Project SummaryMicrobial communities are dynamic and are influenced by a broad suite of biotic and abiotic factors.One of the most important factors providing structure to microbiomes are direct interactions amongmembers of these communities and therefore a deeper understanding of the molecules produced byand which affect other microbes as well as resistance mechanisms to these molecules will greatly informour ability to engineer microbial communities. Bacteriocins are molecules produced by bacterial cellsthat are thought to specifically target different strains of the same species or closely related species.Tailocins are a subset of bacteriocins coopted from phage tails which are durable possess highlyspecific killing activities maintain one-hit-one-kill dynamics and appear to be effective prophylactictreatments for preventing bacterial invasion of plants. The Baltrus lab has broadly characterized a classof phage derived bacteriocins produced by the plant pathogen Pseudomonas syringae as well as otherPseudomonads and we show that the host range of some of these molecules is broader than originallythought in that they can target some human pathogens that are often found associated with plants.Specifically we have discovered that Pseudomonas sp. 43A maintains tailocin-like killing activityspecifically against E. coli O157:H7 and not against a variety of other E. coli or Salmonella strains.Experiments within this proposal will confirm and characterize the genetic basis of this tailocin-likekilling of E. coli O157:H7. Overall experiments within this proposal could allow for fine scaleengineering to enable tailocins to specifically and effectively target human pathogens associated withplants while avoiding off target effects associated with other agricultural antimicrobial treatments.