Amino acid alterations in Gp38 of host range mutants of PP01 and evidence for their infection of an ompC null mutant of Escherichia coli O157:H7.

The previously isolated T-even type coliphage PP01, specifically infective to Escherichia coli O157:H7, uses the outer membrane protein OmpC as a receptor. The characterization of a spontaneous PP01-resistant strain indicated that it had lost ompC due to the deletion of a 14-kbp region upstream of and partially including ompC. Two host range mutants, able to infect an ompC null mutant, were isolated. Sequencing of gene 38, which codes for the receptor recognition protein Gp38, indicated three mutations in one mutant and two in the other. Both mutant proteins had a Gly208Arg, a Gly161Arg or Gly101His replacement, respectively, and the one mutant phage in addition a Trp189Arg replacement. These alterations suggest that the host range was mediated by a more positively charged Gp38.