Chlamydia trachomatis
Scientific classification
Domain: Bacteria
Phylum: Chlamydiae
Class: Chlamydiae
Order: Chlamydiales

Candidatus Piscichlamydia salmonis♠ Draghi et al. 2004
Candidatus Criblamydiaceae♠
Candidatus Rhabdochlamydiaceae

Chlamydiae is a bacterial phylum and class whose members are obligate intracellular pathogens.[1] Many Chlamydiae coexist in an asymptomatic state within specific hosts, and it is widely believed that these hosts provide a natural reservoir for these species.[2]

All known Chlamydiae only grow by infecting eukaryotic host cells. They are as small or smaller than many viruses. Chlamydiae replicate inside the host cells and are termed intracellular. Most intracellular Chlamydiae are located in an inclusion body or vacuole. Outside of cells they survive only as an extracellular infectious form. Chlamydiae can grow only where their host cells grow. Therefore, Chlamydiae cannot be propagated in bacterial culture media in the clinical laboratory. Chlamydiae are most successfully isolated while still inside their host cell.

Cavalier-Smith has postulated that the Chlamydiae fall into the clade Planctobacteria in the larger clade Gracilicutes.



Chlamydia-like disease affecting the eyes of people was first described in ancient Chinese and Egyptian manuscripts. A modern description of Chlamydia-like organisms was provided by Halberstaedter and von Prowazek in 1907. Chlamydial isolates cultured in the yolk sacs of embryonating eggs were obtained from a human pneumonitis outbreak in the late 1920s and early 1930s, and by the mid-20th Century isolates had been obtained from dozens of vertebrate species. The term Chlamydia (a cloak) appeared in the literature in 1945, although other names continued to be used, including Bedsonia, Miyagawanella, ornithosis-, TRIC-, and PLT-agents.


In 1966, Chlamydiae were recognized as bacteria and the genus Chlamydia was validated.[3] The Order Chlamydiales was created by Storz and Page in 1971.[4] Between 1989 and 1999, new families, genera, and species were recognized. The phylum Chlamydiae was established in Bergey's Manual of Systematic Bacteriology.[5]

By 2006, genetic data for over 350 chlamydial lineages had been reported,[6] four chlamydial families had been recognized (Chlamydiaceae, Parachlamydiaceae, Simkaniaceae, and Waddliaceae),[7][8] and another family had been proposed (Rhabdochlamydiaceae).


Chlamydiae is a unique bacterial evolutionary group that separated from other bacteria approximately a billion years ago.[9][10] Reports have varied as to whether Chlamydiae is related to Planctomycetales or Spirochaetes.[11][12] 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.[10] Comparison of ribosomal RNA genes has provided a phylogeny of known strains within Chlamydiae.[6] The unique status of Chlamydiae has enabled the use of DNA analysis for chlamydial diagnostics.[13]

There are three described species of chlamydiae that commonly infect humans:



?Candidatus Piscichlamydia salmonis♠

?Candidatus Criblamydiaceae♠


Candidatus Rhabdochlamydiaceae




♠ Strain found at the National Center for Biotechnology Information (NCBI) but has no standing with the Bacteriological Code (1990 and subsequent Revision) as detailed by List of Prokaryotic names with Standing in Nomenclature (LPSN) as a result of the following reasons:
• No pure culture isolated or available for Prokayotes.
• Not validly published because the effective publication only documents deposit of the type strain in a single recognized culture collection.
• Not approved and published by the International Journal of Systematic Biology or the International Journal of Systematic and Evolutionary Microbiology (IJSB/IJSEM).


