Bacteria use a variety of defence systems to control bacteriophage infection, amongst others extracelluar vesicles (EVs) [1, 2, 3]. In particular, bacteriophage infection or antibiotic treatment trigger vesicle production [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. The tailed S. Typhimurium-specific phages P22 (podovirus), 9NA (siphovirus), and Det7 (myovirus) use lipopolysaccharide as a receptor. 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 characterise these "DNA loaded" OMVs and to analyse their properties. We study the change in the surface composition of the OMVs upon phage challenge with emphasis on their LPS composition. We also investigate the fate of bacteriophage particles bound to the OMV surface. For this, we compare different OMVs obtained either from explosive cell lysis or when budded into culture supernatants. We characterise 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