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The Genome of the Amoeba Symbiont “Candidatus Amoebophilus asiaticus” Reveals Common Mechanisms for Host Cell Interaction among Amoeba-Associated Bacteria
Journal of Bacteriology (2010)
  • Stephan Schmitz-Esser, University of Vienna
  • Patrick Tischler, Technische Universität München
  • Roland Arnold, Technische Universität München
  • Jacqueline Montanaro, University of Vienna
  • Michael Wagner, University of Vienna
  • Thomas Rattei, Technische Universität München
  • Matthias Horn, University of Vienna
Protozoa play host for many intracellular bacteria and are important for the adaptation of pathogenic
bacteria to eukaryotic cells. We analyzed the genome sequence of “Candidatus Amoebophilus asiaticus,” an
obligate intracellular amoeba symbiont belonging to the Bacteroidetes. The genome has a size of 1.89 Mbp,
encodes 1,557 proteins, and shows massive proliferation of IS elements (24% of all genes), although the genome seems to be evolutionarily relatively stable. The genome does not encode pathways for de novo biosynthesis of cofactors, nucleotides, and almost all amino acids. “Ca. Amoebophilus asiaticus” encodes a variety of proteins with predicted importance for host cell interaction; in particular, an arsenal of proteins with eukaryotic domains, including ankyrin-, TPR/SEL1-, and leucine-rich repeats, which is hitherto unmatched among
prokaryotes, is remarkable. Unexpectedly, 26 proteins that can interfere with the host ubiquitin system were
identified in the genome. These proteins include F- and U-box domain proteins and two ubiquitin-specific
proteases of the CA clan C19 family, representing the first prokaryotic members of this protein family.
Consequently, interference with the host ubiquitin system is an important host cell interaction mechanism of
“Ca. Amoebophilus asiaticus”. More generally, we show that the eukaryotic domains identified in “Ca.
Amoebophilus asiaticus” are also significantly enriched in the genomes of other amoeba-associated bacteria
(including chlamydiae, Legionella pneumophila, Rickettsia bellii, Francisella tularensis, and Mycobacterium
avium). This indicates that phylogenetically and ecologically diverse bacteria which thrive inside amoebae
exploit common mechanisms for interaction with their hosts, and it provides further evidence for the role of
amoebae as training grounds for bacterial pathogens of humans.
Publication Date
February, 2010
Publisher Statement
© 2010, American Society for Microbiology.
Citation Information
Stephan Schmitz-Esser, Patrick Tischler, Roland Arnold, Jacqueline Montanaro, et al.. "The Genome of the Amoeba Symbiont “Candidatus Amoebophilus asiaticus” Reveals Common Mechanisms for Host Cell Interaction among Amoeba-Associated Bacteria" Journal of Bacteriology Vol. 192 Iss. 4 (2010) p. 1045 - 1057
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