Beta phage is seen in
High-Yield Explanation
The toxigenicity of the diphtheria bacillus depends on the intracellular presence of corynephages (tox+), which acts as genetic controlling toxin production. Non-toxigenic strains are rendered toxigenic by infecting them with the beta or some other phages This is known as lysogenic or phage conversion. REF:Textbook of microbiology; Ananthanarayan and paniker's; 10th Edition; Pg: 240