It was also apparent that maximum killing left a small number of E. coli survivors and a second dose of fresh V52 was unable to eliminate the prey organisms (Fig. 2B and Fig. S2). We are currently exploring explanations for why E. coli prey was not completely eliminated. Possible explanations include the development of resistance among a small group of E. coli prey; alternatively, the minority of prey following extensive bacterial reduction could make contact extremely unlikely, allowing for a small number of E. coli to evade predation.