of known genes with lacZ, and used these fusions as reporter probes of the intracellular vacuolar environment. We have also begun to examine the bacterial and host cell factors necessary for S. typhimurium to multiply within epithelial cells. We found that this organism triggers the formation of novel tubular lysosomes, and these structures are linked with intracellular replication.

Ultrastructure of compatible and incompatible reactions of sunflower to Plasmopara halstedii

1979 ◽  
Vol 57 (4) ◽  
pp. 315-323 ◽  
Author(s):  
Glenn Wehtje ◽  
Larry J. Littlefield ◽  
David E. Zimmer
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Host Cell ◽  
Epidermal Cell ◽  
Cortical Cell ◽  
Hypersensitive Reaction ◽  
Host Cells ◽  
Plasmopara Halstedii ◽  
Host Cell Wall ◽  
Host Plasma Membrane

Penetration of sunflower, Heliantluis animus, root epidermal cells by zoospores of Plasmopara halstedii is preceded by formation of a papilla on the inner surface of the host cell wall that invaginates the host plasma membrane. Localized degradation and penetration of the host cell wall by the pathogen follow. The invading fungus forms an allantoid primary infection vesicle in the penetrated epidermal cell. The host plasma membrane invaginates around the infection vesicle but its continuity is difficult to follow. Upon exit from the epidermal cell the fungus may grow intercellularly, producing terminal haustorial branches which extend into adjacent host cells. The fungus may grow through one or two cortical cell is after growing from the epidermal cell before it becomes intercellular. Host plasma membrane is not penetrated by haustoria. Intercellular hyphae grow toward the apex of the plant and ramify the seedling tissue. Resistance in an immune cultivar is hypersensitive and is triggered upon contact of the host cell with the encysting zoospore before the host cell wall is penetrated. Degeneration of zoospore cytoplasm accompanies the hypersensitive reaction of the host. Zoospores were often parasitized by bacteria and did not germinate unless penicillin and streptomycin were added to the inoculum suspension.

Ultrastructure of the host–parasite interface in the fern rusts Milesia, Uredinopsis, and Hyalopsora (Pucciniastraceae, Uredinales)

1994 ◽  
Vol 72 (8) ◽  
pp. 1084-1094 ◽  
Author(s):  
R. Berndt ◽  
R. Bauer ◽  
F. Oberwinkler
Keyword(s):  
Cell Wall ◽  
Key Words ◽  
Host Cell ◽  
Electron Density ◽  
Host Cell Wall ◽  
Host Parasite ◽  
Extrahaustorial Matrix

Species of the genera Milesia, Uredinopsis, and Hyalopsora possessed D-haustoria the necks of which were sheathed by an extension of the extrahaustorial matrix. Haustoria of the investigated species of Milesia and Uredinopsis were botryose with a haustorial body that formed wormlike protuberances. The Hyalopsora spp. were characterized by a vesicular haustorium. In the species of Milesia and associated Uredo spp. the haustorial neck was frequently differentiated into areas of variable electron density and structure; in Milesia blechni, Milesia miyabei, and Uredo RB 2537 a second neckband was formed in many haustoria. The penetration channels were usually characterized by short, perpendicularly oriented fibrillar elements that extended into the surrounding host cell wall. The haustoria of Uredinopsis filicina, Hyalopsora polypodii, and Hyalopsora aspidiotus were different from those of the investigated species of Milesia and Uredo. Their necks were accompanied by short extensions of the extrahaustorial matrix and the neck walls stained more or less homogeneously proximal to the neckband. Key words: Milesia, Uredinopsis, Hyalopsora, D-haustoria, ultrastructure, systematics.

Ultrastructure of the host–pathogen interface in Arabidopsis thaliana leaves infected by the downy mildew Hyaloperonospora parasitica

2004 ◽  
Vol 82 (7) ◽  
pp. 1001-1008 ◽  
Author(s):  
C W Mims ◽  
E A Richardson ◽  
B F Holt III ◽  
J L Dangl
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Arabidopsis Thaliana ◽  
High Pressure ◽  
Cell Wall ◽  
Host Cell ◽  
Hyaloperonospora Parasitica ◽  
Transmission Electron ◽  
Host Pathogen ◽  
Host Cell Wall

