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What makes pathogens pathogenic.

Ehrlich GD, Hiller NL, Hu FZ - Genome Biol. (2008)

Bottom Line: Metazoans contain multiple complex microbial ecosystems in which the balance between host and microbe can be tipped from commensalism to pathogenicity.This transition is likely to depend both on the prevailing environmental conditions and on specific gene-gene interactions placed within the context of the entire ecosystem.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Genomic Sciences, Allegheny General Hospital, Allegheny Singer Research Institute, Pittsburgh, PA 15212, USA. gehrlich@wpahs.org

ABSTRACT
Metazoans contain multiple complex microbial ecosystems in which the balance between host and microbe can be tipped from commensalism to pathogenicity. This transition is likely to depend both on the prevailing environmental conditions and on specific gene-gene interactions placed within the context of the entire ecosystem.

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Related in: MedlinePlus

The distributed genome hypothesis. (a) Schematic showing the distributed (non-core) genes of a species supragenome in a population pool with individual strains below each containing the same set of core genes (green helix). (b) Schematic showing each of the strains of a species with the core genome and a unique distribution of non-core genes.
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Figure 1: The distributed genome hypothesis. (a) Schematic showing the distributed (non-core) genes of a species supragenome in a population pool with individual strains below each containing the same set of core genes (green helix). (b) Schematic showing each of the strains of a species with the core genome and a unique distribution of non-core genes.

Mentions: The distributed genome hypothesis [35,36] states that bacterial pathogens arise and acquire virulence traits primarily via horizontal gene transfer (Figure 1). More recently, it has become clear that many bacteria are multicellular organisms during part of their life cycle [37], and this has led to the recognition that bacteria possess a number of virulence traits that are expressed only at the population level and are not operational at the single-cell level [38]. These hypotheses are based on the observation that nearly all classes of pathogenic bacteria maintain highly energy-demanding mechanisms for accessing foreign DNA [39], in spite of the fact that most of these species maintain small genomes. The importance of this observation is that in a background of processes that favor gene deletion [40], the maintenance of multiple horizontal gene transfer mechanisms indicates that these traits are highly selected for. The distributed genome hypothesis also posits that chronic pathogens utilize the distribution of non-core genes among strains of a species as a survival strategy, whereby the continuous recombination of genetic characters between strains serves as a supra-virulence factor that improves population survival through the generation of new strains with novel combinations of genes. Thus, this population-level gene reassortment acts as a counterpoint to the adaptive immune response of vertebrates, providing a means for pathogens to constantly present the host with novel antigens obtained from any of the constituent species of the symbiome.


What makes pathogens pathogenic.

Ehrlich GD, Hiller NL, Hu FZ - Genome Biol. (2008)

The distributed genome hypothesis. (a) Schematic showing the distributed (non-core) genes of a species supragenome in a population pool with individual strains below each containing the same set of core genes (green helix). (b) Schematic showing each of the strains of a species with the core genome and a unique distribution of non-core genes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2481411&req=5

Figure 1: The distributed genome hypothesis. (a) Schematic showing the distributed (non-core) genes of a species supragenome in a population pool with individual strains below each containing the same set of core genes (green helix). (b) Schematic showing each of the strains of a species with the core genome and a unique distribution of non-core genes.
Mentions: The distributed genome hypothesis [35,36] states that bacterial pathogens arise and acquire virulence traits primarily via horizontal gene transfer (Figure 1). More recently, it has become clear that many bacteria are multicellular organisms during part of their life cycle [37], and this has led to the recognition that bacteria possess a number of virulence traits that are expressed only at the population level and are not operational at the single-cell level [38]. These hypotheses are based on the observation that nearly all classes of pathogenic bacteria maintain highly energy-demanding mechanisms for accessing foreign DNA [39], in spite of the fact that most of these species maintain small genomes. The importance of this observation is that in a background of processes that favor gene deletion [40], the maintenance of multiple horizontal gene transfer mechanisms indicates that these traits are highly selected for. The distributed genome hypothesis also posits that chronic pathogens utilize the distribution of non-core genes among strains of a species as a survival strategy, whereby the continuous recombination of genetic characters between strains serves as a supra-virulence factor that improves population survival through the generation of new strains with novel combinations of genes. Thus, this population-level gene reassortment acts as a counterpoint to the adaptive immune response of vertebrates, providing a means for pathogens to constantly present the host with novel antigens obtained from any of the constituent species of the symbiome.

Bottom Line: Metazoans contain multiple complex microbial ecosystems in which the balance between host and microbe can be tipped from commensalism to pathogenicity.This transition is likely to depend both on the prevailing environmental conditions and on specific gene-gene interactions placed within the context of the entire ecosystem.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Genomic Sciences, Allegheny General Hospital, Allegheny Singer Research Institute, Pittsburgh, PA 15212, USA. gehrlich@wpahs.org

ABSTRACT
Metazoans contain multiple complex microbial ecosystems in which the balance between host and microbe can be tipped from commensalism to pathogenicity. This transition is likely to depend both on the prevailing environmental conditions and on specific gene-gene interactions placed within the context of the entire ecosystem.

Show MeSH
Related in: MedlinePlus