Morphological features and lipopolysaccharide attachment of coliphages specific to Escherichia coli O157:H7 and to a broad range of E. coli hosts

Abstract

The objective of the present study was to analyze host-phage adsorption of bacteriophages infecting Escherichia coli O157:H7 and the other E. coli strains. Out of 55 coliphage strains, we selected seven coliphages infectious only to 23 E. coli O157 and seven other coliphages of broad specificity to E. coli O157:H7 and other 61 E. coli. Escherichia coli O157-specific phages and the broadly specific phages all belonged to the Siphoviridae and Myoviridae family, respectively. Escherichia coli O157-specific phages infected E. coli O157:H7, but not E. coli O157:H7 Delta rfaL, deletion mutant of O-antigen ligase gene for lipopolysaccharide. Five coliphages among the broadly specific phages infected E. coli O103, but not E. coli O103 Delta rfaG, deletion mutant of the glycosyltransferase gene. E. coli O157:H7-specific phages among Siphoviridae recognized O-antigen of E. coli O157, but the broadly specific coliphages of Myoviridae may recognize O-antigen and/or a part of the lipopolysaccharide core as an adsorption site in various E. coli. The receptor of the two coliphage groups interacts with some part of lipopolysaccharide, and the tail morphology of the coliphages may be related to their adsorption to and recognition of a different part of lipopolysaccharide. In particular, specificity of E. coli O157:H7-specific phages carrying the long tail of Siphoviridae for O-antigen as a receptor seems to be high.