Bacteria use a variety of defence systems to control bacteriophage infection, amongst others extracelluar vesicles (EVs) [1, 2, 3]. Such EVs demonstrate a proficient capacity to bind and reduce the number of infectious bacteriophage particles within a bacterial population [2]. However, the precise mechanism underlying the interaction between vesicles and bacteriophages is still not fully understood. Outer membrane vesicles (OMVs) of Gram-negative bacteria like Salmonella (S.) contain a variety of surface receptors used in bacteriophage infection. Bacteriophage infection or antibiotic treatment triggers vesicles production [3]. We have recently shown that phage P22 binds to S. Typhimurium OMVs and injects its DNA into the vesicle lumen [2]. Aim of this study is to analyse the properties of these "phage infected" OMVs. We employed P22 bacteriophages carrying GFP-genes as reporters for successful Salmonella infection to study the fusion between OMVs and bacteria and explore potential new mechanisms of gene transfer between bacteria and phages. Here, we also want to study the fate of bacteriophage particles that have ejected their DNA but remain bound to the OMV surface. We compare different OMVs obtained from full membranes or isolated from culture supernatants under different conditions, and characterize them in complex with phages using dynamic light scattering, fluorescence spectroscopy and electron microscopy.

[1] Adam Kulp and Meta J Kuehn. Biological functions and biogenesis of secreted bacterial outer membrane vesicles. Annual review of microbiology, 64:163–184, 2010.

[2] Mareike S Stephan, Nina K Broeker, Athanasios Saragliadis, Norbert Roos, Dirk Linke, and Ste-fanie Barbirz. In vitro analysis of O-antigen-specific bacteriophage P22 inactivation by Salmonella outer membrane vesicles. Frontiers in Microbiology, 11:510638, 2020.

[3] Ethan Hicks, Nicholas MK Rogers, Christine Ogilvie Hendren, Meta J Kuehn, and Mark R Wiesner. Extracellular vesicles and bacteriophages: New directions in environmental biocolloid research. Environmental Science & Technology, 57(44):16728–16742, 2023.