Bacteriophages Phi 8 and Phi 12 host infection are inhibited by OMVs and LPS purified fromP. pseudoalcaligenesstrain: East River Isolate A

Abstract

AbstractCystoviridaeis a family of double stranded RNA (dsRNA) phage that infects various strains ofPseudomonas syringae, a Gram-negative soil bacteria known to infect various crops. Surrounding the icosahedral capsids of these phages is a bacterial derived phospholipid membrane. Embedded within this membrane is a multi-component protein complex, referred to as the spike complex. The spike complex is responsible for host recognition and membrane fusion. We studied the ability of two members of theCystivirdaefamily to infect cells in the presence of purified outer membrane vesicles (OMVs) and lipopolysaccharide (LPS) derived from distinct sources. In this study we determined that OMVs from the hostPseudomonas pseudoalcaligenesstrain: East River isolate A (ERA) inhibit Phi 8 and Phi 12 host infection. These OMVs range in size from 30 to 60 nm and bind to Phi 8 and Phi 12. However, OMV purified fromP. syringaepv. phaseolicola LM2691 andE. coliΔyciBΔdcrBdid not inhibit Phi 8 or Phi 12 host infection. However, LPS derived from ERA and LM2691 inhibited Phi 8 and Phi 12 infection, demonstrating that LPS is the receptor for these two viruses, and that OMV biogenesis is selective of LPS. LPS derived from other non-CystoviridaeGram-negative bacteria, did not inhibit infection. We confirmed that host proteins are not required for Phi 8 or Phi 12 host interaction. Our results also suggest that differences in lipid A and the core polysaccharide in LPS may influence Phi 8 and Phi 12 host binding.IMPORTANCEMost phage families studied to date use a tailed appendage, composed of a multitude of proteins, for cellular recognition, membrane penetration, and genome injection. This contrasts with members of theCystoviridaefamily which possess a phospholipid membrane bilayer with embedded proteins responsible for cellular recognition and membrane fusion. Thus, theCystoviridaeare akin to enveloped viruses which also use protein complexes embedded into their membrane for cellular recognition and membrane fusion. Examples of such viruses include theRetroviridae, Coronoviridae, Herpesviridae, andOrthomyxoviridaefamilies. The binding specifics ofCystoviridaeto the host outer membrane are unknown. UsingCystoviridae-OMV interaction we began to uncover the host requirements for bindingCystoviridae. The results presented determine that only lipid A and the core polysaccharide of LPS are required forCystoviridaeouter membrane binding.