Acquisition, co-option, and duplication of the rtx toxin system and the emergence of virulence in Kingella
The bacterial genus Kingella includes two pathogenic species, namely Kingella kingae and Kingella negevensis , as well as strictly commensal species. Both K. kingae and K. negevensis secrete a toxin called RtxA that is absent in the commensal species. Here we present a phylogenomic study of the genu...
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Veröffentlicht in: | Nature communications 2023-07, Vol.14 (1), p.4281-4281, Article 4281 |
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Zusammenfassung: | The bacterial genus
Kingella
includes two pathogenic species, namely
Kingella kingae
and
Kingella negevensis
, as well as strictly commensal species. Both
K. kingae
and
K. negevensis
secrete a toxin called RtxA that is absent in the commensal species. Here we present a phylogenomic study of the genus
Kingella
, including new genomic sequences for 88 clinical isolates, genotyping of another 131 global isolates, and analysis of 52 available genomes. The phylogenetic evidence supports that the toxin-encoding operon
rtxCA
was acquired by a common ancestor of the pathogenic
Kingella
species, and that a preexisting type-I secretion system was co-opted for toxin export. Subsequent genomic reorganization distributed the toxin machinery across two loci, with 30-35% of
K. kingae
strains containing two copies of the
rtxA
toxin gene. The
rtxA
duplication is largely clonal and is associated with invasive disease. Assays with isogenic strains show that a single copy of
rtxA
is associated with reduced cytotoxicity in vitro. Thus, our study identifies key steps in the evolutionary transition from commensal to pathogen, including horizontal gene transfer, co-option of an existing secretion system, and gene duplication.
The bacterial genus
Kingella
includes pathogenic species that secrete a toxin called RtxA, which is absent in commensal species. Here, Morreale et al. identify key steps in the evolutionary transition from commensal to pathogen, including horizontal gene transfer of the toxin-encoding genes, co-option of an existing secretion system, and gene duplication. |
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ISSN: | 2041-1723 2041-1723 |
DOI: | 10.1038/s41467-023-39939-8 |