Phage effect in liquid culture. (A) Growth of PAO1 measured in CFU/ml in liquid over 48h. In the absence of phage, PAO1 grows normally (solid green lines). When phage are added, population size of PAO1 (dashed green lines) decreases over the first few hours, but then increases again, resulting in an increasingly resistant population. The phage population measured in PFU/ml (gray lines) increases accordingly. (B) PA14, which is naturally resistant to the phage, grows similarly in the presence or absence of phage (dashed or solid red lines, respectively), while phage populations (gray) remain approximately constant.  (C) When PAO1 (green) and PA14 (red) are grown together in co-culture in the absence of phage, PAO1 grows worse than alone. (D) When the phage is added to the co-culture, PAO1 population size drop below the detection limit at 6 hours and do not recover. (E) PAO1 is grown together with phage at different initial population sizes. At the end of the experiment, bacteria are plated onto agar plates saturated with phage or PBS to count the resistant population and the total population. A starting population size greater than ~104 allows resistance to emerge. (F) Population size of PAO1 depends on the starting population of PA14. Here, initial population size of PAO1 was always 106, while initial PA14 numbers varied as one the x-axis. Once PA14 became too numerous in the population (greater than ~106), PAO1 could no longer maintain its population size high enough to evolve resistance to the phage.