How could you make a lambda lysogen of a Gal- strain that is also deleted of the maltose gene activator so that it is λ r ? You might try infecting with lambda phage containing φ80 tail fibers, but...

How could you make a lambda lysogen of a Gal- strain that is also deleted of the maltose gene activator so that it is λ^r
? You might try infecting with lambda phage containing φ80 tail fibers, but the cells are φ80r as well as resistant to all other lambdoid phage and their host range mutants. The conditions of the problem are to make the lysogen in one step. Transducing the cells to make them Mal⁺
and then lysogenizing them is forbidden.