Spheroplasts of the genera Escherichia, Salmonella, Aerobacter, Proteus, and Serratia can be infected by T4 phage which have been exposed to 6 M urea. The interaction between the phage and the bacteria does not require either phage tail fibers or the specific tail fiber receptors of the bacteria. These findings imply two modes of infection, one of which may precede the other, in the normal phage infection process. Transformation of T4 phage by denatured DNA fragments has been demonstrated with Aerobacter as the host organism. In Aerobacter, transformation is more efficient than in Escherichia, and at low DNA concentrations Aerobacter yields 100-fold more transformed phage than Escherichia. © 1969.