Lack of lysogenic induction in "diaminopimelic acid spheroplasts"

As part of an attempt to develop a semi-in vitro system of lysogenic induction, using spheroplasts of Escherichia coli K-12 lysogenic for prophage lambda, we prepared spheroplasts by depriving E. coli dap of diaminopimelic acid (DAP-spheroplasts). DAP-spheroplasts made from E. coli (lambda cI857) were thermally inducible. However, DAP-spheroplasts of E. coli (lambda) were not inducible by UV light. Thus, it appears that a functional cell wall is required for UV induction of prophage lambda.