| Shigella spp.,the causative agent of human shigellosis,released outer membrane vesicles(OMVs)with the diameter of 50-200nm.To gain an overview of the pathogenicity-associated functions that S.flexneri exports via OMVs,we performed comparative proteomics analysis of protein profiles between OMVs originally either from wild type or virulence plasmid-cured S.flexneri 2a 301 grown at 30℃ or 37℃,respectively.In all four OMV preparations,total 591 vesicular proteins were identified.There are rich in COG categories of translation,ribosomal structure and biogenesis(15%),and Cell wall/membrane/envelope biogenesis(12%).OMVs derived from wild type strains specifically enclosed a large number of T3SS effectors.OMVs derived from virulence plasmid-cured strains enriched metabolism-related proteins specifically.OMVs derived from strains grown at 30℃ specifically enriched a large number of amino acid metabolism-related proteins.While OMVs derived from strains grown at 37℃ specifically packaged Hfp,which is a virulence regulatory protein.Furtherly,bacterial invasion assay combined with OMV showed that wild type S.flexneri 2a 301 were up to 3.5 times more invasive with the presence of OMVs from wild type S.flexneri 2a strain 301 grown at 37℃,while excess OMVs from virulence plasmid-cured strains grown at 30℃ reduced the invasiveness of wide type strains significantly.Taken together,we speculate that OMVs enclose and transport specific cargo molecules,which would participate in the regulation of bacterial virulence directly or indirectly,such as 20 T3SS effectors detected in OMVs from wild type S.flexneri 2a strain 301 grown at 37℃ and the two unique moleculars of H-NS and DamX in OMVs from virulence plasmid-cured strains grown at 30℃.Altogether,those selective cargo proteins detected in our study can serve as the groundwork for further disclosing OMV’s role in bacterial pathogenesis and understanding of host-bacterium interaction. |
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