Abstract
Bacteriophages, host-dependent replicative non-cellular entities which significantly shape the microbial genomes and consequently physiological and ecological properties of the microbial populations are exploited to restrict plant, animal and human pathogens. Unravelling of phage characteristics aids the understanding of the basic molecular mechanisms of phage infections which can subsequently lead to the development of rationalized strategies to combat microbial pathogens. In an unbiased screen to investigate the molecular basis of infectivity of the fire blight pathogen Erwinia amylovora by the lytic Schitoviridae phage S6, the biofilm extracellular matrix component cellulose has been identified as a cyclic di-GMP dependent first receptor required for infection with the phage to possess beta-1,4-glucosidases to degrade the exopolysaccharide. This absolute receptor dependency allows maintenance of a phage-microbe equilibrium with a low bacterial density.