ELECTRON MICROSCOPIC OBSERVATIONS OF THE DEVELOPMENT OF COXIELLA BURNETII IN THE CHICK YOLK SAC

Current and past strategies for bacterial culture in clinical microbiology

A pure bacterial culture remains essential for the study of its virulence, its antibiotic susceptibility, and its genome sequence in order to facilitate the understanding and treatment of caused diseases. The first culture conditions empirically varied incubation time, nutrients, atmosphere, and temperature; culture was then gradually abandoned in favor of molecular methods. The rebirth of culture in clinical microbiology was prompted by microbiologists specializing in intracellular bacteria. The shell vial procedure allowed the culture of new species of Rickettsia. The design of axenic media for growing fastidious bacteria such as Tropheryma whipplei and Coxiella burnetii and the ability of amoebal coculture to discover new bacteria constituted major advances. Strong efforts associating optimized culture media, detection methods, and a microaerophilic atmosphere allowed a dramatic decrease of the time of Mycobacterium tuberculosis culture. The use of a new versatile medium allowed an extension of the repertoire of archaea. Finally, to optimize the culture of anaerobes in routine bacteriology laboratories, the addition of antioxidants in culture media under an aerobic atmosphere allowed the growth of strictly anaerobic species. Nevertheless, among usual bacterial pathogens, the development of axenic media for the culture of Treponema pallidum or Mycobacterium leprae remains an important challenge that the patience and innovations of cultivators will enable them to overcome.

Coxiella burnetii exhibits morphological change and delays phagolysosomal fusion after internalization by J774A.1 cells

Coxiella burnetii, the etiological agent of Q fever, is an obligate intracellular bacterium proliferating within the harsh environment of the phagolysosome. Mechanisms controlling trafficking to, and survival of pathogens within, the phagolysosome are unknown. Two distinct morphological variants have been implicated as playing a role in C. burnetii survival. The dormant small-cell variant (SCV) is resistant to extracellular stresses and the more metabolically active large-cell variant (LCV) is sensitive to environmental stresses. To document changes in the ratio of SCVs to LCVs in response to environment, a protein specific to SCV, ScvA, was quantitated. During the first 2 h after internalization of C. burnetii by J774A.1 cells, the level of ScvA decreased, indicating a change from a population containing primarily SCVs to one containing primarily LCVs. In vitro experiments showed that 2 h of incubation at pH 5.5 caused a significant decrease in ScvA in contrast to incubation at pH 4.5. Measuring in vitro internalization of [(35)S]methionine-[(35)S]cysteine in response to pH, we found the uptake to be optimal at pH 5.5. To explore the possibility that after uptake C. burnetii was able to delay phagolysosomal fusion, we used thorium dioxide and acid phosphatase to label phagolysosomes during infection of J774A.1 cells. We determined that viable C. burnetii was able to delay phagolysosomal fusion. This is the first time that a delay in phagolysosomal fusion has been shown to be a part of the infection process of this pathogenic microorganism.

FINE STRUCTURE OF RICKETTSIA QUINTANA CULTIVATED IN VITRO AND IN THE LOUSE

Ito, Susumu (Harvard Medical School, Boston, Mass.), and J. W. Vinson. Fine structure of Rickettsia quintana cultivated in vitro and in the louse. J. Bacteriol. 89:481-495. 1965.-Usually rod-shaped, Rickettsia quintana cells measure about 0.2 to 0.5 mu wide and up to 1.6 mu long. The rickettsiae have both an outer cell wall, about 80 A thick, and a plasma membrane, about 70 A thick, each of which is trilaminar. Occasional vesicular invaginations of the plasma membrane occur. The nuclear material, distributed in irregular zones throughout the cytoplasm, appears as a loose network of fine fibrils when postfixed with uranyl acetate and as thick strands or clumps after routine OsO(4) fixation. The cytoplasm is densely packed with numerous granules, presumably ribosomes, about 150 A in diameter. Histochemical studies revealed the presence of both ribonucleic and deoxyribonucleic acids. During binary fission, a constricting furrow is formed by the cell wall and plasmalemma. No difference in fine structure was observed between R. quintana propagated on cell-free media and in the louse.

