DNA uptake by cell wall-deficient bacteria reveals a putative ancient macromolecule uptake mechanism

Horizontal gene transfer in bacteria is widely believed to occur via three main mechanisms: conjugation, transduction and transformation. These mechanisms facilitate the passage of DNA across the protective cell wall using sophisticated machinery. We present here a new mechanism of DNA uptake that is independent of canonical DNA uptake machineries and is used by bacteria that live without a cell wall. We show that the cell wall-deficient bacteria engulf extracellular material, whereby intracellular vesicles are formed, and DNA is internalized. This mechanism is not specific to DNA, and allows uptake of other macromolecules and even 125 nm lipid nanoparticles (LNPs). Uptake was prevented by molecules known to inhibit eukaryotic endocytosis, suggesting this to be an energy-dependent process. Given that cell wall-deficient bacteria are considered a model for early life forms, our work provides a possible mechanism for primordial cells to acquire new genetic material or food before invention of the bacterial cell wall.