(645d) Dynamics of Phage-Bacteria Interactions in Crowded Environments

Bacteriophages (i.e., “phages”) are viruses that infect, replicate in, and ultimately kill bacteria. As such, phage-bacteria interactions play a key role in determining microbiome formation and functioning, with critical implications for agriculture, food production, and medicine. However, studies of these interactions typically use “well-mixed” cultures in test tubes or Petri dishes, which do not mimic many of the complexities of natural habitats. For example, in nature, bacteria and phages often exist in crowded 3D environments such as soil and biological tissue, where spatial heterogeneity and interactions with their surrounding environment fundamentally alter their behavior. Furthermore, phage-bacteria interactions are typically studied at a limited number of timepoints due to the experimental challenges of real-time analysis, further limiting understanding of how they influence microbiomes in practice.

Here, we address this gap in knowledge using direct visualization of phage-bacteria interactions in transparent crowded matrices composed of packed hydrogel microparticles (i.e., “granular hydrogels”). Specifically, we use confocal microscopy to visualize the real-time dynamics of motile E. coli encountering lytic T4 phages as a function of the initial spatial distribution of the bacteria and phages, the initial phage and bacterial concentrations, and the degree of confinement imposed by the crowded hydrogel matrix (i.e., the amount of space available to move in the surrounding 3D environment). Ultimately, by directly visualizing these interactions in crowded spaces more akin to natural habitats, our work will provide new quantitative insights to inform the design of phage-based engineering solutions across disciplines.