Some contributions of electron microscopy to the study of the rickettsiae

Electron microscopy has provided valuable insights into the study of rickettsiae as intracellular parasites from several important perspectives. This tool has allowed researchers to delineate the fine structural features of these organisms and to show that they truly resemble free-living bacteria. Furthermore, it has been shown that there are subtle, but distinct differences in the outer envelope structure of some members of the genus Rickettsia that may explain reported differences in tinctorial properties and in their sensitivity to certain antibiotics. With Coxiella burnetii, electron microscopy has helped significantly in the characterization of the pleomorphic nature of the organism including formation of terminal bodies that resemble endospores of gram-positive bacteria. Electron microsxopy has also helped to define the relationship of the rickettsiae to their host cells. For example, ultrastructural analysis can reveal whether organisms exist free within the cytoplasm or nucleus (members of the genus Rickettsia), or whether they are bound by a phagosomal or phagolysosomal membrane (Ehrlichia and Coxiella). Finally, although all rickettsiae eventually destroy their host cell, it has been shown through transmission electron microscopy that this destruction might be mediated by different mechanisms that are specific for different rickettsial species.

Localization of DNA in Coxiella burnetii by post-embedding immunoelectron microscopy

The deoxyribonucleic acid of Coxiella burnetii was detected with monoclonal antibodies against single-stranded and double-stranded DNA by post-embedding immunoelectron microscopy. The antibody labeled the nucleoid of the spore, the small cell variant (SCV), and the large cell variant (LCV). The DNA was segregated completely in both the spore and the mother cell. At the terminal stage of development of the spore, the loss of nuclear morphology in the mother cell was related to the reduction in the labeling of the nucleoid. The mother cell was therefore killed for the development and release of the spore.

Isolation of a protein antigen from Coxiella burnetii

Antigens prepared from Coxiella burnetti, strain Frankfurt, phase II, propagated in persistently infected Buffalo Green Monkey (BGM) cell cultures were purified by guanidinium hydrochloride treatment and chloroform/methanol extraction. By ELISA analysis, chloroform/methanol residues (CMR) proved to be free of host cell antigens. The CMR were sensitive to trypsin, pronase E and proteinase K, as determined by absorption-kinetics of CMR suspensions at 600 nm and release of protein. Coomassie blue stained SDS polyacrylamide gels of proteinase hydrolysates from CMR revealed only a single component of apparently 27,000 D. Silver stained gels, however, showed a second component of apparently 12,000 D. In contrast, from untreated native C. burnetii a large variety of proteins, most of them protease-sensitive, were released by detergents at low temperatures, but the 27,000 D component was only solubilized at 60-100 degrees C. The 27,000 D component was obviously the major protein of CMR as well as of whole cells. Antigenicity of this 27,000 D protein could be demonstrated by agargel precipitation test, ELISA and immunoperoxidase techniques applying antisera raised against whole cells and against the extracted component. The component was also recognized in a dot immunobinding assay by sera from guinea pigs infected with cloned C. burnetii stain Nine Mile, phase I, thus indicating an important role of this antigen in C. burnetii specific immune response.

Sensitivity of Coxiella burnetii peptidoglycan to lysozyme hydrolysis and correlation of sacculus rigidity with peptidoglycan-associated proteins

