Bacteria-host interaction

To understand the origin and emergence of pathogenic bacteria, knowledge of the genetic inventory from their nonpathogenic relatives is a prerequisite.
Despite being considered nonpathogenic to its bovine host,the 2.11 Mb Wolinella succinogenes genome holds an extensive repertoire of genes identified in the related Helicobacter species and C. jejuni as virulence factors. These include genes for hemolysins and related proteins, adhesions and antigenicity factors, invasins and toxins as well as the neutrophil activating protein NAP.

One of the most striking examples is the secreted C. jejuni invasion antigen B (ciaB), which is essential for invading the host cell in the infection process.
Another key pathogenicity factor of Helicobacter as well as Campylobacter is the type IV secretion system that functions as a delivery system of biopolymers into a host cell.

Interestingly in Wolinella succinogenes we found orthologs of components assembling the type IV secretion apparatus encoded in Wolinella Genomic Island I (WsuGI I). The deviating GC content of 39%, the insertion into a tRNAmet locus and co-localisation of the Wolinella specific IS1302 elements provides clear evidence for an acquisition via horizontal gene transfer.
Remarkably, theWolinella Genomic Island I reveals an almost undisturbed synteny to the Campylobacter type IV system encoded on the virulence plasmid pVir. Via RT-PCR it could be shown that these type IV secretion genes are transcribed despite their different codon usage in congruence to multiple orthologs of the described virulence factors.

The differential expression profiles of Wolinella cells in absence or presence of host cells and in response to different cultivation conditions are studied on the transcriptomic and proteomic level using microarray technology, as well as 2D-gel analysis.
A categorization and comparison of the genomic inventory allows a prediction of the individual life styles of each organism.

Genes shared by all species are likely to be essential for their maintenance in a mammalian or vertebrate host, allowing a general strategy for the survival and growth, as well as common mechanisms for spread and transmission into larger host populations.

Genes unique to a species will likely provide insight into biological functions that distinguish symbiotic or commensal versus pathogenic modes of infection and confer host and tissue specificity.

Interestingly, a large proportion of the species-specific genes can be shown to co-localize in the individual genomes, despite the fact that no genome wide co-linearity is observable among these closely related genomes.

The finding that the non-pathogenic W. succinogenes groups large numbers of virulence factors and fitness gene homologs suggests that these genes might not only be involved in pathogenic responses towards a host but might also be involved in maintaining a symbiotic or commensal relationship with a host.
The largest gain in understanding host specificity of these bacterial organisms will result from analyzing the 20-35% of predicted genes that are specific to each of the organisms and do not show any homology to sequences already deposited in the databases.

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