The mutation that allows it to produce this (and to survive it) is a naturally occurring one. This strain, with that mutation, was found in the wild, which was what gave rise to the idea to use it in this way in the first place. One of the modifications they _did_ do was to break this bacteria's lateral gene transfer machinery so that it can't spread these genes to other strains.

However it is likely that, since this one strain managed to evolve this trait, that others have as well.