Extreme diversity of the Order Chlamydiales

[Drs Ossewaarde and Meijer in Rotterdam have developed new PCR probes specific for the order Chlamydiales. These new probes are beginning to expand our horizons of  the diversity and enormous host range of this group of organisms.  Here Meijer and Ossewaarde present evidence that the families Parachlamydiaceae, Waddliaceae and Simkaniaceae are insufficient to support the classification of over 100 new Chlamydiales-like 16S rDNA sequences.

Chlamydiae.com is pleased to reproduce their presentation to the International Chlamydia Conference at Antalya, Turkey in June 2002].

Fig 1. Title. These figures © Meijer & Ossewaarde  2002.	Fig 2. Initial studies, 1999 and 4 new Chlamydiales like sequences discovered based on DNA encoding ribosomal RNA.	Fig 3.  New PCR primers designed based on 16S rDNA.	Fig 4. A surprising number of new Chlamydiales-related gene sequences revealed, Helsinki 2000.
Fig 5. Antalya 2002: More than 100 Chlamydiales-like sequences.	Fig 6. The PCR and sequencing strategy.	Fig 7. Sequence analysis.	Fig 8. A wide range of hosts targeted, from the aqueous environment, through fish and reptiles to humans.
Fig 9. General impression of the phylogenetic tree for all the Chlamydiales-like sequences. Note how many of the sequences are related to, but do not directly belong in, existing genera and families.	Fig 10. Specimens were recovered from a variety of human sources, including aqueous humour.	Fig 11. Specimens recovered from diverse animal sources.	Fig 12. Evidence for Chlamydophila species in the liver of a Nile crocodile.
Fig 13. Evidence for Chlamydophila species in the ovary of a snake.	Fig 14. Diagram showing how the rDNA sequences from the crocodile and snake are closely related to other Chlamydophila species found in animals.	Fig 15. The diverse fish species from which Chlamydiales-like sequences were identified.	Fig 16. Lesions in fish reactive with Chlamydiales probe.
Fig 17. Predicted secondary structure of 16S rDNA from an unknown Chlamydiales organism in CRG 18 and from Neochlamydia hartmannellae, a Chlamydiales organism found in amoebae.	Fig 18. Relationship of CRG 18 and other unknown sequences to the Neochlamydiaceae.	Fig 19. Results from environmental specimens and controls.	Fig 20. Phyllogenetic tree around the Waddliaceae.
Fig 21. The Chlamydiales super family.	Fig 22. Conclusions.

NEXT: Chlamydiales evolution - foreword

See also: "Chlamydia-like" organisms

See also: Environmental chlamydia

See also: Evolutionary divergence

See also: In situ hybridization for Chlamydiales

[August 2003]

References

Corsaro, D., Valassina, M. & Venditti, D. (2003). Increasing diversity within Chlamydiae. Critical Reviews in Microbiology 29, 37 - 78. [Review].

Meijer, A. & Ossewarde, J. M. (2002). Description of a wider diversity within the order Chlamydiales than currently classified. In: Stephens R. S. et al., (eds). Human Chlamydial Infections. Proceedings of the Tenth International Conference on Human Chlamydial infections. Publisher: International Chlamydia Symposium, San Francisco USA, ISBN 0-9664383-1-0