Phage host interactions reveal LPS and OmpA as receptors for two Erwinia amylovora phages

Erwinia amylovora is the causative agent of fire blight. Resistance to streptomycin, the main antibiotic in fire blight management, has led to an urgent requirement to develop alternative biological control agents, such as the phage-carrier system (PCS). Previous studies have focused on the dynamic interactions between the carrier (Pantoea agglomerans), lytic phages, and the pathogen. However, crucial information about phage receptors on these hosts is still lacking. Here, a biochemical approach was used and the phage receptors of two E. amylovora phages (ϕEa21-4 and ϕEa46-1-A1) on both hosts, have been identified as LPS and OmpA on E. amylovora and OmpA only on P. agglomerans. Interestingly, this work uncovered for the first time that amylovoran is tightly attached to the LPS of E. amylovora. Confirmation of this interaction and an infection model are presented that have far reaching implications for additional PCS improvement and pathogen-host interaction details.