Fig. 4. Temporal and spatial control of phage infectivity by ion thresholds in terrestrial ecosystems.

A Major cytoplasmic ion concentrations as a function of diffusion distance from lysed E. coli cells compared with EC₅₀ concentrations required for T4 phage infection (dashed lines) B Major ion concentrations in a typical Sierra Nevada spring water during evaporation as a function of concentration factor compared with phage EC₅₀. Concentration factor is the ratio of the initial volume of water to the volume remaining after evaporation. Colors are consistent between EC₅₀ and ion concentration lines. Colors and symbols are the same as in panel A. C Conceptual model for phage infection. Ionic strength in freshwater environments is too low to promote phage infection. Higher ionic strength is found in metazoan guts or brackish/marine waters and transiently observed in drought influenced soils or in a biofilm adjacent to a lysed cell. When other strains (blue) are present, such as when the dominant electron donor/carbon source or other niche dimensions shift, fewer productive phage:host interactions will proceed.