Comment on "High-Resolution Microscopical Studies of Contact Killing Mechanisms on Copper-Based Surfaces".

In the original paper, Chang and co-workers describe the contact killing of Bacillus subtilis , a Gram-positive bacterium, on copper-containing substrates and offer a mechanism for its accomplishment. The present Comment offers support for that mechanism and adds a necessary initial step, the degradation of the overlying peptidoglycan lattice. Degradation is necessary because the lattice is too thick, and its pores too small, for substrate-membrane contact without it. A suggestion is offered as to how degradation is accomplished.