Figure 2.

The population dynamics of phage T3 (A), T4 (B), T5 (C) and T7 (D) phage with T7-selected mucoid E. coli MG1655 as the host strain in LB. A total of three independent cultures were diluted 1:100 into fresh LB media every 24 h, and CFU/PFU estimates of the densities of bacteria and phage were made by serial dilution plating. Solid lines show bacterial densities in each replicate (red/green/blue); dotted lines show the phage densities in the corresponding cultures. Phage-free cultures (black and purple lines) are shown as controls, to indicate resource-limited population density for the bacteria. Phage-free controls lost the mucoid phenotype entirely by the end of the 4th serial transfer. At the end of the 15th serial transfer, three colonies from each phage-infected culture were streaked at least three times to get rid of phage, yielding non-mucoid revertants that were again sensitive to the relevant phage.