Bacteriophage GIL01, infecting Bacillus thuringiensis serovar israelensis, possesses a linear dsDNA genome of 14,931 bp with proteins attached to its 5' extremities and terminal inverted repeats at both ends. Viral particles are sensitive to organic solvents, suggesting that a lipid membrane is present in the capsid. All these characteristics are reminiscent of those found in members of the Tectiviridae family. Sequence analysis of GIL01 revealed the presence of two open reading frames (ORF25 and ORF30) encoding potential lytic enzymes, which were cloned and overexpressed in Escherichia coli. The muralytic activity of these two proteins, designated Mur1 and Mur2 respectively, was confirmed in situ using renaturing sodium dodecyl sulfate (SDS)-polyacrylamide gels containing bacterial cell wall preparations. While Mur2 degrading activity is limited to B. thuringiensis israelensis, Mur1 has a broader cleavage spectrum.