Intracellular pathogens go extreme: genome evolution in the Rickettsiales

Darby, Alistair C.; Cho, Nam Huyk; Fuxelius, Hans Henrik; Westberg, Joakim; Andersson, Siv G. E.

doi:10.1016/j.tig.2007.08.002

Cited by 188 publications

(175 citation statements)

References 39 publications

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“…The observation that 50% of the amoeba-associated bacteria included in our analysis are also well-known pathogens of humans suggests that the development of these mechanisms not only was fundamental for the survival in amoebae but also primed the evolution of bacteria able to infect higher eukaryotes. Our data thus lend novel support for the suggested role of amoebae as a major training ground for the evolution of bacterial pathogens of humans (2,24,42,78,89).…”

Section: Resultssupporting

confidence: 58%

“…These protozoa can thus serve as reservoirs and vectors for the transmission of pathogenic bacteria to humans, as demonstrated for L. pneumophila and Mycobacterium avium (2, 115). It is also increasingly being recognized that protozoa are important for the adaptation of (pathogenic) bacteria to higher eukaryotic cells as a niche for growth (2,24,42,78,89).In addition to the many recognized transient associations between amoeba and pathogens, stable and obligate relationships between bacteria and amoebae also were described for members of the Alphaproteobacteria (11, 34, 48), the Betaproteobacteria (49), the Bacteroidetes (50), and the Chlamydiae (4, 12, 35, 52). These obligate amoeba symbionts show a worldwide distribution, since phylogenetically highly similar strains were found in amoeba isolates from geographically distant sources (51, 107).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…Numerous genome sequences from the Alpha-and Gammaproteobacteria and the Chlamydiae are available and have contributed significantly to our understanding of genome evolution, the biology of intracellular bacteria, and the interactions with their host cells (24,26,46,79,82). In this study, we determined and analyzed the complete genome sequence of "Candidatus Amoebophilus asiaticus" strain 5a2 in order to gain novel insights into its biology.…”

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confidence: 99%

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The Genome of the Amoeba Symbiont “CandidatusAmoebophilus asiaticus” Reveals Common Mechanisms for Host Cell Interaction among Amoeba-Associated Bacteria

et al. 2010

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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.Free-living amoebae, such as Acanthamoeba spp., are ubiquitous protozoa which can be found in such diverse habitats as soil, marine water, and freshwater and in many engineered environments (62, 100). They are important predators of prokaryotic and eukaryotic microorganisms, thereby having great influence on microbial community composition, soil mineralization, plant growth, and nutrient cycles (14, 100). Interestingly, many well-known pathogens of humans are able to infect, survive, and multiply within amoebae (39, 51). These protozoa can thus serve as reservoirs and vectors for the transmission of pathogenic bacteria to humans, as demonstrated for L. pneumophila and Mycobacterium avium (2, 115). It is also increasingly being recognized that protozoa are important for the adaptation of (pathogenic) bacteria to higher eukaryotic cells as a niche for growth (2,24,42,78,89).In addition to the many recognized transient associations between amoeba and pathogens, stable and obligate relationships between bacteria and amoebae also were described for members of the Alphaproteobacteria (11, 34, 48), the Betaproteobacteria (49), the Bacteroidetes (50), and the Chlamydiae (4, 12, 35, 52...

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Section: Resultssupporting

confidence: 58%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

The Genome of the Amoeba Symbiont “CandidatusAmoebophilus asiaticus” Reveals Common Mechanisms for Host Cell Interaction among Amoeba-Associated Bacteria

et al. 2010

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“…bacteria can be vertically inherited from mother to offspring, which is not the case for Anaplasma and Ehrlichia (Fig. 2) (2,5). Whether one of these differences in life style requires a c-di-GMP PDE remains to be shown.…”

Section: Lack Of a C-di-gmp Pde Homologue In A Phagocytophilummentioning

confidence: 99%