Chlamydia infections are the most common bacterial sexually transmitted diseases in humans and are the leading cause of infectious blindness worldwide.

[7] In 2009 the validity of Chlamydophila was challenged by newer DNA analysis techniques, leading to a proposal to "reunite the Chlamydiaceae into a single genus, Chlamydia".

The elementary body contains an RNA polymerase responsible for the transcription of the DNA genome after entry into the host cell cytoplasm and the initiation of the growth cycle.

The elementary body is the nonreplicating infectious particle that is released when infected cells rupture.

The reticular body is basically the structure in which the chlamydial genome is transcribed into RNA, proteins are synthesized, and the DNA is replicated.

After division, the reticulate body transforms back to the elementary form and is released by the cell by exocytosis.

[14] A histone like protein HctA and HctB play role in controlling the differentiation between the two cell types.

The expression of HctA is tightly regulated and repressed by small non-coding RNA, IhtA until the late RB to EB re-differentiation.

[17] Symptomatic infections often include a burning sensation when urinating and abdominal or genital pain and discomfort.

[18] All people who have engaged in sexual activity with potentially infected individuals may be offered one of several tests to diagnose the condition.

[19] Recent phylogenetic studies have revealed that Chlamydia likely shares a common ancestor with cyanobacteria, the group containing the endosymbiont ancestor to the chloroplasts of modern plants, hence, Chlamydia retains unusual plant-like traits, both genetically and physiologically.

In particular, the enzyme L,L-diaminopimelate aminotransferase, which is related to lysine production in plants, is also linked with the construction of chlamydial peptidoglycan, which is required for division.

[20] The genetic encoding for the enzymes is remarkably similar in plants, cyanobacteria, and Chlamydia, demonstrating a close common ancestry.

Fukushi & Hirai 1992 Chlamydia pneumoniae Grayston et al. 1989 C. muridarum Everett, Bush & Andersen 1999 C. suis Everett, Bush & Andersen 1999 C. trachomatis (Busacca 1935) Rake 1957 Chlamydophila C. trachomatis C. muridarum C. suis Chlamydophila