The protease-resistant proteins associated with the peptidoglycan (PG) of the phase I small-cell variant Coxiella burnetii were either partially released from the PG by boiling the PG-protein complex (PG-PC) in sodium dodecyl sulfate containing 2-mercaptoethanol and EDTA or totally released by 1 N NaOH hydrolysis at 23 degrees C. An 18,300-dalton protein was released from the PG-PC under reducing conditions, whereas 1 N NaOH treatment extracted PG-associated proteins without apparent dissolution of the PG. Purified PG was composed of muramic acid, glucosamine, glutamic acid, alanine, and meso-diaminopimelic acid in a molar ratio of 0.9:0.9:1.0:1.4:1.0. Lysozyme hydrolysis of cell walls, PG-PC, and purified PG caused an increase in reducing groups which correlated with roughly 60 to 100% digestion of disaccharides. There was no significant decrease in turbidity during lysozyme hydrolysis of cell walls and PG-PC; however, hydrolysis of purified PG caused about 90% decrease in turbidity. Approximately 60% of the meso-diaminopimelic acid groups of PG were not susceptible to dinitrophenylation, thus, demonstrating an apparent contribution of PG-associated proteins, rather than cross-linkage between peptides, to sacculus rigidity of cell wall and PG-PC. This association of PG and protease-resistant covalently bound proteins may be important structural and functional determiners of resistance to both environmental conditions and intracellular digestion of C. burnetii by eucaryotic cells.

Q fever and Coxiella burnetii: a model for host-parasite interactions

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Developmental cycle of Coxiella burnetii: structure and morphogenesis of vegetative and sporogenic differentiations

Coxiella burnetii is a gram-variable obligate intracellular bacterium which carries out its development cycle in the phagolysosome of eucaryotic cells. Ultrastructural analysis of C. burnetii, in situ and after Renografin purification, by transmission electron microscopy of lead-stained thin sections has revealed extreme pleomorphism as demonstrated by two morphological cell types, a large cell variant (LCV) and a small cell variant (SCV). Potassium permanganate staining of purified rickettsiae revealed a number of differences in the internal structures of the cell variants. (i) The outer membrane of the sCV and LCV were comparable; however, the underlying dense layer of the SCV was much wider and more prominent than that of the LCV. The periplasmic space of the SCV was not readily visualized, whereas the periplasmic space of the LCV was apparent and resembled that of other gram-negative bacteria. (ii) Complex internal membranous intrusions which appeared to originate from the cytoplasmic membrane were observed in the SCV. The LCV did not harbor an extensive membranous system. (iii) Some LCVs contained a dense body in the periplasmic space. This endogenous structure appeared to arise in one pole of the LCV as an electrondense "cap" formation with the progressive development of a dense body approximately 130 to 170 nm in diameter which was eventually surrounded by a coat of at least four layers. Our observations suggest that the morphogenesis of C. burnetii is comparable, although not identical, to cellular differentiation of endospore formation. A developmental cycle consisting of vegetative and sporogenic differentiation is proposed.

Host-parasite interaction and development of infraforms in chicken embryos infected with Coxiella burnetii via the yolk sac

Two phase I strains of Coxiella burnetii of different virulence were injected into the yolk sacs of chicken embryos, and the yolk sacs and livers were examined at intervals by light, fluorescent, and electron microscopy. The high absorptive and digestive capacities of the yolk endoderm contributed to he entrance of the organisms into endodermal epithelial cells where C. burnetii multiplied. Organisms multiplied not only inside specific vacuoles originating from phagolysosomes but also in the cytoplasm itself. Lysis of the limiting membrane of some phagolysosomes, a normal function of endodermal cells, as well as rupture of vacuoles, provided the release of C. burnetii into the cytoplasm. The C. burnetii strain of greater virulence infected 100% of the endodermal cells, whereas the strain of lesser virulence infected only 60%. Budding of very small particles from the C. burnetii bodies was demonstrated. The particles were regarded as filterable forms of the organism. Despite the enormous multiplication of C. burnetii in the endodermal cells, organisms were only rarely detected in the vitelline blood vessels and liver sinusoids of the embryos. Peculiarities of the infectious process of C. burnetii in chicken embryos and possible mechanisms of limitation of spread of the infection are discussed.

