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Category: Microbial Genetics and Molecular Biology
Developmental Cycle of Coxiella burnetii, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818166/9781555811587_Chap21-1.gif /docserver/preview/fulltext/10.1128/9781555818166/9781555811587_Chap21-2.gifAbstract:
Recent advances in the cloning of variant specific proteins has led to a new appreciation of the Coxiella developmental cycle. This chapter summarizes the current state of research in this area and draws upon several recent reviews to present a more defined and testable model of development for this unusual pathogen. The moderate relatedness of Coxiella and Legionella, revealed by 16S rRNA comparison, has proven consistent when sesuch as CbMveral cloned proteins, ip and LpMip, were compared and may prove valuable in understanding the similarities between C. burnetii and Legionella interactions with host cells. The first class of proteins that was identified consisted of basic DNA binding proteins. Heinzen and coworkers provide both single-and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of small-cell variants (SCV) and large-cell variants (LCV) proteins, noting several differences beyond PI, Hql, ScvA, EF-Ts, and EF-Tu. One of the observations that appear to distinguish a C. burnetii developmental cycle from that of Chlamydia is that a mixture of SCV and LCV appears in all vacuoles, whether newly occupied with a few organisms or containing hundreds of organisms. There are superficial similarities between the developmental cycles of C. burnetii and C. trachomatis, since both are obligate intracellular bacterial pathogens that undergo an infectious cycle inside a membrane-bound vacuole. Cellular differentiation in prokaryotes is an adaptive response that involves alterations in gene expression.
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Transmission electron micrograph of bacteria in a vacuole and separated into SCV and LCV. (A) Persistently infected L929 cells were prepared for ТЕМ. Note a membrane-bound vacuole with multiple C. burnetii cells with pleo-morphic morphology, including large cells with diffuse nucleoids (LCV) and small cells with compact nucleoids (SCV). Purified ? burnetii cells were separated into LCV (B) and SCV (C) by cesium chloride equilibrium gradient centrifugation. Bars, 1 μm.
Transmission electron micrograph of bacteria in a vacuole and separated into SCV and LCV. (A) Persistently infected L929 cells were prepared for ТЕМ. Note a membrane-bound vacuole with multiple C. burnetii cells with pleo-morphic morphology, including large cells with diffuse nucleoids (LCV) and small cells with compact nucleoids (SCV). Purified ? burnetii cells were separated into LCV (B) and SCV (C) by cesium chloride equilibrium gradient centrifugation. Bars, 1 μm.
Differential protein expression or ? bumetii proteins detected with monoclonal antibodies. LCV and SCV were separated by cesium chloride equilibrium gradient centrifugation, and proteins were subsequently separated by SDS-PAGE. Monoclonal antibodies specific for each antigen were reacted on Western blots. (A) Monoclonal antibody specific for Com-1 (27 kDa); (B) monoclonal antibody specific for CbMip (25 kDa); (C) monoclonal antibody specific for EF-Ts (32 kDa); (D) monoclonal antibody specific for EF-Tu (45 kDa).
Differential protein expression or ? bumetii proteins detected with monoclonal antibodies. LCV and SCV were separated by cesium chloride equilibrium gradient centrifugation, and proteins were subsequently separated by SDS-PAGE. Monoclonal antibodies specific for each antigen were reacted on Western blots. (A) Monoclonal antibody specific for Com-1 (27 kDa); (B) monoclonal antibody specific for CbMip (25 kDa); (C) monoclonal antibody specific for EF-Ts (32 kDa); (D) monoclonal antibody specific for EF-Tu (45 kDa).
Surface-labeled proteins. LCV and SCV were surface iodinated with Iodogen beads, and proteins were separated by SDS-PAGE followed by auto-radiographic detection of labeled proteins. The major outer membrane protein, PI, is identified. An apparent SVC upregulated surface protein at ∼34 kDa is noted.
Surface-labeled proteins. LCV and SCV were surface iodinated with Iodogen beads, and proteins were separated by SDS-PAGE followed by auto-radiographic detection of labeled proteins. The major outer membrane protein, PI, is identified. An apparent SVC upregulated surface protein at ∼34 kDa is noted.
Model of LCV, SCV, SDC, and SLP. A working model of C. burnetii developmental stages derived from studies summarized in this review. A single infected cell is represented containing a phagolysosome with all four forms. SLP have only been observed infrequently. The ability of each form to develop into one of the alternate forms is unconfirmed. The functional properties assigned to each form and the level of expression of specific proteins is indicated for high (↑↑), medium (↑), relatively low (↓), and not detected (ND).
Model of LCV, SCV, SDC, and SLP. A working model of C. burnetii developmental stages derived from studies summarized in this review. A single infected cell is represented containing a phagolysosome with all four forms. SLP have only been observed infrequently. The ability of each form to develop into one of the alternate forms is unconfirmed. The functional properties assigned to each form and the level of expression of specific proteins is indicated for high (↑↑), medium (↑), relatively low (↓), and not detected (ND).