Phylogenetic diversity among geographically dispersed Chlamydiales endosymbionts recovered from clinical and environmental isolates of Acanthamoeba spp.

The recently proposed reorganization of the order Chlamydiales and description of new taxa are broadening our perception of this once narrowly defined taxon. We have recovered four strains of gram-negative cocci endosymbiotic in Acanthamoeba spp., representing 5% of the Acanthamoeba sp. isolates examined, which displayed developmental life cycles typical of members of the Chlamydiales. One of these endosymbiont strains was found stably infecting an amoebic isolate recovered from a case of amoebic keratitis in North America, with three others found in acanthamoebae recovered from environmental sources in North America (two isolates) and Europe (one isolate). Analyses of nearly full-length 16S rRNA gene sequences of these isolates by neighbor joining, parsimony, and distance matrix methods revealed their clustering with other members of the Chlamydiales but in a lineage separate from those of the genera Chlamydia, Chlamydophila, Simkania, and Waddlia (sequence similarities,