Chlamydia trachomatis: Difference between revisions
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==Cell structure and metabolism== | ==Cell structure and metabolism== | ||
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces. | Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces. | ||
The life cycle of C. trachomatis consists of two stages: elementary body and reticulate body. The elementary body is the dispersal form and is analogous to a spore. It is approximately 0.3 um in diameter and induces its own endocytosis upon exposure to target cells. It is this form that prevents phagolysosomal fusion and hence allows for intracellular survival. Once inside the endosome, the glycogen produced causes the elementary body to "germinate" into the vegetative form, the reticulate body. This form divides by binary fission at approximately 2-3 hours per generation. It has an incubation period of 7-21 days in the host. It contains no cell wall and (when stained with iodine) is detected as an inclusion in the cell. After division, the reticulate body transforms back to the elementary form and is released by the cell by exocytosis. One phagolysosome usually produces 100-1000 elementary bodies. | |||
==Ecology== | ==Ecology== | ||
Revision as of 07:42, 1 May 2007
Classification
Higher order taxa
Archaea; Euryarchaeota; Thermoplasmata; Thermoplasmatales; Thermoplasmataceae; Thermoplasma
Genus
Chlamydiaceae
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NCBI: Taxonomy |
Description and significance
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
round or occasionally pear shaped, electron-dense structures approximately 0.3 microns in diameter. The Elementary bodies is the only infectious stage of the chlamydial developmental cycle. It functions as a tough "spore-like" body whose purpose is to permit chlamydial survival in the non-supportive (to chlamydiae) environment outside the host cell. The EB is thought to be metabolically inert until it attaches to, and is endocytosed by, a susceptible host cell. It contains only small amounts of the usual bacterial cell wall strengthening substance, peptidoglycan. Instead it derives its strength, among other things, from cross links [-S-S- bridges] formed between the sulphur atoms of its sulphur amino acid rich proteins in the outer envelope.
The reticulate body is the stage of the chlamydial developmental cycle responsible for intracellular replication. Typically, reticulate bodies have a diameter of 1 micron or more and they are non infectious. Reticulate bodies are metabolically active, so their cytoplasm is rich in ribosomes, which are required for protein synthesis. Their nucleic acid appears diffuse and fibrillar. They are bounded by two sets of tri-laminar membranes, an inner cytoplasmic membrane and an external outer envelope, whose surface is covered with projections and rosettes similar to those seen on elementary bodies, but at higher density.
The chlamydial outer membrane complex is composed primarily of three proteins; the major outer membrane protein (MOMP) and two cysteine-rich proteins, the outer membrane complex B protein (OmcB) and the outer membrane complex A protein (OmcA). Chlamydial major outer membrane protein, which by reason of its importance is the most extensively studied, was discovered in 1981 by three independent laboratories
SDS - PAGE electrophoresis
Genome structure
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Chlamydia trachomatis has a genome size that is 1,042,519 base pairs long and has approximately 894 protein coding sequences. C. trachomatis strains have an extrachromosomal plasmid. ll plasmids from human C. trachomatis isolates are extremely similar, with less than 1% nucleotide sequence variation All are about 7,500 nucleotides in size, with eight open reading frames computer-predicted to code for proteins of more than 100 amino acids, with short non-coding sequences between some of them only
In their nucleotide sequence, chlamydial plasmids are more closely related than is the corresponding chromosomal DNA
The chlamydial plasmid has great practical importance. It is a favoured target for DNA-based diagnosis of C. trachomatis infection for two reasons. Firstly, there are approximately 7-10 copies of the plasmid present per chlamydial particle. Its sequence is highly conserved among different isolates of C. trachomatis. There are authenticated examples of C. trachomatis strains lacking the plasmid and it does have effects. Plaque purified C. trachomatis free of the plasmid has unusual inclusion morphology, is glycogen free, and shows no alteration in antibiotic sensitivity . However, the fact that such strains exist shows that the plasmid is not essential for C. trachomatis survival.
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
The life cycle of C. trachomatis consists of two stages: elementary body and reticulate body. The elementary body is the dispersal form and is analogous to a spore. It is approximately 0.3 um in diameter and induces its own endocytosis upon exposure to target cells. It is this form that prevents phagolysosomal fusion and hence allows for intracellular survival. Once inside the endosome, the glycogen produced causes the elementary body to "germinate" into the vegetative form, the reticulate body. This form divides by binary fission at approximately 2-3 hours per generation. It has an incubation period of 7-21 days in the host. It contains no cell wall and (when stained with iodine) is detected as an inclusion in the cell. After division, the reticulate body transforms back to the elementary form and is released by the cell by exocytosis. One phagolysosome usually produces 100-1000 elementary bodies.
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
example:
Edited by student of Rachel Larsen and Kit Pogliano
