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Bacterial Endosymbionts of Free-living Amoebae1

Authors

  • MATTHIAS HORN,

    Corresponding author
    1. Division of Microbial Ecology, Institute of Ecology and Conservation Biology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
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  • MICHAEL WAGNER

    1. Division of Microbial Ecology, Institute of Ecology and Conservation Biology, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
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  • 1

    Symposium presentation “Bacterial Endosymbionts or Pathogens of Free-Living Amebae” presented June 5th, 2004, during the 56th Annual Meeting of the Society of Protozoologists, June 2-6, Bryant College, Smithfield, Rhode Island, USA.

Corresponding Author: M. Horn—Telephone number: +43 1 4277 54393; Fax number: +43 1 4277 54389; E-mail: horn@microbial-ecology.net

ABSTRACT

The occurrence of bacterial endosymbionts in free-living amoebae has been known for decades, but their obligate intracellular lifestyle hampered their identification. Application of the full cycle rRNA approach, including 16S rRNA gene sequencing and fluorescence in-situ hybridization with 16S rRNA-targeted oligonucleotide probes, assigned the symbionts of Acanthamoeba spp. and Hartmannella sp. to five different evolutionary lineages within the Proteobacteria, the Bacteroidetes, and the Chlamydiae, respectively. Some of these bacterial symbionts are most closely related to bacterial pathogens of humans, and it has been suggested that they should be considered potential emerging pathogens. Complete genome sequence analysis of a chlamydia-related symbiont of Acanthamoeba sp. showed that this endosymbiont uses similar mechanisms for interaction with its eukaryotic host cell as do the well-known bacterial pathogens of humans. Furthermore, phylogenetic analysis suggested that these mechanisms have been evolved by the ancestor of these amoeba symbionts in interplay with ancient unicellular eukaryotes.

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