Surface exposure and packing of lipoproteins into Outer Membrane Vesicles are coupled processes in Bacteroides.

ABSTRACT: Outer membrane vesicles (OMV) are spherical structures derived from the outer membrane (OM) of Gram-negative bacteria. OMVs from the predominant gut microbiota members, Bacteroides, are proposed to play key roles in gut homeostasis. OMV biogenesis in Bacteroides is a poorly understood process. Here, we revisited the protein composition of B. theta OMVs by mass spectrometry. We confirmed that OMVs produced by this organism contain large quantities of glycosidases and proteases, with most of them being lipoproteins. We found that many of these OMV-enriched lipoproteins are encoded by polysaccharide utilization loci (PULs), such as the sus operon. We examined the subcellular localization of the components of the sus operon and found that the alpha-amylase SusG is highly enriched in OMVs while the oligosaccharide importer SusC remains mostly in the OM. We show that all OMV-enriched lipoproteins possess a lipoprotein export sequence (LES) that mediates translocation of SusG from the periplasmic face of the OM towards the extracellular milieu and is required for SusG to localize preferentially to OMVs. We also show that surface-exposed SusG in OMVs is active and can rescue growth of bacterial cells incapable of growing on starch as only carbon source. Our results support the role of OMVs as "public goods" that can be utilized by other organisms with different metabolic capabilities.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Bacteroides Fragilis

SUBMITTER: Nichollas Scott  

LAB HEAD: Mario Feldman

PROVIDER: PXD011378 | Pride | 2018-11-04

REPOSITORIES: Pride