Transmission electron microscopy was used to examine the host–pathogen interface in Arabidopsis thaliana (L.) Heynh. leaves infected by the biotrophic downy mildew pathogen Hyaloperonospora parasitica (Pers.:Fr.) Constant. Both conventionally fixed as well as high-pressure frozen samples were examined. Excellent preservation of the host–pathogen interface was obtained in many of our high-pressure frozen samples and provided information not available in conventionally fixed samples. Mature haustoria of H. parasitica were distinctly pyriform in shape. A small collar of host cell wall material surrounded the neck of each haustorium near the host cell wall penetration site. The presence of callose in collars was demonstrated using immunogold labeling with a monoclonal antibody specific for (1→3)-β-glucans. The body of each haustorium was ensheathed by an invaginated portion of the invaded host-cell plasma membrane known as the extrahaustorial membrane. Lying between this membrane and the haustorial wall was a layer of electron-dense material known as the extrahaustorial matrix (EHM). The EHM typically was thicker at the distal end of a haustorium than at the proximal end. The surface of the EHM covered by the extrahaustorial membrane was highly irregular in outline. Considerable vesicular activity was observed in association with the extrahaustorial membrane.Key words: transmission electron microscopy, high-pressure freezing, haustoria, Peronospora parasitica.

scholarly journals Histopathological Study of Barley Cultivars Resistant and Susceptible to Rhynchosporium secalis

2000 ◽  
Vol 90 (1) ◽  
pp. 94-102 ◽  
Author(s):  
K. Xi Carisse ◽  
P. A. Burnett ◽  
J. P. Tewari ◽  
M. H. Chen ◽  
T. K. Turkington ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Host Cell ◽  
Significant Negative Correlation ◽  
Seedling Stage ◽  
Histopathological Study ◽  
Rhynchosporium Secalis ◽  
Apparent Difference ◽  
Barley Cultivars ◽  
Host Cell Wall

Differences in the penetration process by Rhynchosporium secalis were compared in resistant and susceptible barley cultivars at the seedling stage. Percent penetration and percent host cell wall alteration (HCWA) differed significantly among cultivars and isolates as revealed by light microscopy. Based on these two variables, the cultivars were statistically separated into two groups that corresponded to their disease reactions. The resistant cultivars, Johnston and CDC Guardian, showed 81.2 to 99.4% HCWA and 0.1 to 20.1% penetration at encounter sites, whereas the susceptible cultivars, Harrington, Argyle, and Manley, had 30.1 to 78.3% HCWA and 31.8 to 81.8% penetration. In the current study, cv. Leduc, which is susceptible at the seedling stage and resistant at the adult stage, showed the same percent HCWA and penetration as did susceptible cultivars. A significant negative correlation (P < 0.01) was found between percent penetration and percent HCWA for cultivars inoculated with two isolates of the pathogen. Isolate 1 was less virulent than isolate 2 with respect to percent penetration and induced significantly fewer HCWA. Scanning electron microscopy showed various shapes of fungal appressoria but no apparent difference in host reaction between resistant and susceptible cultivars. Transmission electron microscopy revealed interactions between the host and pathogen at various stages of penetration. The resistant cv. Johnston responded by producing appositions, as evidenced by a layer of compact osmiophilic material deposited on the inner side of the cell wall. Infection pegs produced by conidia were unable to penetrate the cuticle where an apposition had formed inside. When penetration occurred in the susceptible cv. Argyle, cytoplasmic aggregates and separation of the plasmalemma were visible from the host cell wall, but the layer of compact osmiophilic material was not always present. Data based on light microscopic observations suggested that HCWA may be one of the mechanisms responsible for resistance that is characterized as penetration prevention rather than as a slow rate of mycelial growth after successful penetration. HCWA occurred in response to attempted cuticle penetration, suggesting that HCWA may produce chemical barriers that help to prevent penetration.

THE PHYSIOLOGY OF HOST–PARASITE RELATIONS: XV. FINE STRUCTURE IN RUST-INFECTED WHEAT LEAVES

1965 ◽  
Vol 43 (10) ◽  
pp. 1285-1292 ◽  
Author(s):  
Michael Shaw ◽  
M. S. Manocha
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Susceptible Variety ◽  
Host Cells ◽  
Resistant Variety ◽  
Subcellular Organelles ◽  
Detached Leaves ◽  
Host Cell Wall ◽  
Wheat Leaves ◽  
Host Parasite

Electron microscopy showed that the haustoria of P. graminis tritici on wheat were characterized by numerous mitochondria, an extensive endoplasmic reticulum, densely packed ribosomes, and a well-defined plasma membrane (plasmalemma), which was often invaginated by lomasomes. No evidence was obtained for cytoplasmic connections between the parasite and its host. Many of the haustoria formed on a resistant variety, Khapli, were necrotic but others were closely similar to those formed on a susceptible variety, Little Club. The haustorial necks were surrounded by a collar-like sheath formed by an extension of the host cell wall. The haustoria merely invaginated host protoplasts from which they were separated by granular encapsulations. The latter were apparently secreted mainly by the host and developed faster in Khapli than in Little Club. The presence of haustoria also induced the formation of an extensive, smooth-surfaced endoplasmic reticulum in the host, a contraction and fragmentation of the vacuole, an increase in the volume of the cytoplasm, and, ultimately, the complete degeneration of the host cells. The processes of breakdown of the subcellular organelles in the host were very similar to those which have been observed in uninfected cells in detached leaves senescing on water.

