In this project, we are developing in vitro systems to study the interactions between Salmonella phage particles and host outer membrane as well as rates of DNA ejection from the viral capsid to understand initiation of the infection and how different phage tail architectures influence this process [1]. We use total internal reflection fluorescence microscopy (TIRF-M) to observe bacteriophages on supported lipid bilayers (SLBs) that contain LPS or fragments of native Salmonella outer membranes. Phage particle tracking on these SLBs yields quantitative information on particle attachment and detachment and on their diffusive behavior [2]. We characterize membrane compounds and SLBs with dynamic light scattering, TIRF-M and quartz crystal microbalance with dissipation monitoring. Moreover, we analyze DNA release from phages in presence of various membrane systems with fluorescence spectroscopy and TIRF-M. We observed that phage mobility on host membranes changed over time, with populations showing varying mobility, most probably a consequence of receptor depletion on the surface due to enzymatic activity of the phage tailspikes. In addition to provide information on the mechanism of infection initiation, model systems of the Gram-negative outer membrane will allow to connect the single phage particle behaviors to biological effects such as competition of phages within a phage cocktail.

[1] Andres D et al. (2012) Tail morphology controls DNA release in two Salmonella phages with one lipopolysaccharide receptor recognition system. Mol. Microbiol. 83: 1244-1253.

[2] Bally M et al. (2021) Physicochemical tools for studying virus interactions with targeted cell membranes in a molecular and spatiotemporally resolved context. Anal Bioanal Chem, 413:7157-7178.