  1. ^ Wyrick P (2000). "Intracellular survival by Chlamydia". Cell Microbiol 2 (4): 275–82. doi:10.1046/j.1462-5822.2000.00059.x. PMID 11207584. 
  2. ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0838585299. 
  3. ^ Moulder J (1966). "The relation of the psittacosis group (Chlamydiae) to bacteria and viruses". Annu Rev Microbiol 20: 107–30. doi:10.1146/annurev.mi.20.100166.000543. PMID 5330228. 
  4. ^ Storz J, Page LA (1971). "Taxonomy of the Chlamydiae: reasons for classifying organisms of the genus Chlamydia, family Chlamydiaceae, in a separate order, Chlamydiales ord. nov". International Journal of Systematic Bacteriology 21: 332–334. doi:10.1099/00207713-21-4-332. 
  5. ^ Garrity GM, Boone DR (editors) (2001). Bergey's Manual of Systematic Bacteriology Volume 1: The Archaea and the Deeply Branching and Phototrophic Bacteria (2nd ed.). Springer. ISBN 0387987711. 
  6. ^ a b Everett K, Thao M, Horn M, Dyszynski G, Baumann P (2005). "Novel chlamydiae in whiteflies and scale insects: endosymbionts 'Candidatus Fritschea bemisiae' strain Falk and 'Candidatus Fritschea eriococci' strain Elm". Int J Syst Evol Microbiol 55 (Pt 4): 1581–7. doi:10.1099/ijs.0.63454-0. PMID 16014485. 
  7. ^ Everett K, Bush R, Andersen A (1999). "Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms". Int J Syst Bacteriol 49 Pt 2: 415–40. doi:10.1099/00207713-49-2-415. PMID 10319462. 
  8. ^ Rurangirwa F, Dilbeck P, Crawford T, McGuire T, McElwain T (1999). "Analysis of the 16S rRNA gene of micro-organism WSU 86-1044 from an aborted bovine foetus reveals that it is a member of the order Chlamydiales: proposal of Waddliaceae fam. nov., Waddlia chondrophila gen. nov., sp. nov". Int J Syst Bacteriol 49 Pt 2: 577–81. PMID 10319478. 
  9. ^ Greub G, Raoult D (2003). "History of the ADP/ATP-translocase-encoding gene, a parasitism gene transferred from a Chlamydiales ancestor to plants 1 billion years ago". Appl Environ Microbiol 69 (9): 5530–5. doi:10.1128/AEM.69.9.5530-5535.2003. PMC 194985. PMID 12957942. 
  10. ^ a b Horn M, Collingro A, Schmitz-Esser S, Beier C, Purkhold U, Fartmann B, Brandt P, Nyakatura G, Droege M, Frishman D, Rattei T, Mewes H, Wagner M (2004). "Illuminating the evolutionary history of chlamydiae". Science 304 (5671): 728–30. doi:10.1126/science.1096330. PMID 15073324. 
  11. ^ Ward N, Rainey F, Hedlund B, Staley J, Ludwig W, Stackebrandt E (2000). "Comparative phylogenetic analyses of members of the order Planctomycetales and the division Verrucomicrobia: 23S rRNA gene sequence analysis supports the 16S rRNA gene sequence-derived phylogeny". Int J Syst Evol Microbiol 50 Pt 6: 1965–72. PMID 11155969. 
  12. ^ Teeling H, Lombardot T, Bauer M, Ludwig W, Glöckner F (2004). "Evaluation of the phylogenetic position of the planctomycete 'Rhodopirellula baltica' SH 1 by means of concatenated ribosomal protein sequences, DNA-directed RNA polymerase subunit sequences and whole genome trees". Int J Syst Evol Microbiol 54 (Pt 3): 791–801. doi:10.1099/ijs.0.02913-0. PMID 15143026. 
  13. ^ Corsaro D, Greub G (2006). "Pathogenic potential of novel Chlamydiae and diagnostic approaches to infections due to these obligate intracellular bacteria". Clin Microbiol Rev 19 (2): 283–97. doi:10.1128/CMR.19.2.283-297.2006. PMC 1471994. PMID 16614250. 
  14. ^ "Bergey's Taxonomic Outlines: Volume 4 - Draft Taxonomic Outline of the Bacteroidetes, Planctomycetes, Chlamydiae, Spirochaetes, Fibrobacteres, Fusobacteria, Acidobacteria, Verrucomicrobia, Dictyoglomi, and Gemmatimonadetes", Bergey's Manual Trust: 15, 2008, 

External links

  •, a comprehensive information source from Dr. Michael Ward (Professor of Medical Microbiology in the University of Southampton)

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