We have examined the nature of the role played in the process of phage lambda DNA injection by the bacterial protein coded by the ptsM/pel gene. Neither the specific inhibition of the activity of the PtsM protein, nor the addition of inhibitors of phosphotransferase system modified the efficiency of lambda DNA penetration. Thus, the PtsM/Pel protein does not seem to play a role through its transport function, although we have confirmed that it must be present for a successful lambda DNA injection. Moreover, the presence of various metabolic inhibitors (uncouplers, cyanide, arsenate) separately or together, or even harsher methods of energy depletion did not prevent lambda DNA penetration, suggesting that DNA is entering the cell cytoplasm by diffusion.