I've chanced upon a passage that is not entirely clear to me:
In addition to conjugation, transformation and transduction, other less well recognised mechanisms of DNA uptake occur in nature, while other mechanisms of HGT are probably yet to be elucidated, in particular, DNA uptake by eukaryotes:
Vesicle-mediated translocation by a range of gram-negative bacteria such as Neisseria gonorrheae, E. coli and Pseudomonas aeruginosa, which can bud off vesicle structures that contain genetic material (e.g.antibiotic resistance and virulence genes) and then fuse with another bacterium (Dorward et al., 1989; Kadurugamuwa and Beveridge, 1997; Yaron et al., 2000).
(From "Risks from GMOs due to Horizontal Gene Transfer", by Paul Keese)
Is it the bacteria that fuse with another bacterium, or is it the vesicles that fuse another bacterium? I'm not sure.
I thought the vesicles were budded off in the first place so that they could carry gene material to another bacteria.
(asked a parallel question at ELL SE)