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Comparative genomic analysis uncovers 3 novel loci encoding type six secretion systems differentially distributed in
Carlos J Blondel1, Juan C Jiménez, Inés Contreras
1Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile. cblondel@ciq.uchile.cl
BMC Genomics
|August 6, 2009
Summary
Researchers identified three novel Type VI Secretion System (T6SS) loci in Salmonella genomes, suggesting independent evolution and adaptation to diverse environments. An evolved VgrG protein indicates a new role for T6SS in bacterial killing.
Area of Science:
- Microbiology
- Genomics
- Bacterial Pathogenesis
Background:
- The Type VI Secretion System (T6SS) is a critical protein secretion mechanism in bacteria.
- Previous studies identified a T6SS in Salmonella Pathogenicity Island 6 (SPI-6), but only examined limited Salmonella genomes.
Purpose of the Study:
- To identify novel T6SS loci in Salmonella by analyzing all available genome sequences.
- To understand the distribution and evolutionary history of T6SS in Salmonella.
Main Methods:
- In silico analysis of 44 Salmonella genome projects.
- Comparative and phylogenetic analyses of T6SS loci.
Main Results:
- Identified three novel T6SS loci: SPI-19, SPI-20, and SPI-21.
- SPI-19 found in specific S. enterica serotypes; SPI-20 and SPI-21 in S. enterica subspecies arizonae.
- Discovered an evolved VgrG protein in SPI-21 with a pyocin domain, and identified "evolved Hcp" proteins.
Conclusions:
- Salmonella T6SS loci were acquired through independent lateral gene transfer events.
- T6SS likely contributes to serotype adaptation to various environments and hosts.
- The evolved VgrG suggests a novel role for T6SS in interbacterial killing.
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