Endo-N-acetylneuraminidase associated with bacteriophage particles

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Abstract
A bacteriophage (.vphi. 1.2) was isolated for Escherichia coli K235 (O1:k1:H-). .vphi.1.2 is specific for the host capsular polysaccharide (colominic acid). The phage forms plaques with acapsular halos and thus, carries a glycanase activity for colominic acid, a homopolymer of .alpha.(2 .fwdarw. 8)-linked N-acetylneuraminic acid (NeuNAc) residues. Upon incubation with purified .vphi.1.2 particles, a solution of K1 polysaccharide loses viscosity and consumes increasing amounts of periodate. By gel filtration, the production of colominic oligosaccharides (down to a size of 2-3 NeuNAc residues) can be demonstrated. No NeuNAc monomers are formed. The capsules of E. coli strains with the K92 antigen, which consists of NeuNAc residues linked by alternating .alpha.(2 .fwdarw. 8) and .alpha.(2 .fwdarw. 9) bonds, are also depolymerized by the .vphi.1.2 enzyme. By EM, phage .vphi.1.2 belongs to Bradley''s morphology group C; it has an isometric head carrying a baseplate with 6 spikes. By analogy to other virus particles with host capsule depolymerase activity, the .vphi.1.2 endo-N-acetylneuraminidase activity is probably associated with these spikes.