Formation of phage lysis patterns and implications on co-propagation of phages and motile host bacteria
Fig 1
Sector-shaped lysis patterns emerge due to nutrient depletion.
(a) Schematic of experimental procedure. Bacteria, phages, and a saline control were spotted on swim plates and incubated for 14 h, which resulted in the development of the sector-shaped lysis pattern. (b) Time evolution of the lysis pattern in experiment vs. model. (c) Interactions between key processes in the model. Pointed arrows: positive influences. Blunt arrows: negative influences. (d) Quantitative comparison of bacterial and phage densities between experiment (yellow bars) and model (red bars). In the experiment, areas labeled by yellow numbers were sampled for phage and bacterial quantifications (see Methods). Corresponding areas in the model are labeled by red numbers. (e) Simulated density of total bacteria. The dashed green outline of the bacteria-dense area is superimposed on (f-m) for reference. (f) Simulated density of infected bacteria. (g) Simulated density of phages. (h) Simulated nutrient concentration (per unit area). Right: Orange curve shows the nutrient concentration profile along the axis of symmetry of the lysis pattern (blue dashed line in left panel). (i) Simulated phage production rate. Active phage production only happens at the outer edge of the lysis area. (j) Simulated spatial flux of total bacteria. (k) Intensity of bacterial spatial flux (~ length of arrow in (j)). Bacteria are motile only at the outer edge of the swim ring. (l) Simulated spatial flux of infected bacteria. (m) Intensity of spatial flux of infected bacteria (~ length of arrow in (l)). Infected bacteria are only motile at the outer edge of the lysis area. The spatial flux shown in (j-m) represents the sum of diffusion flux and chemotaxis flux. Length of the arrow is proportional to magnitude of the spatial flux. (e-m) present snapshots of model simulation at 10 h, an intermediate time at which the colony expansion and pattern formation progress steadily.