Small RNAs in Bacterial Outer Membrane Vesicles

Abstract

Outer membrane vesicles (OMVs) from Gram-negative bacteria exhibit selective enrichment for small RNAs (sRNAs), including tRNA fragments, as opposed to randomly reflecting cellular RNA pools. Building on well-established RNase-detergent controls and ddRTPCR quantification, we summarise delivery stoichiometry (≈1% of vesicle RNA reaching recipient cytoplasm) and propose reporting standards (vesicles per cell, RNA copies per vesicle, delivery per cell). Functionally, OMV RNAs signal via two main routes: cytosolic Argonaute-dependent silencing and endosomal TLR7/8 sensing in both pathogenic and commensal bacterial species. We highlight evidence that OMVs can travel along the gut–brain axis and activate astrocytic NF-κB, thereby exacerbating amyloidassociated pathology, and we outline the experimental controls needed to attribute these effects specifically to RNA cargo. Finally, we consider how these principles could guide the engineering of probiotic-derived OMVs to tune immune tone within a quantitative mechanistic framework. This review identifies key methodological gaps and puts forth quantitative frameworks for studying RNA delivery.