Host–parasite relations in mycoparasite. I. Fine structure of host, parasite, and their interface

1971 ◽  
Vol 49 (9) ◽  
pp. 1677-1681 ◽  
Author(s):  
M. S. Manocha ◽  
K. Y. Lee
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Host Cell ◽  
Higher Plants ◽  
Host Cytoplasm ◽  
Host Cell Wall ◽  
Choanephora Cucurbitarum ◽  
A Cell ◽  
Host Parasite

A mycoparasite, Piptocephalis virginiana, shows resemblance to other fungal parasites of higher plants in the fine structure of hyphae and haustoria. The mode of penetration of the host cell, Choanephora cucurbitarum, probably involves mechanical forces. Although the presence of a cell wall degrading enzyme was not detected by conventional techniques, its role in penetration can not be ruled out. A collar around the haustorial neck is formed as an extension of the host cell wall. No papilla was detected although appressorium was seen during penetration. The young haustorium is enclosed in highly invaginating plasmalemma of the host cell and numerous cisternae of endoplasmic reticulum (ER). Appearance of an electron-dense sheath around the mature haustorium seems to coincide with the disappearance of cisternae of ER from the host cytoplasm in the vicinity of the haustorium. The role of host cytoplasm, particularly of ER, in the development of the sheath is discussed. Extensive accumulation of spherosome-like bodies, containing lipids, is found in haustorium, parasite, and host hypha.

Studies on the haustorium of Castilleja (Scrophulariaceae). II. The endophyte

1973 ◽  
Vol 51 (5) ◽  
pp. 923-931 ◽  
Author(s):  
David R. Dobbins ◽  
Job Kuijt
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Light Microscope ◽  
Cell Walls ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cell Wall ◽  
Dark Staining ◽  
Host Tissues

The portion of the Castilleja haustorium within the host, the endophyte, was examined at the light-and electron-microscopic levels. The endophyte consists of a stalk of lipid-containing cells and digitate cells at its tip. Vessels run the length of the endophyte. There is a harmonious meshing between host cortical cells and those of the endophyte flank, suggesting that penetration is accomplished, in part, by cell dissolution. Crushing of cells also occurs during endophyte invasion as host phloem tissues are severely buckled and cell walls are greatly folded. Some features of digitate cells include dense cytoplasm, an abundance of endoplasmic reticulum, lateral walls that are thickened as well as those on the side adjacent to the host, and an ability to conform to the contours of host tissues. Often digitate cells are divided by very thin walls that are hardly visible under the light microscope. It is suggested that the thick cell walls may function as "free space" in the absorption of materials from the host. Within the endophyte, vessels differentiate and may contain either a finely granular, dark-staining material or a more coarsely granular, light-staining material. The particles of the latter have irregular shapes. Although granular materials are thus carried by some vessels, cells resembling the structurally intermediate "phloeotracheids" were not seen. Connections through the cell wall were not observed between parasite and host; however, within the endophyte plasmodesmata were highly branched and often contained median nodules. Transfer-like cells which have irregularly thickened walls occurred in the endophyte. Host tissues next to digitate cells appeared to be in a degraded state. Invaginations of the plasmalemma were common and small flattened vesicles were formed in some host cells from the disrupted tonoplast. In several instances, the cytoplasm had receded from the host cell wall and a "beaded" material was present in both vacuoles and large vesicles. The host cell wall at times had a very loose fibrillar appearance. Some host tracheids were occluded with a dense and dark-staining material. The xylem strands of the parasite are connected to the host xylem either by cell wall dissolution or by actual penetration of a digitate cell into a host xylary cell. The penetrating cell subsequently differentiates into a vessel member. A summary and general discussion are given to relate the two portions of the haustorium, the upper haustorium and the endophyte. The mass of new information gained in this study leads us to encourage the application of plastic embedding and sectioning techniques to further light-microscope studies on haustoria.

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