Abstract
Many Gram-negative bacterial species release outer membrane vesicles (OMVs) that interact with the host by delivering virulence factors. Here, we report for the first time that RNA is among the wide variety of bacterial components that are associated with OMVs. To characterize the RNA profiles of bacterial OMVs, we performed RNA deep sequencing analysis using OMV samples isolated from a wild type Vibrio cholerae O1 El Tor strain. The results showed that RNAs originating from intergenic regions were the most abundant. Our findings reveal a hitherto unrecognised feature of OMVs mimicking eukaryotic exosomes and highlight a need to evaluate the potential role of RNA-containing bacterial membrane vesicles in bacteria-host interactions.
Highlights
Studies of bacterial outer membrane vesicles (OMVs) have revealed some similarities with vesicles known as exosomes that are secreted by most mammalian cell types
Their similarity to eukaryotic exosomes and the fact that OMVs act as transporters of various bacterial constituents prompted us to investigate if an “exosome-like” RNA delivery system by bacterial OMVs exists
The 3D volume of the purified vesicles was analysed by cryo-electron tomography and interestingly revealed that larger vesicles comprised double membranes (Fig. 1B). These OMVs may appear similar to bacterial minicells which are achromosomal particles derived from bacterial cells with mutations inactivating
Summary
Detection of RNA associated with V. cholerae A1552 vesicles. OMVs from the wild type V. It suggested that the release of RNA from the bacterial cells in association with OMVs was not growth phase dependent. To clarify whether or not the detected RNA was tightly associated with the vesicles and not appeared there due to co-precipitation of somehow released RNA, e.g. from lysed bacterial cells during ultracentrifugation steps, OMVs were purified using an Optiprep density gradient centrifugation procedure as described in the Materials and Methods. Ultrapure RNA was extracted from A1552 whole cells and from vesicles, Size Size/Total size Regiona) Region/Total size Intergenic regionb) Intergenic region/Region Up- or downstream region Up- or downstream region/Region Uncharacterizedc) Uncharacterized/Region Characterizedd) Characterized/Region Membrane associatede) Membrane associated/Region Membrane associated/Characterized Cytoplasmicf) Cytoplasmic/Region Cytoplasmic/Characterized sRNA sRNA/Region
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