Host Exopolysaccharide Quantity and Composition Impact Erwinia amylovora Bacteriophage Pathogenesis
ABSTRACTErwinia amylovorabacteriophages (phages) belonging to theMyoviridaeandPodoviridaefamilies demonstrated a preference for either high-exopolysaccharide-producing (HEP) or low-exopolysaccharide-producing (LEP) bacterial hosts when grown on artificial medium without or with sugar supplementation.Myoviridaephages produced clear plaques on LEP hosts and turbid plaques on HEP hosts. The reverse preference was demonstrated by mostPodoviridaephages, where clear plaques were seen on HEP hosts. Efficiency of plating (EOP) was determined by comparing phage growth on the original isolation host to the that on the LEP or HEP host. Nine of 10Myoviridaephages showed highest EOPs on LEP hosts, and 8 of 11Podoviridaephages had highest EOPs on HEP hosts. Increasing the production of EPS on sugar-supplemented medium or decreasing production by knocking out the synthesis of amylovoran or levan, the two EPSs produced byE. amylovora, indicated that these components play crucial roles in phage infection. Amylovoran was virtually essential for proliferation of mostPodoviridaephages when phage population growth was compared to the wild type. Decreased levan production resulted in a significant reduction of progeny from phages in theMyoviridaefamily. Thus,Podoviridaephages are adapted to hosts that produce high levels of exopolysaccharides and are dependent on host-produced amylovoran for pathogenesis.Myoviridaephages are adapted to hosts that produce lower levels of exopolysaccharides and host-produced levan.