Abstract: There is disclosed a method of engineering bacteriophages comprising: identifying a bacteriophage with only one attachment gene; isolating said bacteriophage; removing said attachment gene from the genome of said bacteriophage; and inserting a non-natural attachment gene into the genome of said bacteriophage wherein said non-natural attachment gene is specific for attaching to a selected bacteria. There is also disclosed a mutant bacteriophage comprising a heterologous nucleic acid sequence encoding a first specific attachment gene, the first specific attachment gene being different than an inactivated attachment gene and being specific for a selected bacteria.