Outer membrane vesicles induce the mussel plantigrade settlement via regulation of c-di-GMP

The study of extracellular vesicles (EVs) has the potential to identify unknown cellular and molecular mechanisms in intercellular communication and in organ homeostasis and disease. Exosomes, with an average diameter of ~100 nanometers, are a subset of EVs. The biogenesis of exosomes involves their origin in endosomes, and subsequent interactions with other intracellular vesicles and organelles generate the final content of the exosomes. Their diverse constituents include nucleic acids, proteins, lipids, amino acids, and metabolites, which can reflect their cell of origin. In various diseases, exosomes offer a window into altered cellular or tissue states, and their detection in biological fluids potentially offers a multicomponent diagnostic readout. The efficient exchange of cellular components through exosomes can inform their applied use in designing exosome-based therapeutics.

Outer-membrane vesicles (OMVs) are spherical buds of the outer membrane filled with periplasmic content and are commonly produced by Gram-negative bacteria. The production of OMVs allows bacteria to interact with their environment, and OMVs have been found to mediate diverse functions, including promoting pathogenesis, enabling bacterial survival during stress conditions and regulating microbial interactions within bacterial communities. Additionally, because of this functional versatility, researchers have begun to explore OMVs as a platform for bioengineering applications. In this Review, we discuss recent advances in the study of OMVs, focusing on new insights into the mechanisms of biogenesis and the functions of these vesicles.

Most bacteria release membrane vesicles (MVs) that contain specific cargo molecules and have diverse functions, including the transport of virulence factors, DNA transfer, interception of bacteriophages, antibiotics and eukaryotic host defence factors, cell detoxification and bacterial communication. MVs not only are abundant in nature but also show great promise for applications in biomedicine and nanotechnology. MVs were first discovered to originate from controlled blebbing of the outer membrane of Gram-negative bacteria and are therefore often called outer-membrane vesicles (OMVs). However, recent work has shown that Gram-positive bacteria can produce MVs, that different types of MVs besides OMVs exist and that, in addition to membrane blebbing, MVs can also be formed by endolysin-triggered cell lysis. In this Review, we provide an overview of the structures and compositions of the various vesicle types and discuss novel formation routes, which may lead to distinct vesicle types that serve particular functions.