Changes in immunoferritin labeling of Rickettsia tsutsugamushi after serial cultivation in 60Co-irradiated BHK cells

The immunolabeling characteristics of Rickettsia tsutsugamushi (Gilliam strain) were examined by using a purified immunoglobulin G fraction of antibody to R. tsutsugamushi raised in rabbits. Formalin-fixed rickettsiae were reacted with this antibody and then with ferritin-conjugated goat anti-rabbit Fc antibody. R. tsutsugamushi cultivated in yolk sacs was used to raise antibody for this study. When rickettsiae in BHK-21 cells infected from yolk sac seed material were immunoferritin labeled, the binding of ferritin was found to be dense and uniform on the outer surface of the rickettsiae in disrupted host cells. Immunolabeling of purified suspensions of extracellular rickettsiae resulted in the uniform ferritin labeling of the microorganism. Aggregation of these rickettsiae by antibody appeared to depend upon the purity of the pellets. Immunoferritin labeling examined at high magnification revealed ferritin very close to the outer dense leaflet of the outer membrane. On some rickettsiae or on focal sites of others, the labelin; was several ferritin particles thick, suggesting the presence of a thick coating. The immunoferritin labeling of R. tsutsugamushi during successive serial passages in BHK-21 cells revealed decreased labeling with each passage, and by the 10th passage there was no detectable labeling. However, these rickettsiae inoculated back into yolk sacs regained their immunoferritin labeling. R. tsutsugamushi passed back into yolk sacs after four serial propagations in BHK-21 cells regained their labeling on the first passage in yolk sacs. However, rickettsiae from the 20th serial passage in BHK-21 cells required five passages in yolk sacs to reestablish their previous labeling affinity. Rickettsiae which did not label after 20 passages in BHK cells regained some of their labeling characteristics when sonicated. Antibody against rickettsiae cultivated in BHK-21 cells continued labeling rickettsiae even after 9 serial passages in BHK-21 cells.

Studies on rickettsia-like body in Kawasaki disease. Attempts of the isolation and characterization

Rickettsia-like bodies were reportedly found in biopsies of the skin and lymph nodes from half the number of patients with Kawasaki's disease. In our present work, these microbodies were isolated from the peripheral whole blood of a patient with Kawasaki's disease (MLNS) through passage of guinea pigs and yolk sac culture. However, the isolated strains disappeared spontaneously during their stores at -80 degrees C for two weeks.

Electron microscopic study on the interaction between normal guinea pig peritoneal macrophages and Coxiella burnetii

An electron microscopic study was conducted to explore the interaction between normal guinea pig peritoneal macrophages and phase I and II Coxeilla burnetii previously treated with either normal or immune serum. A comparison was made on the efficiency of phagocytosis and subsequent killing of rickettsiae by macrophages. Both phases of rickettsiae previously treated with normal serum multiplied within phagosomes after phagocytosis with resultant destruction of macrophages. In contrast, suspending rickettsiae in immune serum rendered them more susceptible to phagocytosis and potentiated their destruction within macrophages.

Changes in buoyant density relationships of two cell types of Coxiella burneti phase I

Coxiella burneti phase I, purified from a formalin-inactivated yolk-sac vaccine, was separated into two bands of morphologically distinct cell types when subjected to sucrose gradient centrifugation. Recycling of the less dense, rod-shaped cells in unbuffered sucrose gradients (pH 5.5 to 6.0) resulted in the formation of bands having the location and appearance of the original two bands. Recycling of the denser band of larger ovoid-shaped cells yielded a single band, suggesting that the larger cell type arose from the smaller cell. In contrast to vaccine-derived rickettsiae, live, cell culture-propagated phase I organisms formed a single band in unbuffered sucrose gradients, at the same density as the upper band of the vaccine preparation. Centrifugation of cell culture-derived rickettsiae for 26 to 48 h in sucrose gradients of pH 5.5 resulted in the formation of a second band, at the same density as the lower band of the vaccine preparation. This did not occur in gradients of pH 7.0. Treatment of cell culture-propagated rickettsiae with formalin or germicidal ultraviolet radiation induced a total shift of the less dense cell population to a zone of higher density when centrifuged isopycnically in CsC1 gradients. This density change did not occur in sucrose gradients, suggesting a difference in the effect of these treatments on the permeability of the cell membrane to sucrose and CsC1.

