Exercise 2

Which modifications are essential for phage binding?

Answer – For phage to bind to the C. jejuni cell, the β-d-GalfNAc residue must have the MeOPN group covalently bound. This binding can be perturbed by modification of adjacent residues, blocking phage-bacterial interactions.

Which genes encode the enzymes for each modification? As a result, which phasotype matches to which modification (A-E)?

Answer – cj1421 adds the MeOPN to C-3 of the β-d-GalfNAc residue. cj1422 transfers the MeOPN to C-4 of d-glycero-α-l-gluco-heptopyranose. cj1426 was demonstrated to encode the 6-O-Me transferase enzyme.

  • 1-0-0 = A
  • 1-1-1 = B
  • 0-1-1 = C
  • 0-0-1 = D
  • 1-0-1 = E

Using the answers above, what is the phenotype of the 1-0-0 phasotype?

Answer – Cells with the 1-0-0 phasotype would be extremely sensitive to phage infection. The cj1421 gene (in the on phase) would add the MeOPN group to β-d-GalfNAc, which is essential for phage binding. In addition, as the other genes are in the off state, there would be no modifications on the adjacent residues to perturb phage binding.

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