Multiple adsorptions shape collective T-even phage lysis dynamics: Insights from an individual-based model

Bacteria infected by T-even bacteriophages exhibit a variety of multiplicity of infection (MOI) dependent behaviours, including lysis from without (LO), cell lysis induced by an exceptionally high number of secondary adsorptions, and lysis inhibition (LIN), a phenomenon in which host cell lysis is delayed as the same bacterium adsorbs multiple phages. We propose an individual-based model that captures these MOI-dependent dynamics phenomenologically. The model takes into account the development of LO resistance (LOR) after the primary infection, and LIN is modelled by a fixed average delay in latent period per secondary adsorption with stochastic variability. The model successfully reproduces the experimentally observed multiple peaks in phage production following controlled phage addition. We extend the model to simulate batch culture growth and demonstrate that synchronized collapse of LINed culture can emerge as a collective phenomenon when LOR cells have a high, but finite, LO threshold (LOR cell lysis from withOut, LORO). Finally, we apply the model to a spatially structured bacterial colony under phage attack. We find that, if the burst size is comparable to the LO thresholds, especially LORO may play a role in colony survival due to locally elevated MOI near lysing cells. These results highlight the importance of spatial dynamics and secondary adsorption thresholds in phage-host population outcomes.