Electron microscopy studies of the limiting layers of the rickettsia Coxiella burneti

Surface layers of Coxiella burneti studied at a high resoulution reveal a plasma membrane and an outer surface membrane 6 to 7 nm thick, and a thin, moderately electron-dense intermediate layer associated with the inner surface of the outer membrane of many cells. This layer appears to be unaffected by lysozyme treatment. Ruthenium red staining was used to delineate a layer of filamentous material external to the outer membrane; this fuzzy layer has a mean thickness of 20 nm and is not often seen on the surface of cells prepared by conventional means. Both antigenic phase I and II cells show a ruthenium red-binding surface layer. It is suggested that this fuzzy layer may be, among other possibilities, a highly branched mucopolysaccharide.

Ultrastructural study of Pierce's disease bacterium in grape xylem tissue

The rod-shaped rickettsia-like bacteria of Pierce's disease measure about 0.25 to 0.50 mum in diameter and 1.0 to 4.0 mum long. The bacteria have a cell wall consisting of a trilaminar outer membrane and two intermediate low-density layers separated by a dense intermediate layer. A trilaminar cytoplasmic membrane is also present, resulting in a total wall complex thickness of 25 to 40 nm. A periodic infolding of the outer membrane and intermediate layers of the wall give the wall surface a ridged apperance. The ridges appear to go around the long axis of the cell, possibly in the form of spirals. Ribosomes and nuclear regions with easily visible deoxyribonucleic acid strands and clumps are distributed throughout the cytoplasm. Binary fission, during which the cell wall and cytoplasmic membrane folded inward to partition the cell, was observed. In the xylem of infected grapes, the bacteria are either distributed evenly throughout the lumen of the xylem vessel or appressed along the inner surface of the vessel walls in an electron-lucent matrix.

Isolation and characterization of two cell types of Coxiella burneti phase I

Two morphologically distinct cell types of Coxiella burneti phase I have been separated on the basis of unique buoyant densities. When centrifuged to equilibrium in cesium chloride or density gradients of sucrose or Renografin, the cells band in two zones. Electron micrographs of ultrathin sections of the two cesium chloride-separated cell types indicate a considerable number of morphological differences. The lower-density cells are small, compact, and rodshaped and have very dense nucleoids. The cell type of highest density is larger, rounded, and more pleomorphic, and the nucleoid filaments are more dispersed. The two cell types are nearly identical in sedimentation rates, and both infect chick yolk sac cells and are lethal to chick embryos. They convert to a mixture of cell types when cultured separately. Treatment with Formalin induces all cells to band at the same position when centrifuged to equilibrium in cesium chloride. The cell type variance was found to be independent of the antigenic phase phenomenon of C. burneti.

Fine structure of Rickettsia canada in tissues of Dermacentor andersoni Stiles

Preliminary observations on growth and developmental fine structure of Rickettsia canada in various organs and tissues of the hard tick, Dermacentor andersoni Stiles, are reported. R. canada is typically rod-shaped, being delimited with a three-layered wall having a velvety coating adsorbed to its exterior surface. A finely reticulated cytoplasmic matrix containing prominent ribosomes is delimited with a three-layered unit membrane. Average length and width of these organisms are 1.6 by 0.4 mum. Although R. canada produces a generalized infection in D. andersoni, hypodermal and muscle tissues experience heaviest growth. Three morphologically distinct rickettsial forms were observed in individual hypodermal cells: (i) typical growth forms with a finely reticulated cytoplasmic matrix and distinct ribosomes; (ii) atypical forms with lightly to densely staining cytoplasm and a coagulated appearance in which ribosomes cannot be distinguished from the matrix; and (iii) forms with crystalline bodies that have a striated to beaded lattice structure and, at times, a fibrillar body in the cytoplasm as well. Occasional finger-like to irregular invaginations of the plasma membrane are noted. Intranuclear growth was demonstrated by electron microscopy in gut epithelial cells only. Growth and development of R. canada were manifest in all tissues examined.

