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Applied and Environmental Microbiology, June 2000, p. 2613-2619, Vol. 66, No. 6
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Phylogenetic Diversity among Geographically Dispersed Chlamydiales Endosymbionts Recovered from Clinical and Environmental Isolates of Acanthamoeba spp.

Thomas R. Fritsche,1,* Matthias Horn,2 Michael Wagner,2 Russell P. Herwig,3 Karl-Heinz Schleifer,2 and Romesh K. Gautom4

Department of Laboratory Medicine1 and School of Fisheries,3 University of Washington, Seattle, Washington 98195; Lehrstuhl für Mikrobiologie, Technische Universität München, 85350 Freising, Germany2; and Washington State Public Health Laboratory, Seattle, Washington 981554

Received 22 September 1999/Accepted 8 March 2000

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, <88%) and including the recently described species Parachlamydia acanthamoebae (sequence similarities, 91.2 to 93.1%). With sequence similarities to each other of 91.4 to 99.4%, these four isolates of intra-amoebal endosymbionts may represent three distinct species and, perhaps, new genera within the recently proposed family Parachlamydiaceae. Fluorescently labeled oligonucleotide probes targeted to 16S rRNA signature regions were able to readily differentiate two groups of intra-amoebal endosymbionts which corresponded to two phylogenetic lineages. These results reveal significant phylogenetic diversity occurring among the Chlamydiales in nontraditional host species and supports the existence of a large environmental reservoir of related species. Considering that all described species of Chlamydiales are known to be pathogenic, further investigation of intra-amoebal parachlamydiae as disease-producing agents is warranted.

* Corresponding author. Mailing address: Department of Laboratory Medicine, University of Washington, 1959 N.E. Pacific St., Seattle, WA 98195-7110. Phone: (206) 598-6131. Fax: (206) 598-6189. E-mail: fritsche{at}u.washington.edu.

Applied and Environmental Microbiology, June 2000, p. 2613-2619, Vol. 66, No. 6
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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