**4. Taxonomy of Clamydiae**

The taxonomy used for classifying living organisms was discovered by Carl von Linne (Linnaeus) in 1735. This system, which is used by all biologists, still remains the basis for classifying living organisms today. In this classification, Chlamydiae, which have a prokaryotic cell structure, were initially considered as bacteria-like organisms. In the taxonomic classification, Chlamydiae belong to the domain bacteria and the order Chlamydiales [2].


#### **Table 1.** *Chlamydial taxonomy [2, 13].*

Until the molecular studies conducted by Everet, Bush, and Anderson, Chlamydiae, considered a single family, was divided into four different families and included in the classification (**Table 1**). These families are Chlamydiaceae, Simkaniaceae, Parachlamydiaceae, and Waddliaceae within the Chlamydiales order. Within the Chlamydiaceae family, based on the sequence analysis of the 16S and 23S rRNA genes, two genera (*Chlamydia* and *Chlamydophila*) and nine species were reclassified [15].

The truth is that the changes in the taxonomic classification of *Chlamydia* proposed by Everett and Everett et al. (1999) are not accepted by many. The fact that this new classification is not used in studies conducted in the field of human medicine is an indication of this. The use of more molecular markers in classification can eliminate these uncertainties. However, there is no confusion in the classification of *Chlamydia* agents in animals [13].