Spermatocyte granules in Drosophila melanogaster

Granular inclusions are found in testes from a cn bw stock of Drosophila melanogaster, and maternally derived lines, such as SD. In late larval and early pupal stages, these granules show a polarized distribution within primary spermatocytes corresponding to the polarity basic to the type of meiotic drive where certain homologues reach that pole of the spermatocyte leading to functional sperm. In adult males, the granules are found in intercellular patches in the testes. Electron microscopy shows the spermatocyte granules to be spheroids of about 0.7 μ; dividing, or double forms resulting from division, are about 1.8 μ long. They contain numbers of ribosome-like particles and fine strands presumed to be DNA. The acridine orange test for nucleic acids was positive. Each granule is surrounded by two layers of unit membrane and a third such membrane envelopes the individual or the pair of granules, as the case may be. The third membrane layer (and additional membranes sometimes seen) is thought to be due to entrance of the granules into the host cell through the cisternae of the endoplasmic reticulum. Transmission of the granules is strictly maternal and independent of chromosome constitution. Transmission by contagion was not found. Spermatocyte granules are not requisite to the effectiveness of the SD meiotic drive system, which regularly carries them. A slightly lowered fertility of females carrying the granules was found but no similar effect is produced in males. The evidence suggests that they are parasitic organisms, probably Rickettsiae.

Intranuclear growth of Rickettsia rickettsii

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Electron microscopic observations of Coxiella burnetii in the guinea pig

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The cell wall of Rickettsia mooseri. I. Morphology and chemical composition

Cell walls prepared by mechanically disrupting intact Rickettsia mooseri (R. typhi) were examined in an electron microscope and analyzed chemically. Electron micrographs of metal-shadowed and negatively stained rickettsial cell walls revealed no significant differences, except for smaller size, from bacterial cell walls prepared in a similar manner. The chemical composition was complex, and resembled that of gram-negative bacterial cell walls more closely than that of gram-positive bacterial cell walls. R. mooseri cell walls contained the sugars, glucose, galactose, and glucuronic acid, the amino sugars, glucosamine, and muramic acid, and at least 15 amino acids. Diaminopimelic acid, a compound hitherto found only in bacteria and blue-green algae, was demonstrated in rickettsiae for the first time. Teichoic acids were not detected. The compounds identified accounted for about 70% of the dry weight of the cell walls.

Fine structure of Haemobartonella muris as compared with Eperythrozoon coccoides and Mycoplasma pulmonis

Tanaka, H. (The Rockefeller University, New York, N.Y.), W. T. Hall, J. B. Sheffield, and D. H. Moore. Fine structure of Haemobartonella muris as compared with Eperythrozoon coccoides and Mycoplasma pulmonis. J. Bacteriol. 90:1735-1749. 1965.-Thin sections of filterable hemolytic anemia agent of rat, now identified as Haemobartonella muris, revealed (i) that the agent is spherical or ellipsoidal and 350 to 700 mmu in size, (ii) that it has a single limiting membrane enclosing granules and some filaments (neither cell wall nor nucleoid was found), and (iii) that it is found preferentially at the surface and sometimes within the cytoplasmic vacuoles of erythrocytes in the circulating blood and bone marrow, and multiplies there through binary fission. No specific structure suggestive of motility was found. From the morphological point of view, Eperythrozoon coccoides was found to be very similar to H. muris, whereas Mycoplasma pulmonis, also covered with a single limiting membrane, differs in its pleomorphism and multiplication. These and some other microorganisms taxonomically between bacteria and viruses were compared morphologically, and their possible classification is discussed.