The invention encompasses phage φmru including phage induction, phage particles, and the phage genome. Also encompassed are phage polypeptides, as well as polynucleotides which encode these polypeptides, expression vectors comprising these polynucleotides, and host cells comprising these vectors. The invention further encompasses compositions and methods for detecting, targeting, permeabilising, and inhibiting microbial cells, especially methanogen cells, using the disclosed phage, polypeptides, polynucleotides, expression vectors, or host cells.