For most of the time scientists have known about them, the tiny membrane bubbles that Gram-negative bacteria constantly pinch off and release were filed under metabolic byproduct. Debris. Something cells do that does not obviously matter.
They matter. Each bubble is a nanoscale sphere of bacterial membrane carrying proteins, lipids, nucleic acids, and toxins. Because they are built from the same material as the parent cell, they cross tissue barriers efficiently. Because they carry bacterial surface molecules, the immune system notices them immediately. And because they cannot replicate, they behave more like a package than an infection.
