|Cell Wall: Gram Negative||Life Cycle: Obligate Intracellular Parasite|
- Chlamydia refers to a genus of related bacterial species with similar cell walls, who are obligate intracellular parasites, and possess a similar life cycle. Architecturally, the chlamydial cell wall is analogous to those of gram negative bacteria, with an inner and outer lipid membrane (See: Bacterial Cell Wall). As obligate intracellular parasites, chlamydial species can only multiply within cells because they cannot produce their own ATP and must derive this energy source from the host cells which they infect.
- The life cycle of chlamydia is complex since it cannot replicate outside of living cells but obviously must exit a cell in order to be transmitted. Therefore, the bacteria can transition between two basic forms, one of which is specialized for intracellular proliferation, and the other specialized for extracellular transmission.
- Elementary Body (EB)
- This small and dense form is the infections particle that is transmitted from cell to cell and from individual to individual. The EB membrane possesses a high density of cross-linked membrane proteins which render the particle resistant to environmental insults. EBs have a predilection for adhering to columnar epithelia and are probably internalized by a number of mechanisms, ultimately ending up in endosomes. Once inside endosomes, the EBs reorganize into the RB form within a matter of hours and begin to replicate.
- Reticulate Body (RB)
- This is the replicative form of the bacteria that exists inside a host cell's endosomes. Rapid replication of the bacteria inside the endosome can be observed microscopically as a membrane-bound cellular vacuole full of bacteria and is termed an "Inclusion Body". Over time, the RBs transition back to the environmentally-resistant EB form and the cell is lysed, releasing infectious EB particles.
- All chlamydial species are treated with either tetracycline or erythromycin.