Figure 4.
Mechanisms of generating mechanical force, helping bacteriophages to penetrate the O-antigen shield of E. coli. (A) Molecular motors, driven by processive polysaccharide depolymerization or deacetylation (for example, phage N4, P22-like viruses, G7C-like viruses). Vertical arrows: mechanical force generated; (B) movement of the tail components of certain podoviruses upon primary receptor recognition (as in phage SU10); (C) deployment of the STFs of T-even-related phages. (D) Piercing of the OPS layer by the tube of the contractile tail of long-tailed myoviruses (phage P1); (E) pulling the tail tube through the OPS by folding of the CTF in siphoviruses (for example, phage T5).