Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/1998
Publication Date: N/A
Interpretive Summary: Currently, the bacteria that are classified as Chlamydia are grouped into four species. Two of these species predominantly infect people. The other two species infect a variety of animals. These species groupings are based on very limited information. Analysis of the sequences of Chlamydia genes has allowed us to clearly distinguish two major types of Chlamydia that contain a total of nine groups. In addition to these human and animal strains, chlamydiae have been found growing in amoebae. These and other new strains of chlamydiae form at least three completely new groupings. In this report, a new taxonomy for these groups is presented. Chlamydial strains belonging to the families, genera, and species in the new taxonomic groups are readily distinguished by short segments of DNA sequence. This taxonomy provides a reliable system for identifying new strains.
Technical Abstract: Recent studies indicate that the order Chlamydiales contains at least four distinct taxa, including Chlamydiaceae, Simkania, Parachlamydia, and Waddlia, and that the family Chlamydiaceae has two distinct lineages which branch into nine taxa. These taxa are closely related according to 16S rRNA sequencing and are supported by a broad base of genetic and phenotypic canalyses. In this report, we propose a reclassification of the order Chlamydiales and its taxa. This proposal retains currently known strains with >90% 16S or 23S rRNA identity in the family Chlamydiaceae and separates other chlamydia-like organisms that have 80% - 90% 16S or 23S rRNA relatedness to Chlamydiaceae into new families. Two new families and species are created: Simkaniaceae fam. nov., Simkania negevensis gen. nov., sp. nov., and Parachlamydiaceae fam. nov., Parachlamydia acanthamoebae gen. nov., sp. nov. A second genus is created in the family Chlamydiaceae, and current Chlamydia strains and species are divided between these two genera. Within each genus, the 16S rRNA sequences of the strains are >95% identical. The four current species are expanded into a total of nine species. These families, genera, and species are readily distinguished by analysis of signature sequences in the 16S and 23S ribosomal genes. This new taxonomy provides a systematic rationale for identifying new strains.