The untold diversity of chlamydiae was first revealed in 1990s when a chlamydia-like bacteria was recognized with free-living amoeba as endosymbiont. Snce then, tey have been considered as novel members of the order Chlamydiales. Tis discovery led to the reorganization of the chlamydial taxonomy as three new families were added (Collingro et al. Iitially, te phylum Chlamydiae is composed of a single class which is Chlamydiae which is composed of the order Chlamydiales. Wth the addition of the three new families, tis order is now composed of four the Chlamydiaceae, wich contains all of the traditional chlamydiae species and the novel chlamydia species (Griffiths et al.
Tese novel chlamydiae were proposed to be classified as Parachlamydiaceae, Smkaniaceae and Waddliaceae (Collingro et al. Snce chlamydia-like species are found mostly in non-culturable sources, i is difficult to obtain information regarding it sequences. Te only way to do so however, i through PCR amplification using primers based on 16S rRNA sequences and the clustering of any amplified sequence with the known chlamydiae species in the rRNA trees (Griffiths, 2005). T symbionts to their evolutionary lineages, te application of the full cycle rRNA approach which included 16S rRNA sequencing and fluorescence in situ hybridization with 16S rRNA-targeted oligonucleotide probes was used (Horn et al.
Fritsche et al. 2000) however used neighbor-joining, prsimony and distance matrix methods in analyzing the 16S rRNA gene sequences of acanthamoeba isolates with their aim to uncover the diversity of Chlamydiales. Tey further used fluorescently labeled oligonucleotide probes to target 16S rRNA to differentiate the two groups of intra-amoebal endosymbionts. Sudies have shown that at point the evolutionary history, te Chlamydiales diverged which resulted to the present families.
I spite of this divergence, al families under order Chlamydiales share common characteristics. Te 16S rRNA of all families is about 80 to 90% related to each other. Ecept for endosymbionts of Parachlamydiaceae, al are obligate intracellular parasites. Oly the elementary bodies of Parachlamydia acanthamoeba retain the Gram stain which may be explained by the thick cell envelopes. Al the rest are Gram-negative. Pelomorphism is another distinct. ..
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