Abstract: The present invention related to a method for producing or propagating an engineered bacteriophage, comprising the steps of: providing a functional synthetic genome of an engineered bacteriophage being able to infect a target bacterium; providing a recipient bacterium; transforming the recipient bacterium with the functional synthetic genome in a transformation step, yielding a transformed recipient bacterium; incubating the transformed recipient bacterium in a first incubation step, wherein the engineered bacteriophage is propagated within the transformed recipient bacterium; and further incubating the transformed recipient bacterium or the propagated engineered bacteriophage released from the transformed recipient bacterium with the target bacterium in a second incubation step, wherein the propagated engineered bacteriophage infects the target bacterium and is further propagated within the target bacterium, and wherein the recipient bacterium is a cell wall-deficient bacterium.