Genomics
Chlamydiae is a unique bacterial evolutionary group that separated from other bacteria approximately a billion years ago. The species from this group can be distinguished from all other bacteria by the presence of conserved indels in a number of proteins such as RNA polymerase alpha subunit, Gyrase B, Elongation factor-Tu and Elongation factor-P, and by large numbers of signature proteins that are uniquely present in different chlamydiae species. Reports have varied as to whether Chlamydiae is related to Planctomycetales or Spirochaetes. Genome sequencing, however, indicates that 11% of the genes in Candidatus Protochlamydia amoebophila UWE25 and 4% in Chlamydiaceae are most similar to chloroplast, plant, and cyanobacterial genes. However, phylogeny and shared presence of conserved indels in proteins such as RNA polymerase Beta subunit and lysyl-tRNA synthetase indicate that Verrucomicrobia are the closest free-living relatives of these parasitic organisms. Comparison of ribosomal RNA genes has provided a phylogeny of known strains within Chlamydiae. The unique status of Chlamydiae has enabled the use of DNA analysis for chlamydial diagnostics.
There are three described species of chlamydiae that commonly infect humans:
- Chlamydia trachomatis, which causes the eye-disease trachoma and the sexually transmitted infection chlamydia;
- Chlamydia pneumoniae, which causes a form of pneumonia;
- Chlamydia psittaci, which causes psittacosis.
Read more about this topic: Chlamydiae