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. In another embodiment, there is disclosed a method of eliminating a microbial contaminant, the method comprising: obtaining one or more lytic enzymes produced by a mutant bacteriophage； applying the one or more lytic enzymes to a bacterial contaminant, without prior infection of the bacterial contaminant with a bacteriophage, to eliminate the bacterial contaminant.
