The development of a proteogenomic pipeline to characterize the type VI secretory system (T6SS) of Gram-negative bacteria — ASN Events
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The development of a proteogenomic pipeline to characterize the type VI secretory system (T6SS) of Gram-negative bacteria (#156)

Jacqueline A Melvold 1 , Piklu Roy Chowdhury 1 2 , Matt P Padula 3 , Steven P Djordjevic 1 2 , Ian Charles 1
  1. ithree institute, University of Technology, Sydney, Ultimo, NSW, Australia
  2. New South Wales Department of Primary Industries, Camden, NSW, Australia
  3. Proteomics Core Facility, University of Technology, Sydney, Ultimo

The type VI secretion system (T6SS) is a recently described bacterial export pathway that has been characterised in a range of Gram-negative organisms. The pathway is involved in the export of a variety of effectors that can target both prokaryotic and eukaryotic cells.  While bioinformatic analysis of sequenced genomes shows that T6SS elements appear widespread in nature with 25% of Gram-negative bacteria harboring 1 or more copies, functional analysis has only been carried out for a handful of organisms. The functional data that has been published shows that the T6SS exhibits an impressive sophistication and complexity. Importantly, the T6SS has been shown to be involved in bacterial pathogenesis of clinically important pathogens, such as Escherichia coli, Vibrio cholerae and Pseudomonas aeruginosa.

In order to understand the biological significance and role played by T6SS elements in cell-to-cell interactions, we have carried out a proteogenomic characterisation of the T6SS from Shewanella algae (S. algae) grown under a diverse range of growth conditions. Genomic analysis of S. algae identified the presence of a T6SS with high homology to that of O1/O139 serotype Vibrio cholerae.  To investigate the activity of this T6SS, the SA1 proteome was harvested following growth on a range of complex media (LB broth, LB agar, blood agar, blood heart infusion broth and TCBS agar) and investigated utilizing 1D-SDS-PAGE and LC-MS/MS.  The results demonstrate that the expression of T6SS proteins in S. algae are differentially expressed and can be activated via growth on solid media containing components derived from eukaryotic cells. This systems biology approach allows us to present a comprehensive multi-genome analysis of genetic loci harbouring gene clusters constituting the key differentially regulated T6SS elements.

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