Preferred Scientific Name
- Chlamydia trachomatis
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The Chlamydiales, thought to be viruses for a long time, are obligate intracellular bacterial pathogens of higher cells. The chlamydial elementary body (EB) is near the limit of light microscopic visibility with approximately 0.3 µm in diameter, round or occasionally pear-shaped, and contains electron-dense structures. It is the infectious stage of the chlamydial developmental cycle, and functions as a tough ‘spore-like’ body whose purpose is to permit chlamydial survival in the non-supportive environment outside the host cell. The ultrastructure of EB has been extensively studied (Eb et al., 1976; Louis et al., 1980; Matsumoto, 1982; 1988; Rockey et al., 2000; Solof et al., 1982).
The chlamydial reticulate body (RB) is the chlamydial developmental stage during intracellular replication, and it is non-infectious. Typically, the RB has a diameter of approximately 1 µm. The RB is metabolically active, the cytoplasm is rich in ribosomes, which are required for protein synthesis. As the RB begins to differentiate into an EB, sites of re-condensation of nucleic acid appear in its cytoplasm. In the maturing inclusion, chlamydial particles appear to be packed tightly in the inclusion membrane. Development of chlamydiae is highly dependent on nutrient supply and metabolic status of host cells. Nutrient deficiencies such as low glucose levels lead to delayed development and to a few, aberrant chlamydial organisms within the inclusions.
Chlamydial agents, classically have been propagated in the yolk sacs of chicken embryos (Storz, 1971). Cultivation in cell culture is now preferred, and the use of appropriate techniques is important for high-yield culture (Li, et al., 2005). Buffalo Green Monkey Kidney (BGMK) cells support chlamydial replication effectively, particularly when cultivated in Iscove’s Modified Dulbecco’s Medium. EBs are purified by sedimentation, separated from cellular nuclei by low-speed centrifugation, and separated from cell debris by step-gradient centrifugation in a 30% RenoCal-76 50% sucrose step-gradient. Extensive sonication increases yield and infectivity of chlamydial EBs.
Eb F; Orfila J; Lefebvre JF, 1976. Ultrastructural study of the development of the agent of ewe’s abortion. Journal of Ultrastructure Research, 56:177-185.
Li D; Vaglenov A; Kim T; Wang C; Gao D; Kaltenboeck B, 2005. High-yield culture and purification of Chlamydiaceae bacteria. Journal of Microbiological Methods, 61(1):17-24.
Louis C; Nicolas G; Eb F; Lefebvre JF; Orfila J, 1980. Modifications of the envelope of Chlamydia psittaci during its developmental cycle: freeze-fracture study of complementary replicas. Journal of Bacteriology, 141:868-875.
Matsumoto A, 1982. Surface projections of Chlamydia psittaci elementary bodies as revealed by freeze-deep-etching. Journal of Bacteriology, 151:1040-1042.
Matsumoto A, 1988. Structural characteristics of chlamydial bodies. In: Baron AL, ed. Microbiology of Chlamydia. Boca Raton, Fl., USA: CRC Press, 21-45.
Rockey DD; Matsumoto A, 2000. The chlamydial developmental cycle. In: Brun YV, Shimkets LJ, eds. Prokaryotic Development. Washington DC, USA: ASM Press, 403-425.
Soloff B; Rank RG; Barron AL, 1982. Ultrastructural studies of chlamydial infection in guinea-pig urogenital tract. Journal of Comparative Pathology, 92:547.
Storz J, 1971. Chlamydia and Chlamydia-Induced Diseases. Springfield, IL, USA: Charles C. Thomas, Publisher.