Introduction
The history of research into extracellular vesicles (EVs) is an example of how a single term can delay the development of an entire scientific field. The commonly used word 'debris' is a nonspecific collective designation of all undefined extracellular particles and its negative tone suggests that all such particles represent cellular waste. For a long time, this connotation discouraged scientists from investigating extracellular particles in depth, thus obscuring the discovery of both EVs and non-EV nanoparticles in this compartment. However, after several decades of sporadic observations of extracellular, membrane-enclosed structures, the early 2000s brought a renewed research focus on these EVs, leading to an exponential development of the field in the past two decades. The designation 'extracellular vesicles' was suggested in 2011 as a collective term for lipid bilayer-enclosed, cell-derived particles. EVs are released by all cellular organisms. For example, the release of outer membrane vesicles by Gram-negative bacteria and the more recently described discharge of cytoplasmic membrane vesicles by Gram-positive bacteria and archaea demonstrate that EV production is characteristic of all three domains of life (archaea, bacteria and eukaryota). The broad term of bacterial extracellular vesicles is increasingly used to refer to all EVs released by bacteria.
